May Tasks in the Ornamental Garden
“I thought that spring must last forevermore;
for I was young and loved,
and it was May.”
The merry month of May, sometimes called the merry, merry month of May, is a wonderful time for gardeners. We have all that pent-up enthusiasm for digging in the dirt once again. Even weeding seems less of a chore. What should we do between Mother’s Day and Memorial Day to nurture the promise of May?
- Have fun with color! Plant warm-season annuals such as marigolds, zinnias, gomphrena, angelonia, and coleus.
- Look for drought-resistant plants that will ease watering duties once the hot, humid mid-summer arrives. Candidates include: catmint (Nepeta), purple coneflower (Echinacea purpurea), lambs ear (Stachys byzantina), yarrow (Achillea millefolium), goldenrod (Solidago), black-eyed Susan (Rudbeckia), sneezeweed (Helenium), and hyssop (Agastache).
- Try a new native plant for either sun or shade. Use locally-native plants that attract the most caterpillars to your landscape. The Native Plant Finder (By Zipcode) is a terrific online source for identifying these “keystone” native plants. For more information on this idea, see “A Year in New-Home Landscaping and What I’ve Learned,” The Garden Shed (March 2021).
- Sow seeds directly outoors. Candidates include: zinnia, cleome, cosmos, marigolds, morning glory, and sunflowers. When the plants reach 4-6” in height, pinch them back to promote bushier growth and increased flowering.
- Plant summer bulbs such as caladium, dahlia, canna lily, and elephant ears.
- If your area has a deer problem, use containers on a porch or deck for plants that you enjoy but don’t want to share with your white-tailed friends! Select a combination of different hostas, for example, or plant miniature roses.
- Pull weeds when they are small and the soil is moist. Know if weeds are annual or perennial. Pulling annual and biennial weeds can be effective if they are pulled BEFORE the plants go to seed. If weeds are too stubborn to pull without disturbing the soil, cut the tops off and apply an herbicide with a small brush to the cut stem. In established flower beds, weeds will be weakened by repeated cutting and lack of sunlight in crowded conditions under a taller plant canopy. Visit this publication for help with weed identification.
- Apply a 2-3” layer of mulch over the perennial bed in mid- to late spring, or when the ground warms and the soil has dried out from winter moisture. Mulch will help retain moisture and suppress weeds. Increase the density of garden plantings to reduce bare spots where weeds can take hold.
- Be aware of rain levels; provide adequate water for new bushes, trees, perennials, seedlings, and plants that have been divided or moved.
- Harden off seedlings for about 1-2 weeks before planting outside. Place seedlings in a protected spot outdoors (partly shaded, out of the wind) for a few hours each day, bringing them in at night. Gradually expose them to more sunshine and wind. Keep the soil moist at all times during this period.
- Snap off spent daffodil heads but do not remove the foliage; let the foliage brown as it stores food for next year’s flower production.
- Plan ahead by pinching back — pinch back chrysanthemums and asters to promote bushy growth; pinch back by about 1/3 in May, and once more before mid summer. July 4th is often used as an easy “cut-off” guideline for when to stop pinching back.
- Move houseplants outside into a shaded area once the danger of frost has passed and nighttime temperatures have stabilized to at least 50 degrees F. Gradually introduce the plants to more sun so that the bright sunlight doesn’t burn the foliage. Don’t forget to water!
- Start a habit of insect and disease patrol. Check leaves for insect damage, slug holes, Japanese beetle skeletonization, and signs of fungus.
- If you need help with identifying plant diseases or insect damage, and need advice about what to do, call the Piedmont Master Gardeners Help Desk at 434-872-4583 to speak with a Master Gardener volunteer or send an email to firstname.lastname@example.org. Office hours are Monday through Friday, 9:00 AM – 12:00 PM. The VCE Office is still currently closed to the public with hopes of reopening in mid-May. You can email photos of samples or drop them off outside our office for a Master Gardener to review. Visit our Help Desk page for more information.
FERTILIZING SHRUBS AND TREES
Many trees and landscape plants require little or no fertilizer once they are established and mature. When over-applied, fertilizers may aggravate insect and disease problems and force excessive growth which must be mowed or pruned. Excess fertilizers can run off yards into waterways or seep into aquifers, polluting drinking water.
The decision to fertilize should be based upon the health of the plant, the desired rate of growth, and a soil analysis. A soil analysis will tell you the soil pH and the amounts of nutrients in the soil that are available for plant growth. Soil pH affects the availability of nutrients in the soil. When fertilization is indicated by a soil test, you can then select a fertilizer that provides the nutrients that are lacking in the soil. Use slow-release fertilizers. Buy fertilizers that contain 50% or more of the nitrogen in slow-release forms. See “A Fertilization Primer: Plant Needs, Fertilizer Choices and Application Tips,” in the April 2021 issue of The Garden Shed.
SPRING PRUNING CONTINUES
Wait to prune until AFTER all flowers have faded. Examples of bushes to prune in May include: azalea (deciduous and evergreen), daphne (Daphne audora), fothergilla, forsythia, spring-blooming hydrangea, lilac, pieris (Pieris japonica), spring-blooming spirea, serviceberry (Amelanchier spp.), viburnum (deciduous and evergreen), pussy willow (Salix discolor), and spring-blooming witchhazel (Hamamelis vernalis). Hamamelis virginiana is a late-fall bloomer pruned in early spring.
If you’re wondering about the right time to prune a particular shrub, consult the Shrub Pruning Calendar published by the Va. Cooperative Extension, Coop.Ext. Pub.No. 430-462. For detailed instructions on how to prune shrubs, review Va.Coop.Ext. Pub. No. 430-459, and be sure to read A Pruning Primer/Garden Shed 2020.
MAY IS THE MONTH TO REMOVE INVASIVE SEEDLINGS
This information is provided by Blue Ridge PRISM (Partnership for Regional Invasive Species Management), 4/24/20.
The current weather pattern of intermittent rainfall (and, therefore, moist soil) has created ground conditions that are ideal for hand-pulling invasive plants. The key to hand pulling is being sure that you remove all or most of the roots, such that there is so little of the root system left in the ground that it cannot support regrowth.
Suitable targets are small, young sprouts of the following plants: English ivy (Hedera helix), climbing euonymous (Euonymous fortunei), Japanese honeysuckle (Lonicera japonica), Oriental bittersweet (Celastrus orbiculatus). Shrubs: Japanese barberry (Berberis thunbergia), multiflora rose (Rosa multifora), autumn olive (Eleagnus umbellata), Chinese privet (Ligustrum sinense), wineberry (Rubus phoenicolasius). Trees: Bradford Pear/Callery pear (Pyrus calleryana). Herbs: garlic mustard (Alliaria petiolata).
For photographs of each of these invasives and a description of how to pull weeds effectively, see this LINK from Blue Ridge PRISM.
THE TICKS ARE ACTIVE
In Virginia, the lone star tick (Amblyomma americanum) and the American dog tick (Dermacentor variabilis) are most active in May/June. Lone star ticks are found mostly in woodlands with dense undergrowth and around animal resting areas. The larvae do not carry disease, but the nymphal and adult stages can transmit pathogens causing monocytic ehrlichiosis, Rocky Mountain spotted fever and ‘Stari’ borreliosis. The lone star tick may also cause Alpha-gal syndrome, a type of food allergy to red meat and other products made from mammals. Female lone star ticks are easily recognized by a single white dot in the center of a brown body, with the males having spots or streaks of white around the outer edge of the body.
American dog ticks carry the rocky mountain spotted fever agent, and they can transmit it in the first few hours of attachment. Fortunately, the percentage of ticks carrying the agent is low, 1/1000 or 1/500. They can also transmit the disease tularemia. Adult males and females are active April to early August, and are mostly found questing in tall grass and low lying brush and twigs. Studies in Virginia found that when acorn crops are highest, mice and deer populations explode; soon after, the number of ticks and incidence of Lyme infection also soar.
When gardening, wear long pants and socks and make sure your pant bottoms are tucked into boots or socks or somehow fastened around your ankles. Wear long sleeves and tuck shirts into pants. Wear light-colored clothing, and check yourself carefully. See this LINK for a seasonal table of ticks in Virginia and tick-borne illnesses, as well as prevention tips. Also refer to The Garden Shed article, “Managing the Tick Problem.”
“Monthly Garden Tips – May,” Piedmont Master Gardeners, https://piedmontmastergardeners.org/gardening-questions/monthly-gardening-tips/#May
“Gardening by Month – May,” Missouri Botanical Garden, https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/gardening-by-month/may.aspx
“Common Turf Weeds,” Virginia Cooperative Extension, https://www.pwcgov.org/government/dept/vce/Documents/Common%20Weeds.pdf
Native Plant Finder (By Zip Code, ranked by the number of butterfly and moth species that use them as host plants for their caterpillars), https://www.nwf.org/nativePlantFinder/plants
“A Year of New-Home Landscaping and What I’ve Learned,” The Garden Shed (March, 2021), https://piedmontmastergardeners.org/article/a-year-of-new-home-landscaping-and-what-ive-learned/
“Be Wise When You Fertilize,” Clemson Cooperative Extension, https://www.clemson.edu/extension/carolinayards/yard-actions/be-wise-fertilize.html
“A Fertilization Primer: Plant Needs, Fertilizer Choices and Application Tips,” The Garden Shed (April, 2021), https://piedmontmastergardeners.org/article/a-fertilization-primer-plant-needs-fertilizer-choices-and-application-tips/
“Alert: Act Now – Pull Out Invasive Seedlings,” Blue Ridge PRISM (Partnership for Regional Invasive Species Management, 4/24/20 https://mailchi.mp/blueridgeprism/pullthoseseedlings?e=[UNIQID]
“Ticks and Tick-borne Diseases of Virginia,” Virginia Department of Health, https://www.vdh.virginia.gov/content/uploads/sites/12/2019/08/Tick-borne-Disease-in-Virginia-Flyer-8.5-x-11-format-for-website-.pdf
“Managing the Tick Problem,” The Garden Shed, (March, 2019), https://piedmontmastergardeners.org/article/managing-the-tick-problem/