Fall preparations can protect trees from deer damage

It is time to protect the trunks of smooth-barked trees, such as young maples, from deer rubs. Deer rub their antlers on the trunks of smooth-barked trees to accelerate the removal of velvet from the antlers, as well as to mark territory, work off aggression and intimidate other bucks during the mating season.

This rubbing can damage the bark and even kill trees if the damage goes all around the trunk. Wrap the trunks with hardware cloth fencing, chicken wire or plastic snow fencing to a height of 5 feet to help protect the tree. This protection can be removed in early spring.

• Crabgrass may be evident in your lawn now, especially if it has been neglected. This annual weedy grass seeds readily in the fall. Pull it out by hand if the infestation is small to prevent it from setting seed.

Crabgrass will set seed at ground level, so it is not feasible to mow it low to prevent seed formation. There are herbicides that will control crabgrass, but they are not as effective this late in the season.

Make note of bad areas in your lawn and apply a pre-emergent herbicide (one that prevents weed seeds from germinating) in early spring before lilacs flower.

• Powdery mildew (a disease that causes a grayish, powdery film on leaves) is present now. Common plants that get powdery mildew include lilacs, phlox, bee balm, zinnias and nannyberry viburnum.

This disease typically occurs in the late summer when the weather is warm and humid. Fungicides can help control powdery mildew if applied before the infection becomes severe. MilStop is an organic control for powdery mildew.

In most cases, there is no need to apply any controls for powdery mildew at this time of year. Other options include selecting more mildew-resistant varieties, or moving the infected plants to an area of the garden that has better air circulation.

• Fertilize your lawn in early September to improve the color and vigor of the grass. Nitrogen is the most essential nutrient, although too much nitrogen can cause excessive top growth and disease problems. In most cases, a rate of one pound of nitrogen per 1000 square feet of lawn is adequate.

Many soils in the Chicago area have adequate levels of phosphorus, so it is likely not needed for your lawn. Some villages ban the use of phosphorus to improve water quality, as it can fuel algae growth in lakes and streams. If you only fertilize your lawn once a year, this is the best time to fertilize it.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.