The Garden Shed
A Community Newsletter published by the Piedmont Master Gardeners
December 2021-Vol.7, No.12
For comments, questions or suggested topics for future Garden Shed articles contact us at: garden-shed@piedmontmastergardeners.org.
If you have specific gardening questions or need help to solve a gardening problem, our Horticultural Help Desk is a free community resource and can be contacted at 434-872-4583 or by email: albemarlevcehelpdesk@gmail.com.
Who We Are
We are members of the Piedmont Master Gardeners, which simply means we have all been trained to share the scientific expertise of Virginia Tech and the Virginia Cooperative Extension Service. More important, we are your friends and neighbors with a passion for gardening – and learning more about it. MORE
Table of Contents
In the Edible Garden
Seedless Fruits and Vegetables. How Does That Happen?
Ever wonder how seedless fruits and vegetables are grown? Here are explanations for a few of our favorites.
Tasks and Tips
Now that the garden is put to bed for winter, make some time to learn about sustainable gardening techniques and review new vegetable hybrids that can help improve results next year.
In the Ornamental Garden
Ask questions and share comments on particular articles.
Tasks and Tips
The Ornamental Garden in December
Monitor your garden carefully as the weather changes; enjoy the holidays safely; and nurture your houseplants.
The Ornamental Garden in December
This monthly list of tips and tasks will cover three areas: outdoor garden care, holiday tips, and houseplant care.
OUTDOOR GARDEN CARE
- Take a walk around your landscape making notes about what you would like to add or subtract from your gardens next season. Make notes on thinning or transplanting perennials that have become overgrown.
- Consider repairing or adding hardscape projects.
- Look for areas in your landscape where water collects and make a note of the location and the degree of wetness before and after rain or snow. See this article for ideas on how to address drainage issues both large and small. Some approaches may be as simple as aerating, adding soil gradually as a top dressing, or planting water tolerant plants. Solutions to larger drainage problems might include regrading or redirecting runoff safely to a suitable area. This can be done using swales, French drains, catch basins or downspout extensions.
- Be aware of any plants that have already begun to heave with freezing and thawing; place them gently back into the soil to protect their roots.
- Remove spent foliage from perennials that are prone to fungal diseases such as Pulmonara (lungwort), peony, and hosta.
- Lay a 2-3” layer of mulch or leaves on perennial beds and shrubs after a hard freeze or when the soil temperature reaches 32°F.
- Pull mulch back from tree trunks.
- Loosen or removed matted layers of thick leaves.
- Clean garden tools with steel wool or a stiff wire brush, wipe with a damp cloth, dry, and apply an oil such as cooking oil, boiled linseed oil, tung oil, or WD 40.
- Shut off and drain outdoor water pipes and irrigation systems.
- Put away concrete bird baths, planters, rain gauges and other outdoor ornaments that might collect water and break in freezing temperatures.
- Plant spring-flowering bulbs before the ground freezes; although December may be late for bulb planting, it’s better to plant these bulbs now rather than waiting for spring. Mulch after planting to extend conditions for root growth.
- Provide food and water for the birds; be sure to change and clean water sources, clean bird feeders on a regular basis to avoid spreading disease.
- See this article from the National Wildlife Federation on how to provide water for birds in winter.
- Keep watering recently-planted trees and shrubs. Long, dry periods during fall and winter can cause injury or death to plant root systems.
- Continue to plant deciduous trees before the ground freezes. Your shovel will be unable to penetrate the soil if it is frozen. Avoid transplanting shrubs and trees on sunny or windy days, which can expose the roots to light and drying winds, stressing the plant. Mulch the area heavily to keep the ground thawed so roots can become established. See the November 2021 issue of The Garden Shed for helpful tips and a list of informational sources on planting trees.
INVASIVE PLANT CONTROL
With colder weather and holiday distractions, we may forget that invasive enemies are still at work. See this article from the Blue Ridge PRISM (Partnership for Regional Invasive Species Management) on identifying and treating invasive plants in winter.
HOLIDAY TIPS
TREES
Live tree or artificial? For some families, this is a question revisited each season. See this past article from The Garden Shed for key points to consider.
For tips on the selection and care of Christmas trees, plus a description of types of trees, see this article from NC State Extension.
Some people like to plant a living Christmas tree, either potted or balled-and-burlapped, into their landscape after the holiday season. For tips on selection and care of trees purchased for planting outside, see this article from NC State Extension.
General holiday tree care tips:
- If a tree has been stored out of water for three or more days, it is a good idea to make a fresh cut on the trunk prior to display. Remove a disk about half-inch thick to provide a clean fresh surface for water uptake.
- Use a tree stand with a large reservoir for water. The water level in the stand should be checked and replenished daily. If the tree stand is allowed to dry out, the tree may not readily take up water again. When trees dry out, they should be removed before they create a fire hazard.
- Do not turn on Christmas tree lights if you think your tree has become dry.
- Do not use any Christmas tree preservatives or other additives in the water. University research has repeatedly shown that water additives are not needed and, in many cases, aggravate foliage drying and needle loss. This is true for both commercial products and home remedies such as sugar, aspirin, and even VODKA!
- The tree should be set up away from sources of heat such as heat vents, space heaters, or fireplaces. Even setting a tree up in front of a south-facing window can dry a tree out if it spends the day in full sun and is watered inadequately.
HOLIDAY GREENS AND BOXWOOD BLIGHT
Be very mindful of the threat of boxwood blight when bringing any boxwood greens or boxwood wreaths into your home. For more information on boxwood blight, see “Boxwood Blight Alert” in the November 2018 issue of The Garden Shed, as well as information from the Boxwood Blight Task Force. Don’t unwittingly contribute to the spread of boxwood blight by carelessly tossing out boxwood greens used for holiday decorations. Err on the side of caution–double-bag boxwood greens securely and dispose of them in the landfill. Do not add them to the compost pile. Buy boxwood greens from licensed vendors that can provide a copy of their Boxwood Blight Cleanliness Program Agreement.
HOLIDAY PLANTS
Poinsettia is the plant most frequently identified with holiday decorating. Give this plant sun for at least ½ day; ideal night temperature is in the 50s to 60s. Keep the plant away from drafts, heat registers, and fireplaces. Soil should dry only slightly between thorough watering. Be sure to poke drainage holes in decorative foil or remove foil to keep the soil from becoming soggy.
After buying poinsettias, protect them from cold on the way home. Exposure to icy temperatures for even a few moments may cause injury.
Holiday cacti, including Thanksgiving and Christmas cacti, are other popular plants for the holidays. Preparation should begin 6-8 weeks before desired flowers. These conditions are recommended for best flowering:
- a cool night temperature of 50-55°F
- 13 hours of uninterrupted darkness (if the temperature is 55-70°F)
- 15 hours of darkness (if the temperature is above 70°F)
For more information on holiday cacti, see this past article from The Garden Shed.
Cyclamen is another holiday plant option. The houseplant, or florist’s cyclamen (Cyclamen persicum), is a tuberous potted plant that flowers during the winter months. It has lovely, heart-shaped green foliage mottled with silver. Blooms come in shades of white, pink, rose, purple, and red. Cyclamen prefers cool temperatures and bright indirect light. Ideal daytime temperatures are 60-65°F with night temperatures around 50°F. Cyclamen prefers to be kept moist, but not soggy. Water when the potting medium feels dry to the touch, and always water along the edge of the pot, or from below, to avoid causing the tuber to rot. Unlike many other houseplants in winter, cyclamen can benefit from periodic light fertilization.
Although they can be considered persnickety, the photos below show the same cyclamen that has bloomed continuously from 12/20 through 12/21 (and I hope beyond).
Cyclamen 2021 Photo: Susan Martin
Cyclamen 2020 Photo: Susan Martin
HOUSEPLANTS
- The growth rate of most houseplants will slow during the cooler temperatures and shorter days of the winter months. Reduce both fertilization and water until late April or May when new growth resumes.
- As nights become colder, back houseplants away from windows to prevent chilling injury.
- Excessive moisture from watering and humidity can cause oedema. This condition is caused by roots taking up more water than foliage can transpire. Leaf cells rupture, particularly on the undersides, leading to water-soaked patches that look corky and unsightly. This condition is easily curable if caught early. Reduce watering and humidity. Do not remove unsightly leaves since this can worsen the condition. Plants that are especially susceptible include cacti, succulents, orchids, and semi-succulents such as Peperomia.
- Check for pests such as aphids, spider mites, scale, whitefly, mealybugs, and thrips. See this article from the Missouri Botanical Garden for photos, ID, and treatment.
- Group plants together to increase humidity levels but leave sufficient space for air circulation.
- If grouping plants together, be aware that this may increase the potential for insects infecting neighboring plants. Monitor frequently.
- When you are away, place houseplants on trays or saucers of pebbles with water below the top surface of the pebbles. This technique can be used effectively for about 1 week.
- Pebble trays can also be used to increase humidity during the winter heating months.
Pebble trays Photo: Susan Martin
Enjoy the holidays and continue to find beauty in the winter garden!
SOURCES
The Garden Shed, “The Ornamental Garden in December” or “Tips and Tasks”: 2020, 2018, 2017, 2016
“Monthly Gardening Tips,” Piedmont Master Gardeners.
“Gardening by the Month,” Missouri Botanical Garden.
“Wet Yard — Solving Drainage Problems,” Northern Virginia Soil and Water Conservation District.
“Glossary – Solving Drainage and Erosion Problems,” Northern Virginia Soil and Water Conservation District.
“Oedema,” Royal Horticultural Society.
“Green Tips for the Holiday,” The Garden Shed (December 2018).
“Selection and Care of Christmas Trees,” NC State Extension.
“Selection and Care of Living Christmas Trees,” NC State Extension.
“Holiday Cactus Brings the Gift of Color,” The Garden Shed (December 2019).
“Boxwood Blight Alert, The Garden Shed (November 2018).
“Boxwood Blight Task Force,” VA Coop. Ext.
“Don’t Forget Water for Birds in the Winter!” National Wildlife Federation.
“Control of Invasive Plants in Winter,” Blue Ridge PRISM.
Featured Photo, “December in the Ornamental Garden,” by Susan Martin
Questions from Readers
After reading the March, 2021 newsletter article, “A Year of New-Home Landscaping and What I’ve Learned,” an astute reader asked the author, Susan Martin, if her position on adding nonnatives to the landscape had changed since her June, 2018 article, “Crape Myrtle–A Southern Icon Gets Even Better.” The Garden Shed staff saw this as an opportunity to open further discussion by sharing Ms. Martin’s answer. This also inspired us to launch a new feature, “Questions from Readers.” We invite you to use this forum to help us learn from one another. If you have questions about a particular topic, you can be sure that others do too! Write any questions or comments in the comments section following the article.
QUESTION:
Susan, really good article. But in a 2018 article about Crape Myrtles, you were questioning whether or not non-natives might not have a place in our landscapes. Now it seems as if you’ve jumped on the “All native” bandwagon. Do you still feel that a combination of natives and nonnatives might provide a pragmatic approach to helping nature?
ANSWER:
This is a very timely comment since I’ve been thinking a lot about the question of using nonnatives in the landscape. As we know from studies on Carolina chickadees (Desirée L. Narango, Douglas W. Tallamy, and Peter P. Marra, 2018), landscapes with less than 70% native vegetation do not support the survival of chickadees or their young. When I first heard Doug Tallamy quote the minimum 70% guideline, I was relieved to think that I could indulge my fondness for plants such as lilacs (childhood memories), lungworts, leadworts, and peonies, and still be a contributing member of the homegrown national park movement. However, the chickadee study went on to show that a landscape with 94% natives is even better for chickadee survival. When I wrote the 2018 article on crape myrtles to which you referred, I was concentrating on the issue of whether that nonnative was invasive. I considered the invasive aspect of nonnatives to be a primary concern, which it is. However, I had not yet fully appreciated the longer view of building an interactive environment based on the evolutionary relationship between native plants and the native insects that support them. I’m still learning about that.
In our landscape, I can observe lots of pollinator activity on nonnatives such as crape myrtle, Russian sage (Perovskia atriplicifolia), and the annual flowering plant, gomphrena. But there are now studies that are researching differences in nectar quality. Some plants offer nectar that is more beneficial to pollinators. I don’t know if the nonnatives I mentioned are offering high quality nectar. More importantly, even if we assume that the nonnative plants are producing highly beneficial nectar, their foliage still isn’t providing food for caterpillars. All three of those flowering nonnatives, however, are deer and drought resistant, and provide late-season, long-lasting bloom which is beneficial for pollinators.
As described in this article, we had moved into a home that had the barest of landscape plantings. It was a fairly clean slate, and I wanted to plant as many natives on that clean slate as possible. Two years later, however, we’ve found that the damage from deer browsing has been severe on most of the native shrubs we planted. American beauty berry (Callicarpa americana) has been a wonderful exception. Some viburnum species are more resistant than others. We’ve had to cage our V. dentanum, but V. nudum, both straight species and cultivars, have proved acceptably resistant. V. prunifolium was largely defoliated by the second day after planting. I will keep experimenting with native shrubs to find more that are deer resistant, but the deer damage has been discouraging to date.
Except for the fringe trees (Chionanthus virginicus), the native trees have not been browsed by deer, but the survival rate has been disappointing. It’s likely that the severe drought this summer had something to do with that. But I also think that the native tree stock that’s available is not always as hardy as more commonly requested nonnative trees. The selection of native trees seems limited, and the quality hasn’t been consistent. You can easily find red maples, for example, but other trees such as hornbeams (Carpinus caroliniana) and American smoke trees (Cotinus obovatus) are more difficult to find. This will most likely change with increased demand for native trees. Another Piedmont Master Gardener, who is an expert on natives, suggested that native trees and shrubs might be more particular about where they are planted and less adaptable to less-than-ideal growing conditions as compared to nonnatives and cultivars that have been bred to be robust.
Although I am learning more about the end goals of planting natives and how to achieve these goals, the unique characteristics of our individual landscapes offer practical challenges. For example, I am limited in our landscape to selecting deer-resistant plants that can tolerate full sun, all day. There is also the challenge of finding suppliers of good quality native plants, especially trees and shrubs, of sufficient variety. Native perennials are becoming much easier to find, especially in light of the Plant Virginia Natives campaign which has been reaching out to suppliers as well as educating home gardeners. You may have seen in area nurseries the red labels from this campaign highlighting plants that are locally native. The Northern Virginia plant natives campaign has been compiling a list of cultivars of locally native plants—including shrubs and trees—that provide ecological services similar to the straight species.
My goal is to have well over 70% natives but I have the “advantage” of planting new rather than replacing. I will still keep or even add some nonnative shrubs or perennials if they are deer resistant, well-suited to our challenging landscape conditions, and bring me joy. Naturally, the “joy bar” for selecting nonnative plants becomes higher as I discover more native plants that flourish on our site.
Dear Reader, many thanks for your careful reading, and for highlighting such an important area of study.
Featured Photo: by Hannah Wei, Unsplash
Seedless Fruits and Vegetables. How Does That Happen?
If flowering plants have evolved to complete their full life cycle and generate seed to continue the species, how can seedless fruits and vegetables exist? And how can they continue to be grown year in and year out without producing seed?
There are a few different forces at work. Let’s review a little bit of science, some natural processes, and the human interventions that are behind the growing of some of the seedless fruits and vegetables that we all enjoy.
The Science
Normally, a fruit forms after pollination of a flowering plant when the female ovary is fertilized by male pollen. Fertilization causes seed development. The fruit is actually the ovary that swells around the seed. Natural genetic mutations may cause fruit to develop in some plants without fertilization and therefore without producing seeds. This characteristic, development of fruit without fertilization, is called parthenocarpy.
Today’s seedless fruits and vegetables started with this natural mutation, followed by human recognition that seedlessness was an attractive trait. Then humans found ways to propogate that plant to preserve that characteristic.
Seedlessness has several attractive features. Seedless oranges, grapes and watermelons are less messy and more enjoyable to eat. Eliminating cucumber seeds eases digestion issues for many people. And seedlessness lengthens shelf life since seeds tend to encourage the fruits’ deterioration to hasten their dispersal into the world.
Because seeds draw nutrients from the plant, seedlessness can affect fruit characteristics like nutrients, sugar content, size, and time to maturity. These characteristics are typically improved over time by breeders.
Let’s look at some examples.
Oranges
“Cara Cara & Washington Navel Oranges” by Forest & Kim is licensed under CC BY 2.0
The seedless oranges we eat today derive from a seedless tree discovered by farmers in a Brazilian orange grove in the 1870s. They sent tree cuttings to the USDA which propagated the trees through grafting and rooting practices, starting the seedless navel orange boom in the US.
Today, seedless orange trees are grafted descendants of the original seedless orange tree– in essence, clones. When groves of these cloned trees are formed, and are self-pollinated, seedless oranges are the result. However, if a bee picks up pollen from a seeded orange tree in a neighboring grove and cross pollinates a “seedless” tree, seeds will develop. So, it takes both the parthenocarpic characteristic and self-pollination to produce seedless oranges.
Grapes
Seedless grapes. Photo: SliceOfChic, CC BY-NC-ND 2.0.
Seedless grapes have a similar but even longer history. They were originally discovered about 6,000 BC in the Mediterranean region. The seedless fruit appeared spontaneously, was recognized, and was propagated vegetatively through grafting and rooted cuttings.
With grapes, there are two different groups that we call seedless. One is parthenocarpic, meaning that the fruits develop without fertilization. The other is called stenospermocarpic, where fertilization actually occurs but seed development aborts and soft seed traces are left in the fruit. Stenospermocarpic varieties have the advantage of growing full-size fruit, while the parthenocarpic, truly seedless grapes, tend to be smaller.
Bananas
Seedless bananas. Photo: SliceOfChic, CC BY-NC-ND 2.0
Seedless bananas have a similar history going back several thousand years. Seedlessness started as a natural mutation from heavily seeded wild bananas (see featured photo at the top). We tend to think of bananas as a tree fruit but actually they are an herbaceous perennial that is propagated vegetatively by transplanting side shoots or suckers from the main plant. Selected breeding over many years has developed the sweet, seedless fruits we enjoy today.
Bananas highlight the risks of cloning in this fashion. Through the 1900s, until the 1950s, the predominant banana cultivar that was imported into the US was called the Gros Michel. Its lack of diversity made it susceptible to a fusarium fungus, called Panama disease, that destroyed banana plants in all growing regions. It was replaced with a disease resistant variety called Cavendish which now accounts for about 97% of banana exports. Unfortunately, there is a new variant of Panama disease called Tropical Race 4 (TR-4) that is harming Cavendish plants in several growing countries.
The Cavendish banana is at risk. Breeders are working to develop replacements. While bananas are not currently genetically modified (GMO) fruits, the banana problem has raised an important question — whether a genetic modification is a logical way to provide disease resistance while maintaining parthenocarpic traits and adding biodiversity.
Pineapples
Young pineapple: Photo: Missouri Botanical Garden PlantFinder
Pineapples are similar to bananas in that they are herbaceous perennial members of the bromeliad family. Each segment on the exterior of the fruit produces a flower. Pineapples are called a syncarp, meaning that multiple flowers fuse into a single fruit. However, they are seedless because they are self-incompatible. This means that when a single pineapple variety is grown isolated from other varieties, and self-pollinates, fertilization does not occur. The plants are propagated vegetatively through root division, budding and runners.
Cucumbers
Cucumbers and some squashes are different than the previous examples. For one thing they are annual plants that must be grown from seed every year. Parthenocarpy is induced into cucumbers in multiple ways. Breeders have developed hybrids that are naturally parthenocarpic, and grow fruits without fertilization. Also, parthenocarpy can be induced by applying growth hormones and pollen extracts.
To grow seedless fruits, female flowers of parthenocarpic varieties are covered or grown in greenhouses where pollination is prevented.
Interestingly, the small tender seeds that exist in some “seedless” cukes are viable and will germinate into productive plants.
Watermelons
Seeldess watermelon. Photo: TM Weddle, CC BY-NC-SA 2.0
Seedless watermelons have a different propagation process. Watermelon seed fertility is affected by varying the number of chromosomes in the seeds’ cells. Normal watermelons have 22 chromosomes, 11 coming from the ovary in the female flower and 11 from the male pollen. In 1939 a Japanese plant scientist determined that treating the leading ends of young vines with a chemical called colchicine, doubled the number of chromosomes in the plant to 44. When the female flowers from these plants are pollinated by pollen from a plant with the normal 22 chromosomes, the resulting plants have 33 chromosomes. The plants with 33 chromosomes produce fruit with a hard shelled seed that are collected and sold to produce seedless melons. When pollinated with pollen from a 22 chromosome variety, the result is melons with the soft white seed traces that are the “seedless” melons we enjoy.
This multi-step process for growing seedless watermelons is obviously quite expensive. It accounts for the higher prices for seedless vs seeded watermelons. However, since introduction to the US market in the 1990s, seedless watermelon breeders have steadily improved melon taste and consumers have steadily increased consumption. Currently, over 90% of commercial watermelon sales are seedless. Clearly, they are here to stay.
The Future: GMO Fruits?
% of US Crops that are GMO. Image courtesy of Dr P Byrne, Colorado State University Extension
IR=insect resistant, HT=herbicide tolerant, DT=drought tolerant, VR=Virus resistant. Summer squash should be VR, not HT. Non-browning apples and potatoes also approved.
Growers have been figuring out ways to produce seedless fruits by taking advantage of natural mutations for thousands of years. More recently we have developed ways to modify “normal” seeded plants through breeding and chemical application. The results are fruits that have practical and consumer appeal but are higher cost than natural fruits. In some cases, cloning has reduced diversity, increasing susceptibility to diseases and other environmental factors.
New technology provides a means to address many issues through genetic modification. To date, there is consumer pushback against fresh GMO products although GMO ingredients are widespread in processed foods. It will be interesting to see how this changes over time.
In the meantime, I hope that an increased understanding of how seedless fruits came to be increases your enjoyment of their various benefits.
Sources:
“Seedless Fruit is not Something New,” Michigan State Extension
“How do Seedless Fruits Arise and How are the Propogated?” Scientific American (2000)
“How are Seedless Grapes Grown,” Science ABC, https://www.scienceabc.com/eyeopeners/how-are-seedless-grapes-grown-parthenocarpy.html
“Producing Summer Squash Without Pollination,” Cornell University Extension, http://www.hort.cornell.edu/expo/proceedings/2014/Vine%20crops/Seedless%20squash%20Reiners.pdf
“Seedless Watermelon: How Do They Do That?” Michigan State University Extension, https://www.canr.msu.edu/news/seedless_watermelon_how_do_they_do_that
“Watermelon: A Brief History,” University of Missouri Extension, https://ipm.missouri.edu/MEG/2020/7/watermelon-DT/
“Growing Seedless Triploid Watermelons,” University of Nebraska-Lincoln Extension, https://extensionpublications.unl.edu/assets/pdf/g1755.pdf#:~:text=Seedless%20watermelons%20are%20triploid%20%283X%29%20which%20causes%20them,from%20one%20parent%20and%202X%20from%20the%20other
“The Cavendish Crisis,” Evergreen.edu, http://blogs.evergreen.edu/terroir-jahni/the-rise-and-inevitable-fall-of-cavendish/
“A Banana-Destroying Fungus Has Arrived In The Americas,” Smithsonian Magazine, https://www.smithsonianmag.com/smart-news/banana-destroying-fungus-has-arrived-americas-180972892/
“List of Bioengineered Foods,” USDA Agricultural Marketing Service, https://www.ams.usda.gov/rules-regulations/be/bioengineered-foods-list
“The botany of seedless fruits,” Science and Plants for Schools, https://www.saps.org.uk/saps-associates/browse-q-and-a/322-from-which-part-of-the-flower-do-seedless-fruits-develop
“GMO Crops, Animal Food and Beyond,” US FDA, https://www.fda.gov/food/agricultural-biotechnology/gmo-crops-animal-food-and-beyond
Help! I need somebody (for gardening advice)
We all need somebody to lean on
(Image credit: openclipart.org, artist jhnri4. Used under the Creative Commons Zero 1.0 License.)
Our horticultural help desks, in our obviously unbiased opinion, are fantastic tools for sharing gardening knowledge. The main help desk is staffed by Piedmont Master Gardener volunteers and can be reached at albemarlevcehelpdesk@gmail.com or 434-872-4583. Walk-ins are welcome! The Help Desk is located at the Virginia Cooperative Extension office in the Fifth Street Extended Albemarle County Office Building (460 Stagecoach Road). Hours are Mon./Wed./Fri. 9 AM – noon from October 15 – March 15, and daily 9 AM – noon the rest of the year.
We also have help desks at the Charlottesville City Market (1st/3rd Saturdays), the Crozet Farmer’s Market (2nd/4th Saturdays), and events like the Albemarle County Fair and our Spring Plant Sale. Our Events Calendar has information about these and other PMG goings-on.
What kinds of questions do we field at the Help Desk? In other words, what are the main issues faced by gardeners in our area? We use a “ticket” system to record questions and responses at our main help desk. The chart below shows the number of tickets in the 50 most common categories of questions. For the top 10, here are some brief thoughts, as well as links to resources:
10. Pruning and deadheading are critical for appearance and health. The health benefits can’t be over-emphasized! Pruning creates space for airflow around leaves and branches, reducing dampness and fungal growth. Prune to remove diseased areas, preventing pathogen spread. Finally, pruning can remove broken, awkward (i.e. likely to break), and rubbing branches. Deadheading is less critical for health, but can extend flowering seasons.
Keep clippers and saws sharp and clean. Disinfect with a 70% rubbing alcohol solution.
Resources:
Pruning Basics and Tools (VCE publication 430-455)
Pruning Deciduous Trees (VCE publication 430-456)
Pruning Evergreens (VCE publication 430-457)
Pruning Shrubs (VCE publication 430-459)
Stop Topping Trees! (VCE publication 430-458)
9. Weed control should use methods appropriate to the problem. Don’t pull out the flamethrower for some ground ivy – just pull it up, if possible. If chemicals are absolutely necessary, use Integrated Pest Management (IPM) techniques. When using herbicides, always follow the directions on the label and use personal protective gear.
Timing is key to weed control, regardless of method. Apply pre-emergent herbicides before, well, emergence. Remove flowering weeds before they go to seed. It’s always easier to tackle a few weeds now than to wait until they’ve spread (easier said than done, of course).
Resources:
2021 Pest Management Guide – Home Grounds and Animals (VCE publication 456-018)
Virginia Tech weed identification website
Noxious Weeds (Virginia Department of Agriculture and Consumer Services)
Pests in Gardens, Landscapes, and Turf: Weeds (University of California Integrated Pest Management)
8. Leaf spots have many causes: fungal and bacterial diseases, mites, and insects like aphids and thrips.
My work here is done. (Image © 2021 S. Christopher Stroupe)
The bad news is that once leaf spots appear, often little can be done. Prevention is better: remove dead plant material at the end of the season, prune to prevent dampness, and don’t wet leaves when watering. The good news is that leaf spots often are benign. Maple trees in particular are prone to “zonate leaf spot” in late autumn, after the leaves have done their job.
To identify causes and suggest remedies, we need the following: species/name, when spots appeared, environment (e.g. shady/sunny/moist), and clear pictures of the spots and the entire plant. We can look at samples under a microscope in the VCE office.
If needed, we can send samples to Virginia Tech’s Plant Disease Clinic for diagnosis. The cost is $35. A proper sample is essential! Collection instructions are towards the bottom of this website.
Resources:
2021 Pest Management Guide – Home Grounds and Animals (VCE publication 456-018)
Leaf spot diseases of trees and shrubs (University of Minnesota)
Aphids (Virginia Tech Publication 444-020)
Thrips in Greenhouses (Virginia Tech Publication 444-281)
Spider Mites (Virginia Tech Publication 444-221)
Insect and Mite Pests of Boxwoods (Virginia Tech Publication ENTO-42NP)
7. Invasive plants are, of course, best handled early. Learn to recognize seedlings of common invasives like Asian bittersweet and autumn olive. And be sure not to plant an invasive! Virginia maintains a list of invasive species, many of which are unfortunately still commercially available. Virginia also keeps a list of native alternatives.
Removal methods depend on the plant. Some, like Japanese stiltgrass, are easily pulled by hand. Others, like English ivy, are much harder to remove manually. Herbicides, judiciously applied, are good tools for large-scale removal – but aren’t necessarily the best tool: many plants, like English ivy, are resistant to foliar glyphosate application. Brushing herbicide on freshly cut stumps works well for trees and shrubs like tree-of-heaven (Ailanthus altissima). Before trying that, consult the detailed guidance on control methods and cautions at Blue Ridge PRISM Factsheets–Control Methods.
Persistence is key, no matter the method. Many invasives have deep root systems and resprout after cutting. Repeated mowing or weed-whacking, which eventually exhausts the roots, might be required.
Resources:
Exotic Invasive Plants (VCE publication 420-320)
Blue Ridge Partnership for Regional Invasive Species Management (PRISM) Factsheets
Virginia Department of Conservation and Recreation Invasive Species Factsheets
6. Tree/shrub transplant and care should start by picking the right plant for the right place. Match location with sun or shade tolerance. Avoid poorly-drained soil. Test the soil to ensure proper nutrition and pH. Plan ahead: will the tree/shrub interfere with other plants, or power lines? Will it be too close to buildings?
The best time to transplant is fall, winter, or early spring, during dormancy. Transplant into a hole 3-5x the root ball’s diameter, deep enough that the top of the roots are just above ground level (for heavy/compacted soils, a little higher). Backfill and water thoroughly.
Care mainly entails pruning, fertilizing, and irrigating. Sufficient – not excessive! – irrigation is especially important in the first year or two.
Resources:
Problem-free Trees for Virginia Landscapes (VCE publication 450-237)
Planting Trees (VCE publication 426-702)
Fertilizing Trees and Shrubs (University of Maryland publication)
How to Evaluate a Tree (VCE publication SPES-313P)
5. Insect/tick ID is important because many insects are beneficial. Handle pests using suitable methods. Some ticks, like the deer tick that spreads Lyme disease, are worse than others.
The Help Desk can identify insects and ticks from physical samples (prepared according to these guidelines) and clear photos. Virginia Tech’s Insect ID Lab (idlab@vt.edu) is a great resource. Google Image Search – can be helpful; simply describe the bug – and reverse image search (click the camera icon and upload a picture).
Resources:
Insect Identification and Diagnosis Request (VCE publication 444-113)
4. Soil testing is always a good idea. Collect a representative sample by mixing sub-samples from about 10 spots. Sample boxes and submission forms are in a plastic box outside the VCE office (460 Stagecoach Rd., Charlottesville). Clients must mail samples to the lab themselves. Results will be emailed.
Test results include a soil amendment plan. Sometimes these are hard to follow – or it’s unclear what kinds of fertilizer are needed – so don’t hesitate to contact the help desk after receiving the results.
Pay particular attention to pH recommendations. Availability of many soil nutrients depends on pH. Calcium is a classic example: low pH impairs calcium uptake, so squash and tomatoes may show blossom-end rot even in calcium-rich clay soil if the pH is too low.
Resources:
Virginia Tech soil testing lab
Sample information sheet for submission
3. Tree/shrub browning or decline is a common question because there are many causes: root damage/disease, environmental stress (e.g. cold/heat/drought/salt), circulatory system (i.e. phloem/xylem) diseases, and diseases directly affecting leaves.
Outcomes also vary. Drought damage can usually be reversed, and salt damage is typically superficial. Root damage, e.g. from construction, might be survivable if it isn’t extensive and doesn’t lead to disease. Root and circulatory diseases, however, are likely fatal if untreated. Leaf spots, as discussed above, are often not serious. However, “Discula” anthracnose on dogwoods causes widespread leaf browning and eventually death.
Prevention is always better than cure. Plant disease-resistant varieties. Maintain vigor by pruning, watering, mulching, and fertilizing. Practice sanitation: remove leaf debris and prune using clean, sharp tools.
If necessary, we can send samples to Virginia Tech’s Plant Disease Clinic for diagnosis. The cost is $35. Collecting a good sample is critical! Instructions are at the bottom of this website.
Resources:
Tree Decline: What is it? (University of Missouri publication g5200)
Understanding Decline in Trees (Iowa State University publication SUL2)
Dieback and Decline of Trees (University of Tennessee publication SP686)
24 Ways to Kill a Tree (VCE publication 430-210)
2. Plant ID can usually be done electronically. Send clear pictures of as many parts of the plant as possible: leaves, bark, flowers, fruit. Also send pictures of the whole plant.
Google Image Search and reverse image search can be useful. Many websites and apps apply “artificial intelligence” to identify plants from pictures. (I have used Pl@ntNet, iNaturalist, and Flora Incognita.) Also helpful are “keys”, linked below, that use process of elimination.
Always feel free to bring samples to the office for closer examination! (Bring as many parts of the plant as possible.) Sometimes subtle differences in, for example, leaf vein patterns may be the key to identification.
Resources:
1. Boxwood browning/decline was our winner! This is a popular topic because, unfortunately, boxwoods suffer from many problems.
Boxwood blight symptom #2, black streaks on stems (image credit: Boxwood Blight Task Force, Virginia Tech)
Boxwood blight symptom #1, defoliation (image credit: Boxwood Blight Task Force, Virginia Tech)
Boxwood blight is the most notorious – so famous, it has its own taskforce. The identifying characteristics of boxwood blight are defoliation and black streaks on stems. (Other diseases, like Volutella, Colletotrichum, and Phytophthera root rot, leave dead leaves attached.) Boxwood blight is usually fatal.
Nematodes are also common. Nematodes attack roots, causing dieback and/or leaf discoloration. Leaves remain attached. Voles and moles also damage roots, causing similar symptoms. Mites, and insects like psyllids and leafminers, damage leaves, though usually not severely.
Finally, consider abiotic issues. Boxwoods can suffer cold damage, which usually causes browning on top of the plant. Drought/heat/salt damage can harm foliage.
Resources:
Best Management Practices for Boxwood Blight in the Virginia Home Landscape (Virginia Tech publication PPWS-29NP)
Insect and Mite Pests of Boxwood (Virginia Tech publication ENTO-42NP)
Selecting Landscape Plants: Boxwoods (Virginia Tech publication 426-603)
In conclusion, we hope everyone will feel free to call the Help Desk (434-872-4583), or send us an email (albemarlevcehelpdesk@gmail.com), with questions about any horticultural topic. It’s never too early to think about next year’s landscape project or vegetable garden – or how to get the most out of the plants you’re already growing!
Upcoming Events
The Virginia Soil Health Coalition is sponsoring a series of educational events in honor of World Soil Day, which is December 5th. To find out more and to register, check their website.
Living with Nature at Wintergreen Interpretive Hike: December 11, 1:00 pm
Join a Foundation Naturalist for an interpretive hike. These hikes are rated moderate. Payment due before event. FREE/Member, $8/Non-Member. For more information, Wintergreen Nature Foundation/Living with Nature.
Blue Ridge PRISM Winter Quarterly Meeting is coming up in early January
- January 5, 11:30 am – 1:00 pm.
For registration, see the PRISM website. At the meeting, there will be an update of recent PRISM activities by Rod Walker, Blue Ridge PRISM President, followed by a question and answer session featuring an expert panel on how to control invasive plants during the winter.
Becoming a Rivanna Master Naturalist
Two informational meetings in December:
- ZOOM meeting, Saturday, December 18, 10:00 AM
- LIVE meeting, Saturday, December 18, 11:00 AM, Ivy Creek Natural Area
- Applications due January 5, 2022
- Click here for the 2022 Class Master Naturalist informational flier!
Questions? COVID concerns? Contact rmncurriculum@gmail.com (Carol)
or call 434.996.8405 (Ida) if internet is a limitation.
Lewis Ginter Botanical Garden, Richmond:
Dominion Energy GardenFest of Lights
Open Daily November 22, 2021-January 9, 2022
(Closed Thanksgiving and December 24-25)
Advance online tickets with 30-minute arrival window required
See this LINK for more information and ticket pricing
The Edible Garden in December
Congratulations to everyone who had a successful edible gardening year in 2021. I hope you enjoyed the process of gardening as well as the fruits of your hard work. Also, that you have cleaned up your beds, planted cover crops or mulched them, and maybe are still harvesting some cool weather vegetables. In any case, now is the time to take a break from the physical work and begin thinking about next year.
Be Sustainable: Reduce Chemicals, Build Soil, Add Diversity
Admittedly speaking as an advocate, I suggest using the winter to learn about how to improve gardening practices and results next year through three principles:
- Reduce chemical use through Integrated Pest Management (IPM). IPM is a process based on observing pest issues, understanding them, taking action only when the damage is significant and using chemicals as a last resort. It requires looking past the surface of possible issues, a time commitment but also a learning experience. Given the obvious environmental damage from reflexive chemical use, it is important. For information about how to implement IPM, check out the Garden Shed article Integrated Pest Management
- Build your soil. Healthy soil can reduce the need for chemical pesticides and fertilizers. New insights about productive ways to do this are coming from the Regenerative Agriculture movement. It is a soil- focused approach to growing crops that advocates:
- Keeping the soil covered, with densely planted crops and employing cover crops or mulching in the off season
- Minimizing soil disturbance to preserve soil structure and keep weed seeds buried. This means minimizing tilling and depositing amendments on or near the surface, relying on soil organisms to carry them deeper,
- Keeping living roots in the soil to stabilize it while also improving structure and adding carbon-based nutrients.
- Add diversity by varying and rotating crops, interplanting, and utilizing diverse cover crops.
- Integrate livestock, or in their absence, add organic matter.
These practices have had positive results in commercial agriculture and provide guidance to home gardeners that is ecologically and horticulturally sound.
- Create a diverse home landscape, preferably of native trees, shrubs, and flowering perennials to help rebuild declining insect and bird populations. A healthy ecology helps manage garden pests naturally. Get guidance on how to create a pollinator-friendly landscape from the Garden Shed article Plant A Pollinator Paradise.
Other helpful information, including video material, is available in the references at the end of this article and on the Soil Health and Cover Crops page on the VA Cooperative Extension website.
As we realize how all levels of plant and animal life are built and dependent on each other, the need to return to more nature-based landscaping and gardening practices becomes compelling. Improving our approach in these three areas is a good start.
Other December Tasks
- As long as your soil isn’t frozen, it is still okay to plant garlic and shallots in December. Mulch them well to moderate temperature and moisture.
Open row cover. Photo: Ralph Morini
- Placing row covers over winter hardy vegetables adds several degrees to the temperature under the cover and protects plants in the event of extreme cold while encouraging continued growth into the winter. For tips on constructing simple hoop style row covers, consult The Garden Shed article Row Covers: A Season Extender with Benefits
- Put your leaves to good use.
Leaf-mulched herb bed. Photo: R Morini
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- Chopping or shredding leaves is a good idea to help speed decomposition, and improves water infiltration if used as a mulch for beds.
- They can be used to set up new compost batches with winter-generated kitchen plant scraps added as they become available. When spring temperatures rise into the 50’s, the batch’s carbon-to-nitrogen ratio can be fine-tuned to stimulate decomposition. With good moisture and aeration management, you should have compost ready for use prior to planting summer vegetables. Find guidance for home composting in the article Home Composting: A Guide for Home Gardeners, from the Penn State Extension.
- Leaves left in place provide cover for over-wintering beneficial insects and will help build a natural pest management system in your gardens next year.
- Be sure to drain your hoses. Disconnect them from faucets and lay them out on the ground, both ends open, to let them drain. Then roll them up for winter storage.
- Drain rain barrels and redirect downspouts to ground, rather than refilling the barrels during the cold months.
- December brings new catalogs and website updates from seed suppliers. It is fun to browse them, look for new items to grow, and to assess different varieties that may help avoid disease problems that affected last year’s garden. Pay attention to “time to harvest” and “disease resistance” data. For help interpreting seed catalog and seed pack information, check out the article Using Seed Pack Information to Help Your Garden Grow from the February 2018 issue of The Garden Shed.
- Make a first pass at laying out your crop arrangement for next year. Remember to rotate specific plants to different parts of the garden, preferably on a 3-4 year cycle. The benefits are both disease and pest reduction and soil enrichment through plant diversity.
- Care for your tools. Winter is the time to clean, disinfect, sharpen, and generally prepare them for the work ahead. Also a good time to clean pots and flats if you have a warm enough place to do the wet work. Come spring, you’ll be happy you did it.
- An enjoyable way to keep your hands in the soil during winter is to grow herbs indoors. You need a sunny window, preferably with a southern exposure. Use a premium potting soil and add nutrient as recommended. It’s best to use clean plastic or glazed containers to reduce watering requirements. Be sure the container has drainage holes and use a non-porous dish to catch excess water. Keep the soil surface moist between planting and germination. Herbs do best with temperatures above 65 degrees, the warmer the better. Basil likes temperatures above 70 degrees, so doesn’t want to be too close to the window during cold weather. Check out “Be Inspired With Indoor Herb Gardening” in the December 2020 Garden Shed for great information on growing herbs indoors this winter.
In any case, enjoy your gardening, happy holidays, and I hope to see you next month at The Garden Shed.
References:
“Cool Season Planting Chart for Companion, Interplanting and Square Foot Gardening,” Washington State University Extension: https://s3.wp.wsu.edu/uploads/sites/2056/2018/10/Cool-Season-Planting-Chart-for-Companion.pdf
Podcast: “Healing the Earth through Regenerative Farming,” Gabe Brown: https://www.youtube.com/watch?v=fFHnVgO0xPY
Video: “Nature’s Best Hope,” Dr. Doug Tallamy: https://www.youtube.com/watch?v=ZHURaRv78QY&t=9s
Virginia Native Plant Society website: Why Natives?: https://vnps.org/natives/