Fall garden care tips: Improving soil, aerating lawns, planting bulbs
Plants like rhododendrons and azaleas that prefer acidic soil conditions can benefit from an application of granular sulfur to the soil in fall. Using sulfur is the best way to reduce the soil pH. Ideally, select plants that are suited for the existing pH in your soil. If your blue hydrangeas have turned pink, sulfur applications may return the flower color to blue.
Avoid contact with the sulfur by wearing latex gloves and keeping dust out of your eyes. Apply to the soil and gently scratch in. Sulfur works slowly in the soil and repeated applications may be necessary from year to year.
Autumn is a good time to core aerate your 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 with normal use. Very highly used lawns will benefit from being aerated twice a year. Core aeration 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 but not soaking wet. 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.
Allium or ornamental onions are some of the best bulbs for resistance to animal browsing. They come in many varieties. Try the popular June-blooming ‘Globemaster’, which features 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 that are about 1 inch wide. Lily leek (Allium moly), is a small species that is 10 to 14 inches tall with yellow flowers. These are just a few of the many alliums that succeed 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 animal favorites.
Continue to harvest vegetables as they ripen. Warm-season crops like peppers and tomatoes should be picked as soon as possible. Full-size 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 in 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 remain in the ground until after the first frost. 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.
Divide perennials that bloomed in spring and summer as needed. It is best to do this work soon so that 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.