Keep deadheading

Continue to deadhead annuals to encourage additional flowers and to keep the plants looking tidy.

Leave perennials standing

Remove spent blooms on perennials but do not cut them back until their leaves and stems have lost all green color.

Plant asters and mums

Asters (Aster spp.) and mums (Chrysanthemum spp.) purchased in bloom this month are usually greenhouse-grown and not necessarily hardy. Plant early in the month in garden beds to increase their chances of making it through the winter. This should give plants four to six weeks to establish their roots before the Chicago area’s first frost. Water well after planting.

Divide peonies

Peonies (Paeonia spp.) can be divided and planted early this month, to help their root systems become established before winter.

• Peony plants prefer a full sun location with well-drained soil.
• Water transplants well to encourage healthy root development.
• Peonies should be planted so that the buds or eyes are approximately 1 inch below soil level. If planted too deeply, they will fail to flower.

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Keep up with the fall harvest

It’s important to continue picking vegetables as they ripen. Remove diseased plants immediately, as well as those that have finished their growth cycle for the year. Compost only healthy plant material.

• Warm-season crops, such as peppers and tomatoes, must be picked as soon as possible.
• If an early frost threatens, cover warm-season crops with baskets or light blankets.
• Tomatoes are best stored at room temperature for short periods of time. Refrigeration may cause them to lose their flavor.
• Begin to harvest late-season squash and early pumpkins when the vines begin to wither.
• Full-sized pumpkins need to remain on the vine as long as possible to achieve their maximum size.
• Allow Brussels sprouts, collards, and kale to be hit with frost before harvesting. This improves their flavor.
• Begin to harvest any cool-season chard, lettuces, peas, radishes, or spinach planted in August.
• Continue to harvest herbs by snipping foliage. Pinch off developing flowers to retain essential oils and flavor in the plants’ foliage.
• To preserve herbs for winter cooking, dry entire sprigs or plants, or freeze individual portions in ice-cube trays.
• If herbs have gone to flower or seed, discontinue harvesting, since the flavor will have left the foliage. However, consider letting some plants remain in the garden; pollinators will appreciate their flowers.

Tend to raspberry bushes

Ever-bearing raspberry bushes will produce their fall crop on the top half of the canes. After harvest, prune out the top half of the plants. The lower half of the canes will produce fruit early next summer. After harvesting the summer crop, prune the canes to the ground.

Seed the lawn

Early this month, entire lawns or bare patches may be seeded with an appropriate grass seed mix.

Address grub damage

Grubs, which chew grass roots, may be present if your turf begins to brown and lifts easily off the ground. Minor damage is usually not cause for treatment.

• Pull back turf and check for white, C-shaped larvae with black heads. If more than 10 to 12 grubs are present in a square foot of soil, treatment is advised. Chemical controls vary in their timing.
• Homeowners can spot-treat small areas immediately with a recommended control or wait until late June to apply a preventative grub control. Keep in mind that as temperatures become progressively cooler in fall, grubs will move farther down in the soil, making them out of reach of chemical treatments.

Aerate the lawn

Consider core-aeration, which removes plugs of soil and grass at regular intervals throughout the lawn. Aerating helps rectify compacted soil, reduces heavy thatch accumulation, and may improve drainage. Professional lawn services can provide the service or equipment can be rented.

• Plugs can be left on lawns to break down.
• Avoid aerating the lawn when the soil is extremely wet.

Time to fertilize

September’s typically moderate temperatures, cooler nights, and adequate rainfall can spur grass growth, making mid-month a good time to feed turf with a fertilizer. Choose a product formulated for turf.

Plant trees and shrubs

Many trees and shrubs can be successfully planted in the fall, when moderate daytime and cooler night temperatures are ideal for planting. The warm soil and the return of autumnal rains provide good conditions for woody plants to establish their root systems before going dormant.

• Wait until trees and shrubs drop their leaves or undergo color change before planting them or digging and moving them to new sites. At that time, they are entering dormancy and will not suffer as much transplant shock.
• Broadleaved and needled evergreens, both dwarf and standard, are best planted or moved early in the month.

• Water deeply and thoroughly at planting time and once a week until the ground freezes.

Keep watering

Continue to water large trees and shrubs, especially evergreens, as well as plants that are 1 or 2 years old, until the ground freezes hard. Evergreens will continue to lose moisture through their needles throughout the winter and need adequate water in their root zones to avoid winter burn or desiccated needles.

Postpone fertilizing

Wait until October to fertilize any tree or shrub that looks like it might benefit from extra nutrition—signs include stunted growth, failure to fully flower or leaf out, undersized fruit, and/or off-color foliage. Avoid fertilizing newly planted trees until they are fully established, which may take a few years.