The October To-Do List
Spring seems a short time ago on the one hand, and eons ago on the other. Spring gardens cheered us up and gave us something productive to do. Summer gardens continued to keep us busy, although a temperature record of 35 straight days over 90⁰ F shortened the working hours to early morning. Now it’s time for ornamental gardeners to start tidying up. Let’s look at the long list of tasks that we should tackle this month. But smile–it’s great to be outside in October!
A few tasks depend on first frost/freeze temperatures. According to National Climatic Data Center for the Albemarle County station, the projected first frost/freeze dates are shown below:
According to Virginia Cooperative Extension, the first projected frost for USDA Hardiness Zone 7a based on past averages is October 15-25. This range of first frost dates is a little less risky than the guideline for the first frost date given in the above chart. This highlights the different ways of interpreting this chart based on what you consider “risky.” If you’re willing to take a chance of earlier-than-expected frost, you’d move out to the right side of the chart. If you want to minimize damage from a first frost, you’d play it conservatively and move to the left. As an example, let’s say your garden is on the south side of the house, in a nice, protected warm spot. You can probably push the first frost date out a little further, perhaps to the end of October. If your garden is on an elevated spot and more open, you might want a more conservative date, and you could move closer to October 13.
Here’s a chart from the USDA National Water and Climate Center which summarizes the effects of cold temperatures on plants and vegetation:
- 32 to 29 degrees F is a light freeze: Tender plants killed, with little destructive effect on other vegetation.
- 28 to 25 degrees F is a moderate freeze: Widely destructive effect on most vegetation with heavy damage to fruit blossoms, tender and semi-hardy plants.
- 24 degrees F and less is a severe freeze: Heavy damage to most plants. At these temperatures, the ground freezes solid, with the depth of the frozen ground dependent on the duration and severity of the freeze, soil moisture, and soil type.
Now let’s look at specific October tasks, including some that will be be affected by temperature.
- Annuals: If you don’t like handling limp plants, remove tender annuals that die with the first frost, such as zinnias, plume celosia, impatiens, lantana, begonias, and coleus. Semi-hardy annuals such as petunia, pansy, and calendula can tolerate cool temperatures and a moderate frost (to about 28⁰ F).
Remember, soil doesn’t freeze as quickly as the air. Plant roots will still grow if soil temperature is above 40⁰ F. A “hard frost” or “killing frost” comes when the temperature drops further, below 28 degrees F, for about 5 hours. This will kill the top growth of most perennials.
- Perennials: Divide and transplant perennials. Recommendations differ regarding how late into the fall you can divide and transplant perennials. It would be nice to be able to say, “Transplant by X date,” but it’s not that clear cut. Most recommendations cite 4-6 weeks before the first freeze (24⁰ F) so that plants can set roots. This means that perennials should be divided starting in September and finished by about mid-October. This can also differ by hardiness of plants. More tender plants need a longer adjustment period.
- Cut back perennials, leaving some seed heads for self-seeding and for birds. Flowers such as coneflowers, rudbeckia, and agastache offer such seeds. See the October 2015 issue of The Garden Shed for a very helpful list of perennials that should not be cut back, and those that can be cut back.
- Ornamental grasses: Since many ornamental grasses are attractive in the garden during winter, cutting them back is usually done in late winter or early spring. Not cutting them in fall also helps protect the crown over winter.
- Spring-Flowering Bulbs: Continue to plant spring-flowering bulbs until the ground freezes. Bulbs do best if planted about one month before the first freeze. According to average data for our area, bulbs would best be planted up to November 1.
- Tender bulbs, including dahlia, canna lily, elephant ear (Colocasia), caladium, begonia (Begonia tuberosa), and gladiolus, are planted in the spring for summer bloom but cannot survive cold winter temperatures and must be dug up after the tops are browned each fall. Allow to dry, clean off soil, and store in peat moss or vermiculite in a cool location free from frost. Remember to label stored plant material carefully. The Missouri Botanical Garden is a good resource for highlighting requirements specific to different plants.
- Forcing Bulbs to Bloom Indoors: Depending on desired bloom time, pot up bulbs between September and December. A simplistic, but not guaranteed flowering schedule, is to plant in mid-September for late December flowers, mid-October for flowers in February, and mid-November for March/April flowers. In other words, expect about a three month wait period before a planted bulb blooms. For detailed instructions and a list of instructional videos, see the VCE publication, “Fooling Mother Nature: Forcing Flower Bulbs for Indoor Blooms.”
- Pruning: In general, DON’T PRUNE shrubs. According to the shrub pruning calendar published by Virginia Cooperative Extension, the only shrubs listed for pruning in October are potentilla and sumac. There are a few shrubs listed for November. Shrubs that bloom on new wood can be pruned in late winter. Shrubs that bloom on old wood can be pruned right after they bloom in spring or summer. Check the calendar if you have questions on particular shrubs.
- Cleaning Up Perennial Beds: Be sure to clean up from around your perennial flowers, particularly around plants that are prone to fungal infections, such as rose and peony. If left on the ground, leaves and stems can harbor diseases and provide convenient places for pests to spend the winter. Bag up diseased plant material and discard; don’t add it to the compost pile.
- Mark the Spot: As you clean out the flower beds, mark the spots where late-starting perennials will come up next spring. It’s also very helpful to mark the spots where you’ve planted bulbs.
- Plant Fall Seeds: According to the Clemson Cooperative Extension (USDA Hardiness Zone 8a), these are the hardy and semi-hardy annuals that can be planted as seed in the fall for spring bloom: Allysum (Lobularia maritima), Annual Phlox (Phlox drummondi), Cornflower (Centaurea cyanus), Foxglove (Digitalis purpurea ‘Foxy’), Larkspur (Consolida ambigua), Poppy (Papaver spp.), Pot Marigold (Calendula officinalis), Stocks (Matthiola incana), and Sweet Peas (Lathyrus odoratus). Check individual seed packets for information on fall planting in our zone, USDA Hardiness Zone 7a .
- Bring in Houseplants: Bring in houseplants when nighttime temperatures fall to 55⁰ F; wash off pots and hose off foliage or wipe with a wet cloth. Soak the pot in a tub of lukewarm water for about 15 minutes to force insects out of the soil. Check to see if roots are pushing through the bottom of the pot; if so, the plant needs to be repotted. If plants have gotten leggy over the summer, remove them from the container, and prune the top and roots in equal proportions. Replant in a cleaned pot with fresh potting soil (not garden soil).
- Help Houseplants Adjust: Plants will need to adjust to the lower indoor light level; be careful not to overwater. If plants are dropping leaves, they may not be getting enough light. Place them in a south-facing window, if possible, or at least in an east-facing window. Place pebble trays with water below plants that benefit from humidity.
- Start Plants from Cuttings: It’s a good time to take some cuttings from plants that have grown large over the summer. It’s also easier to store cuttings from larger annual plants, such as coleus or begonia, that you want to plant outside next spring. Either root the cuttings in water, or dip them in root hormone, and place in soil. For detailed guidance, read this month’s feature article Creating New Plants From Cuttings/Garden Shed Nov. 2020.
- Prepare Seasonal Indoor Bloomers: Start conditioning photoperiodic plants now for rebloom around the holidays. Photoperiodic means they react in a certain way to the daily cycles of daylight and darkness. By manipulating the amount of light they receive, you can control their bloom schedule. Such plants include: amaryllis, Christmas cactus, kalanchoe, and poinsettia. For specific instructions, refer to these articles in The Garden Shed, October 2016, or The Garden Shed, December 2019.
- Trees and shrubs: The best time to plant deciduous trees and shrubs in the fall is after the heat of summer diminishes, but before the ground has frozen. Mid-October through mid-November is a good planting guide in our area, although trees can be planted earlier in the fall as well. Newly installed woody plants do best when soil temperatures range from 55-75⁰ F. Root development typically stops when the soil temperature drops below 40⁰ F.
Deer Protection: Protect shrubs and young trees susceptible to deer damage.
- Leaves: Shred or chop fallen leaves and compost them or save them to use as mulch on next year’s garden.
The best time of year to fertilize a lawn depends on the type of grass in the lawn. If you have cool-season grasses (grow better in spring and fall), such as tall fescue, Kentucky bluegrass, and perennial rye-grass, it is best to fertilize in the late summer/early fall from August 15th through November. If you have warm-season grasses (grow better in summer), such as bermudagrass or zoysiagrass, fertilize from March to August. Never apply lawn fertilizer to frozen soils. Adding ¼ – ½” of compost as a “top dressing” provides organic matter and improves the overall health of the soil. A soil test is the only way to determine if the soil needs lime, phosphorus (P), or potassium (K) and fall is an excellent time to do a test. The soil-testing labs are usually less busy. Apply nutrients as recommended by a soil test and you’ll be taking a huge first step towards protecting water quality.
The one nutrient that won’t be analyzed in a soil test is nitrogen (N). The reason is that N levels change rapidly in a soil and test results usually have little meaning by the time you receive the report. The test results will provide recommendations on appropriate N application levels suitable for the grass and location.
Mow until the lawn stops growing. Grass that is too long is more susceptible to damage over the winter.
For information and how-to tips on lawn management, see the September 2020 Garden Shed article, “Responsible Lawn Management in the Era of Climate Change.”
One of the most important factors for the lawn is soil pH. This is a measurement of the acidity or alkalinity of the soil and is a major determining factor for proper nutrient absorption by turfgrass roots. In our area, the soil tends to naturally be more acid, meaning a pH of less than 7.0 and usually much lower, but a soil test is the only way to determine if the pH level needs to be shifted. The optimum pH for turf growth is 6.0 to 6.8. If the pH level falls below 5.5, turf growth will be compromised. Most vegetables, fruits, and ornamental plants grow best when the pH is slightly acidic, between 5.5 and 6.5. Multiple lime treatments may be required to bring the pH to the desired level. Fall and spring are generally the best times for lime applications. Fall has an added advantage, as rain, snow and cycles of freezing and thawing help lime break down and begin to work. For more information, read this article, “Does Your Lawn or Garden Need Lime?” from North Carolina Cooperative Extension.
Mulch is often applied in spring, but check on mulch levels in fall as well. Mulching helps prevent soil erosion; insulates the soil; retains water to keep roots moist; and prevents root heaving caused by freezing and thawing temperatures. Mulch boxwoods and broadleaf evergreens before the ground freezes. Mulch deciduous trees and shrubs, and perennial beds after the ground freezes, but before the coldest temperatures arrive. See the Charlottesville Area Tree Stewards guidelines for mulching around trees.
For more tips on what to do this month, see the Monthly Gardening Tips under Gardening Resources, piedmontmastergardeners.org/Monthly Gardening Tips#October. We also recommend reviewing “The Ornamental Garden in October,” from past issues of The Garden Shed: October 2015, October 2016, October 2017, October 2018, and October 2019.
“Lime and Lawns,” University of Maryland Extension, https://extension.umd.edu/hgic/topics/lime-and-lawns
“Does Your Lawn or Garden Need Lime?” NC Cooperative Extension, https://pender.ces.ncsu.edu/2020/03/does-your-lawn-or-garden-need-lime/
Active Weather Alert, NBC.com, https://www.nbc29.com/2020/07/31/active-weather-alert/
“A Guide to Successful Pruning, Shrub Pruning Calendar, Virginia Cooperative Extension, https://www.pubs.ext.vt.edu/430/430-462/430-462.html
Virginia’s Home Garden Vegetable Planting Guide: Recommended Planting Dates and Amounts to Plant, Virginia Cooperative Extension, https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-331/SPES-170.pdf
“WETS Tables Growing Season Dates and Length,” USDA National Water and Climate Center, https://www.wcc.nrcs.usda.gov/climate/wets_dates.html
“First and Last Frost/Freeze Dates by Zip code,” Dave’s Garden, https://davesgarden.com/guides/freeze-frost-dates/index.php?q=22901&submit=Go
“Dividing Perennials,” Clemson Cooperative Extension, https://hgic.clemson.edu/factsheet/dividing-perennials/
“October Tips,” Virginia Cooperative Extension, https://albemarle.ext.vt.edu/content/dam/albemarle_ext_vt_edu/files/hort-tip-sheets/10-14-perennials.pdf
“Growing Annuals,” Clemson Cooperative Extension, https://hgic.clemson.edu/factsheet/growing-annuals/
“Ornamental Grasses and Grass-like Plants,” Clemson Cooperative Extension, https://hgic.clemson.edu/factsheet/ornamental-grasses-and-grass-like-plants/
“Holiday Cactus Brings the Gift of Color,” The Garden Shed, https://piedmontmastergardeners.org/article/holiday-cactus-brings-the-gift-of-color/
“Making More: Propagation by Cuttings,” Clemson Cooperative Extension, https://hgic.clemson.edu/making-more-propagation-by-cuttings/
“Protecting Your Garden From Frost,” The Old Farmer’s Almanac, https://www.almanac.com/protecting-your-garden-frost
Feature photo: Pink Muhly and Little Bluestem Grasses Photo: Susan Martin