Back Yard Bedtime

By Jeff Gillman, Special to Star Tribune

September 10, 2008

Fall is when the garden starts to wind down. It's also when we tend to forget that we have gardens. But we can't afford to turn our backs on our flowers, grass and trees now. Winter is on its way, and if we don't properly prepare our plants, they can end up with frozen roots or sun scald. Here's how to help your plants get set for winter.

Water

One of the best things you can do for your plants in fall is to water them. Once the ground freezes, plants have a difficult time taking up water, so they need a good dose of water before winter sets in.

If we continue to have dry weather, make sure to water once or twice a week through the fall. And remember, watering is especially important for young and newly planted trees and shrubs.

Lawn care

If you fertilize your grass only once a year, fall is the time to do it. Likewise, if you're planning on reseeding thin areas of your lawn, you should do it as soon as possible. (The best time to seed typically is mid-August to mid-September, but for the past few years, warmer-than-normal autumns have allowed us to seed a little later than usual.)

Just don't fertilize and plant grass seed at the same time. Because fertilizer can damage young roots, wait at least two weeks after fertilizing to seed.

Mulch perennials

For tender perennials such as butterfly bush and other plants that are marginally hardy here, you can start to put down a layer of mulch during the next few weeks. Mulch will help insulate the roots, protecting them from the bitter cold that invariably comes our way. You can wait until the first hard frosts to mulch hardy perennials.

Straw and hay are great for mulch because their hollow stems hold an insulating layer of air. Dry leaves also work well. Spread at least 6 inches of mulch over your perennial and bulb beds.

Take care of trees

Our dry summer may have left some trees heading into fall stressed by drought. So make sure your trees are well-watered throughout fall. Unless we get rain, water well once a week until the trees lose their leaves. (After that, deciduous trees lose some of their ability to take up water.)

A layer of mulch spread around the base will offer all the protection most established, large trees (more than 8 inches in diameter) need.

However, smaller trees and those with thin bark can benefit from tree wraps. Tree wraps made from thick brown paper are the most common. Unfortunately, they're also the least likely to provide any protection. A better choice would be the white spiral plastic wraps. They work well against critters and do a good job of protecting tree trunks from sun scald, where the sun heats the bark of a tree during the winter and injures it. If you use a wrap, be sure to remove it at the end of winter.

Early fall is a good time to plant trees. In addition, if you buy trees in fall, you may be able to take advantage of discounts at garden centers.

One note of caution: There are a few tree species that don't handle fall planting as well as others. Oaks, birches, hawthorns and fruit trees prefer to be planted in the spring. If you do decide to plant one of these species, make sure you select container-grown trees or balled-and-burlapped trees that were harvested this spring. They're more likely to thrive than trees that have been recently harvested.

While it's possible to plant trees right up until the first frost, it's wise to plant before temperatures drop into the 30s. That will give the roots a little time to develop.

Jeff Gillman is an associate professor of horticulture at the University of Minnesota. He's also the author of two books, "The Truth About Garden Remedies" and "The Truth About Organic Gardening" (Timber Press, $12.95).