Ornamental Horticulture (OH) Leaflet 37
Although most perennials are through bloom by fall, and some gardeners are ready to throw in the towel, attention to the following 10 tips will help ensure your perennials survive winter and that you'll have an even better perennial garden next spring. All these were learned through personal experience, and serve as my own checklist each fall.
1. Make "action" notes. Before you forget what should be divided, what should be moved and where, what you need to do to certain plants next year, write it down now.
2. Should perennials be cut back now? It depends. If you normally get little snow, you may want to leave them until spring so the stems can trap the snow. If you have perennials with attractive winter interest such as Sedum 'Autumn Joy' or ornamental grasses, you may wish to leave them for winter effect. Some seedheads such as black-eyed susan may provide food for birds. On the other hand, if you have rodents such as mice you may want to cut back ornamental grasses as they provide a winter home. Or if your perennials are diseased, you may wish to cut them back and destroy--don't compost-- the diseased stems and leaves. Often gardeners in cold climates with short seasons have more time for cutting back in the fall than spring. When cutting back leave a couple inches of stems to help trap the snow.
3. Check labels. As a famous garden writer once said, the only thing worse than a plant without a label is a label without a plant. What I've found best so far are the soft aluminum labels you write on and make an impression. Even if the ink goes, the impression remains to identify the plant. Or plastic labels, replaced yearly or as they become brittle, with just a plain pencil work well. So if you want to keep track of your perennials, check their labels now. If you are cutting back perennials, then is a good time to check their labels while you can still tell what a plant is. If you have a bed of many cultivars of the same type perennial, a map is a good idea in case labels get lost or moved. Take inventory of what you have. This is quite helpful when looking through winter catalogs and shopping next spring to avoid buying duplicates.
4. Cover or mulch. This in part depends on your philosophy. Mine is that perennials should be able to survive with their summer mulch-- a couple inches of bark mulch, shredded leaves or similar-- or else placed in a warmer microclimate site, pots to winter indoors, or not grown. Others don't feel this way, or have special perennials, in which case more winter mulch is needed. A foot or more of loose organic materials such as straw can be used. Don't use hay as it often has weed seeds. And don't use such mulch if you have rodents, as this only provides them a home and your perennials their winter food. Apply mulches late, such as mid-November, as perennials need some cold to harden properly. And remove mulches as early as possible or when snow goes, at least by April 1 during a period of several warm days. Leaving mulch on too long will lead to tender and weak growth as perennials grow under the mulch. If your perennials aren't mulched at all, on bare ground, you may want to provide a light layer of a couple inches of mulch as mentioned above. This will provide 5 to 10 degrees of temperature protection to the soil, which may mean life or death for certain perennials. And even a light layer of mulch helps prevent wide temperature fluctuations and freezing and thawing which breaks roots. Such organic mulches of course will break down, adding vital organic matter to the soil, and help conserve moisture and prevent so many weeds during the growing season.
5. Think like a rodent. As already mentioned, several practices such as cutting back and mulching can attract or deter rodents such as voles and mice. If you have such pests, one option is to have dogs or cats. Another is to get traps. Spring traps work on either, the live traps such as "have a heart" work on mice, chipmunks and squirrels only as voles usually live in the ground. For voles, an effective trap is to bait an inexpensive spring trap with peanut butter, placing it by an entry hole to their burrow, and then placing a pot over hole and trap. This way they think they're still in the burrow and come for the bait. Sound devices which emit music or frequencies haven't worked in my beds. When planting bulbs, avoid odorful organic materials such as bone meal which attract small animals. Instead use rock phosphate or superphosphate. Avoid poison baits if you have pets or children, or poisoned animals might be eaten by other animals. Since perennials die back to the ground, winter damage from deer usually isn't a problem.
6. Fall fertility. Roots grow until ground temperatures are about 40 degrees-- about the first of November. Putting synthetic fertilizer, which is quicker acting than organic, on at least a month before this may help. The best practice is to do a soil test in fall, especially if you haven't for a couple years, and lime if needed. Lime is slow acting, and will have changed the soil pH by spring when plants begin growing and needing nutrients. Compost can be added in fall, especially if you cut back perennials. Otherwise if your beds are full, it may be hard to get around all the plants. Fall compost application saves one less chore from spring. Although compost will add some nutrients, it has so many other beneficial effects such as on soil organic matter and microorganisms that fall application can be useful.
7. Make new beds. If you want new perennial beds by spring, now is a good time to start. If in hay, cut back low in the fall. For sodded areas, these can be stripped of sod with a rented sod cutter. Or you can use a herbicide to kill the grass. Or you can just cover with black plastic, and most of the grass will be dead and composted by spring, and fairly easy to plant. Soil test and add lime now if needed.
8. Cage your tall perennials. If you have tall perennials, an effective method of staking is to make a cage of wide mesh fence or concrete reinforcing wire (call a concrete company for this) and place around them. During the slower fall months when you're not busy mowing and weeding, make up some of these and place on taller plants once cut back. If in a windy area, you may also have to put in a stake with the cage to hold it in place. You may have a couple heights for different height perennials. Plants will then grow up through the cage next spring, often hiding it entirely.
9. Roses. Many gardeners have questions on overwintering these, and should consult the separate leaflet on this subject. Some tips though include making sure grafted roses have the graft union below ground a couple inches or covered with soil; mulch with only soil or styrofoam cones if you have rodents, not with straw; cut back only to top of mulch. There are many hardy shrub roses, both new and old varieties, which require little or no protection.
10. Bulbs. Dig and store in a cool but non-freezing place such tender summer bulbs as gladiolus, caladiums, cannas, crocosmias, dahlias and tuberoses. Plant spring bulbs such as daffodils, tulips and crocus before November in order to allow time to get established. Do not plant too early, such as late August, or they may start growing above ground. And if you have rodents and similar pests avoid tulips which they love, or plant with ground oyster shells which they supposedly hate.
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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. Lawrence Forcier, Director, UVM Extension System, Burlington, Vermont. University of Vermont Extension System and U.S. Department of Agriculture cooperating, offer education and employment to everyone, without regard to race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status.
Last reviewed 11/07/96