The Ornamental Garden in October
In October, the ornamental garden offers up a riot of color that is unrivaled by any other season. Most fall-blooming species are at their peak this month. Autumn foliage adds saturated shades of red, gold, purple, and orange to the mix. As if that weren’t glorious enough, in late afternoon, the shifting angle of the sun lends a golden veneer to the entire landscape.
WHAT’S IN BLOOM IN OCTOBER?
October has a broad palette of plants to choose from – abelia, agastache, globe amaranth, lantana, roses, sedum, salvia, zinnias, and grasses, just to name a few. The real stars of the show are tried and true fall-blooming plants such as:
- Aster – Regardless of which species you grow (New England, New York, aromatic, smooth, wood, etc.), asters provide masses of blooms and gorgeous color in the sunny border. One of the best of the bunch is ‘Raydon’s Favorite’ (Symphyotrichum oblongifolium), a marvelous lavender-blue selection recognized by The Garden Club of America as its 2016 Plant of the Year.
- Hydrangea – Many hydrangea species and hybrids provide multiple seasons of color. For example, ‘Limelight’ (Hydrangea paniculata) blossoms gradually fade from pale greenish white in summer to a luscious shade of deep pink in autumn. ‘Endless Summer’ (Hydrangea macrophylla) turns from either pink or blue to a deep rose, arguably prettier than the summer colors.
- Tall Sedum
From the moment the foliage emerges in spring until frost covers its seed heads in winter, this hardy, drought-tolerant plant looks great all year round. Depending on the selection, fall blossoms range in color from soft pink to deep brick red. ‘Autumn Joy’ is the best known of the tall sedums, but ‘Autumn Fire’, ‘Matrona’, and ‘Neon’ are other selections that are easy to find.
- Chrysanthemum – Hardy garden mums provide a looser, less formal look than the tightly formed, spherical cushion mums that flood garden centers in autumn.
Generally ranging in height from two to three feet, hardy mums bloom non-stop until the first killing frost. ‘Sheffield’ is a particularly lovely selection with deep salmon pink buds that fade to soft apricot flowers. ‘Cambodian Queen’ makes a huge impact with masses of clear orchid-pink flowers.
- Pink Muhly Grass (Muhlenbergia capillaris) – This native plant transforms from a simple clump-forming grass to a billowy haze of deep mauve in autumn. Spectacular when back-lit by sunlight, muhly grass is easy to grow and undemanding.
GENERAL FALL CLEANUP AND GARDEN MAINTENANCE TASKS
Most of the chores on your September to-do list still apply in October – weeding, deadheading, transplanting, planting new trees and shrubs, taking cuttings, and more. Only now, there’s a greater sense of urgency as the weather starts to turn chilly.
- Continue to tidy up flowerbeds. Bag and dispose of any diseased plant materials. Rake dead leaves from beneath rose bushes and other plants that may have developed black spot or other fungal diseases over the summer. If left to overwinter on decaying leaves, these fungal spores will affect next year’s garden.
- Shred or chop fallen leaves and compost them or save them to use as mulch on next year’s garden. If you’re new to composting, check out Virginia Cooperative Extension (VCE) Publication 426-703, “Making Compost from Yard Waste” (pubs.ext.vt.edu/426/426-703).
- Remove cool-season weeds, such as chickweed, dandelion, wild onion, plantain and white clover. A few minutes spent pulling these weeds from flowerbeds now will save you many hours of work next spring.
- Have a soil test done this fall if you haven’t had one done in the past two or three years. Soil amendments, such as lime, manure, compost and chopped leaves, are best added to flower beds in the fall. But don’t amend until after you get the results of the soil test. For additional information on soil testing, see VCE Publication 452-129, “Soil Sampling for the Home Gardener” (pubs.ext.vt.edu/452/452-129).
- Hold off on mulching flowerbeds until after the soil freezes. That may not be until November or December. Just keep in mind that mulch applied to warm soil in fall can do more harm than good. The purpose of mulch is not to keep the soil warm but to help keep the soil temperature constant and to help prevent frost heaving.
- As you perform your fall cleanup chores, look for interesting dried plant materials that you can use for winter arrangements and crafts. Look for dried milkweed pods, sweet gum seed pods, dried flowers, locust pods, staghorn sumac, various grasses and grains, lichens, and mosses.
ANNUALS AND PERENNIALS
Watch the weather for the first killing frost. The days are now noticeably shorter, so stay alert to night-time temperatures.
- If chilly overnight temperatures are predicted, cover fall-flowering perennials such as mums and asters to prevent frost from cutting short the blooming period. Just remember to remove the cover if warm temperatures are expected for the next day.
- Cut back perennial foliage after a killing frost, leaving some seed heads to provide food for wildlife. During the winter, when food is scarce, seed-eating birds, such as finches, sparrows, chickadees and nuthatchs, appreciate the seed heads of Echinacea, Rudbeckia, Helianthus, coreopsis, lavender, Russian sage, teasel, thistles, grasses, and grains.
- If you haven’t gotten around to saving seeds from annuals to use in next year’s garden, do it now. As a reminder, seeds from hybrids are unlikely to come true.
- Leave seed heads in place for annuals that you want to self-seed or just scatter the mature seeds where you want them yourself. Some annuals and biennials that reseed themselves include cleome, cockscomb, cosmos, foxglove, hollyhock, larkspur, money plant, sweet William, forget-me-not, Shirley poppy, zinnia, four-o-clock, marigold, vinca, and impatiens.
- Pull out spent annuals. Compost them if they are disease and pest free or, if not, bag them and put them in the trash if they are not.
- It’s not too late to plant cool-season annuals such as snapdragons, larkspur, pansies, violas, calendula, Iceland poppies, California poppies, or love-in-a-mist.
- Divide and transplant spring and summer-blooming perennials early in October. Most perennials, including daylilies, coreopsis, Shasta daisy, lamb’s ears, penstemon, and yarrow, benefit from being divided every three to five years. If you’re not sure whether a plant needs dividing, step back and take a look at it with a critical eye. Does the plant splay open or split in the middle? Does the center of the plant have smaller leaves or fewer flowers? Does the center of the plant appear to be dead? Does the plant appear to be crowding its neighbor plants? If the answer to any of these questions is yes, then the plant needs to be divided. Early fall is an ideal time to divide plants because they will have time to establish new roots over winter and will be better equipped to deal with next summer’s heat and dry weather.
- Take cuttings to root over the winter. If you’re not sure how to do this, see VCE Publication 426-002, “Propagation by Cuttings, Layering and Division” (pubs.ext.vt.edu/426/426-002).
TREES AND SHRUBS
Fall is the ideal time to plant trees and shrubs in your landscape. Think about selecting plants that offer multi-seasonal interest. Some trees to consider include maple (Acer spp.), ginko, black gum (Nyssa sylvatica), dogwood (Cornus), or sourwood (Oxydendrum arboretum). Some suggested shrubs for multi-seasonal interest include Virginia sweetspire (Itea virginica), oakleaf hydrangea (Hydrangea quercifolia), fothergilla (Fothergilla gardenii), blueberry (vaccinium spp.), red-twig dogwood (Cornus spp.), or spicebush (lindera benzoin).
- Take preemptive action to prevent deer damage to the bark or branches of young or newly planted trees and shrubs. In fall and winter, male deer rub or scrape against young trees for two reasons: (1) to rub the summer velvet from their horns and (2) to mark their territory as a way to attract female deer and warn other male deer away. Wrap vulnerable tree trunks with a physical barrier such as wire or plastic mesh tree guards, chicken wire, or woven wire fencing. This will protect the trees while allowing them room to grow.
- Water newly planted trees and shrubs until the ground freezes. This is critical to the survival of the plants over the winter months.
- Inspect your evergreen trees and shrubs for bagworms. Bagworm eggs overwinter on evergreens such as junipers, spruce, hemlock, and arborvitae as well as many other trees. Pick off and burn any egg cases that you find. See VCE Publication ENTO-83NP, “Bagworm” (pubs.ext.vt.edu/2808/2808-1008).
- While conifers such as spruces, firs, and pines routinely shed their oldest needles in fall, yellowing needles on this year’s growth may indicate drought stress or possibly disease or insect damage. If concerned about the health of the tree, contact the Virginia Cooperative Extension helpdesk (434-872-4583 or email@example.com) for advice.
- Divide and transplant Asiatic and oriental lilies early in the month. If not divided every two or three years, they lose their vigor and either stop blooming or produce smaller flowers.
Carefully dig about one foot down and several inches out from the plants so that you don’t damage the bulbs with your spade. Lift the bulbs from the soil and gently separate the attached bulblets from each “mother” bulb. Do not let the bulbs dry out. Replant them immediately in groups of three or more spaced about 8 to 10 inches apart. Plant the original bulbs about five or six inches deep and the bulblets about three or four inches deep.
- Dig up tender bulbs, such as caladiums and dahlias, after the first frost blackens the foliage. Allow them to dry off and gently brush any loose dirt and debris from them. Store in a cool, frost-free location over the winter months.
- Plant spring-blooming bulbs, now that soil temperatures are dropping into the 60s or below. Plant a selection of bulbs for a succession of color next year starting with the earliest snowdrops and ending with the latest blooming tulips. As you plant bulbs, loosen the soil with a trowel or a bulb planter and place the bulb with the root side down. If you’re not sure which is the root side versus the blooming end, just plant the bulb on its side. The bulb will figure it out for you.
- As a precaution, wear gloves when handling bulbs or wash your hands with cool water and soap immediately after planting. Some people have a reaction similar to contact dermatitis when handling tulip, daffodil or hyacinth bulbs. For people who are susceptible, the bulbs may irritate the skin causing a rash, itching, inflammation, and blisters.
Now that houseplants have been moved back indoors, pay attention to their needs so that they stay healthy and look their best over the winter months.
- The best way to kill a houseplant is to overwater it. To avoid this, allow potting soil to dry between waterings. As the days grow shorter and light intensity is reduced, houseplants need less water.
- Another mistake is to plant a houseplant in a pot that doesn’t have a drainage hole. Water collects in the bottom of the pot and can cause roots to rot. Always check houseplants to make sure water drains away from the roots.
- Water houseplants with room-temperature water. Tropical plants in particular do not like water below 65°F. Cold water may reduce leaf size, cause leaf drop, and may possibly kill the plant. Warmer water actually stimulates growth.
If you have an amaryllis, Christmas cactus, kalanchoe, or poinsettia, start conditioning it now for re-bloom during the winter holidays. These are photoperiodic plants, which 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.
- Amaryllis (Hippeastrum) bulbs will re-bloom provided they go through a period of dormancy first. If you had an amaryllis bulb outside over the summer, bring it indoors by the first week of October. Amaryllis prefers to be pot bound, so leave it in its pot or, if the plant was growing in the ground, re-pot it in a pot that is just slightly larger than the bulb. Cut off any dead leaves at the top of the bulb but leave any live leaves alone. Place the potted plant in a dark, dry place for six to eight weeks. Do not water the bulb until the end of the dormant period. Once new growth appears, begin to water the bulb on a regular schedule.
- Christmas Cactus (Schlumbergera bridgesii) is one of the most popular houseplants over the holidays. If you have one and want it to re-bloom by the holidays, start conditioning it eight weeks in advance.
To set flower buds, they need 13 hours per day of uninterrupted total darkness at temperatures between 55 and 70°F. If you’re not able to provide overnight temperatures that cool, give the plant 15 hours of darkness at temperatures above 70 degrees. When the flower buds appear, increase the amount of water you give the plant but don’t overwater. Too much water may cause the buds to drop off.
- Kalanchoe (Kalanchoe blossfeldiana) should be kept in the dark for 13 hours per day for 30 days. After that, it should start to show flower buds. At that point, return the plant to normal periods of light and dark.
If this is too much trouble, the plant will bloom next spring under normal growing conditions. Should the plant become leggy and less vigorous-looking after it finishes blooming, cut it back and feed it with a water-soluble liquid fertilizer. Putting it outside next summer and giving it some sunlight will restore it to a robust, sturdy-looking plant.
- Poinsettias (Euphorbia pulcherrima) begin to develop flower buds in October in response to shorter days. However, to get the plant to re-bloom successfully, place it in a room or closet where night temperatures are around 60°F and protect it from artificial light at night for a minimum of 12 hours of darkness. Return it to a sunny window during the day. Start the darkness treatment about 11 weeks before Christmas and continue through the end of November, at which point the plant may be placed in a warm (60°F or warmer), sunny window. Provide adequate water and fertilizer throughout this time so that the plant produces a healthy display of color for the holidays.