Fall is a good time to feed, aerate your lawn
Fertilize your lawn in early September to improve the color and vigor of the grass. Nitrogen is the nutrient required the most, although too much nitrogen can cause excessive top growth and disease problems. A rate of one pound of nitrogen per 1,000 square feet of lawn is adequate for most lawns.
Many soils in the Chicago region have adequate levels of phosphorus, so it is likely not needed for your lawn. Fertilizer bags have three numbers. These represent the percentages of nitrogen, phosphorus and potassium. The middle number is phosphorus.
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.
Let your lawn breathe
Autumn is a good time to core aerate your lawn to reduce soil compaction and thatch if you did not aerate in spring.
Core aerating once a year is enough for most residential lawns with normal use. Very high-use lawns will benefit from being aerated twice a year. It also provides an opportunity for overseeding to help improve and thicken up your lawn. Keep the seed moist for good germination.
Core aerating is best done when the ground is somewhat moist. Leave the soil/grass plugs on the lawn to break up and filter back down to the soil level. The plugs typically break down in seven to 14 days. Mark sprinkler heads and light fixtures in the lawn so they will not be damaged.
Deer can damage tree trunks
It is time to protect the trunks of smooth-barked trees like young maples from deer rubs if you have deer active in your neighborhood. Deer rub their antlers on trees, typically using the trunks of smooth-barked trees. This can damage the bark and even kill trees if the damage goes all around the trunk. Wrap the trunks with hardware cloth, chicken wire or plastic snow fencing to a height of 5 feet to help protect the tree.
Paper tree wrap does not provide enough protection against a determined deer. This protection can be removed in late winter or early spring.
Divide to multiply blooms
Divide perennials that bloomed in spring and summer as needed. It is best to do this work early in the month so the plants have time to establish before winter sets in. Mulch the newly planted divisions.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.