How to tend your garden as autumn creeps in
Continue to harvest vegetables as they ripen. Warm-season crops such as peppers and tomatoes should be picked as soon as possible. Full-sized pumpkins need to remain on the vine as long as possible to achieve their maximum size. Continue to snip herbs to use fresh, to dry, or to freeze. Try making some extra pesto and freezing it an ice cube tray. Pop out the cubes when frozen and store in a plastic bag for use this winter. Collards, kale and Brussels sprouts will have improved taste if they are allowed to be hit with frost before harvesting. Maintain good sanitation throughout the vegetable garden. Remove diseased plants immediately, as well as those that have finished their growth cycle for the year. It is best to compost only healthy plant material.
• Before treating your plants with an insecticide, it is important to identify the insect to determine if the insect really is the problem. If it is, then you need to assess whether the damage being done warrants control, especially this late in the gardening season. The presence of insects feeding on the plants should not mean automatic treatment. Some insects are beneficial and help control other insects naturally. If an identified pest is causing significant damage, it is important to use a correct control measure along with proper timing. When choosing treatments, use the least toxic control possible.
• Autumn is a good time to core aerate the lawn to relieve soil compaction and reduce thatch, if you did not aerate in spring. Core aerating once a year is enough for most residential lawns; lawns with lots of traffic will benefit from being aerated twice a year. Core aerating also provides an opportunity for over-seeding 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.
• It's also time to think spring. Allium, or ornamental onions, are some of the best for resistance to animal browsing and come in many varieties. Try the popular June-blooming Globemaster with a 10-inch, pinkish-purple flower on a 2- to 3-foot stem; it lasts up to a month. The drumstick onion, Allium sphaerocephalon, has reliable burgundy blossoms about 1-inch wide. Allium moly, lily leek is 10 to 14 inches tall with yellow flowers. These are just a few of the many alliums that will grow well with little effort in Midwest gardens if planted this fall. Daffodils are also easy to grow and are resistant to animal browsing while tulips and crocuses are readily eaten.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.