October garden tasks: Midwest

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Frost and freeze timing by zone

As the September guide notes, the Midwest's first-frost dates span about a month. Minneapolis–St. Paul averages its first frost around October 7, and per UMN Extension its first hard freeze (28°F) comes around October 14. Chicago averages around October 22, and Kansas City around November 1.

• Zones 3–4 (northern MN, WI, MI): October is the last month to plant. The vegetable garden is finished except for kale, Brussels sprouts, leeks and root crops.
• Zone 5 (Chicago, Milwaukee, Des Moines, Detroit, Columbus): frost arrives mid-month. Cold-tolerant greens keep going under row cover.
• Zone 6 (St. Louis, Kansas City, Indianapolis, Cincinnati): October is still a working garden month with fall crops in the ground.

At the first frost warning, pick all tomatoes and peppers. Green tomatoes ripen indoors. Cover lettuce and chard overnight. Kale, collards, spinach, carrots and parsnips handle light frost and often taste sweeter afterward. Harvest winter squash and pumpkins before a hard freeze and cure them in a warm room before storing.

Carrots, parsnips and leeks can stay in the ground under a thick layer of straw or shredded leaves and be dug through late fall in zones 5–6. Parsnips taste sweeter after cold weather. Once a vegetable bed is cleared, sow winter rye right away. It is the cover crop most likely to germinate in cool October soil, and it holds the bed through winter. See green manure cover crops. Bring houseplants that summered outdoors inside before nights fall into the 40s, and check them for insects first.

Plant garlic

Garlic is planted in fall for harvest the following summer. Per UMN Extension and Iowa State Extension, the goal is to plant early enough that cloves grow roots before the ground freezes, but late enough that they do not send up much top growth.

• Zones 3–4: early October.
• Zone 5: mid-to-late October.
• Zone 6: late October into early November.

Break bulbs into cloves just before planting and set the largest cloves pointed end up, about 2 inches deep and 4–6 inches apart, in loose, well-drained soil. Hardneck types are generally the more reliable choice for the coldest parts of the Midwest. Buy seed garlic from a regional grower rather than using grocery-store bulbs.

Once the soil begins to freeze, cover the bed with several inches of clean straw. UW–Madison Extension describes mulching as an important step in Wisconsin, where bare soil can freeze deeply and heave. Pull the straw back in spring once shoots appear.

Spring bulbs and tender bulbs

Plant spring bulbs once soil at 4 inches is below about 60°F. The September guide lays out the timing: zone 4 by mid-October, zone 5 through October, and zone 6 in October and November. Per Illinois Extension:

• Plant bulbs pointed end up, at a depth of about three times the bulb's height. Large tulips and daffodils go roughly 6–8 inches deep.
• Choose a sunny, well-drained spot. Bulbs rot in soggy clay, so amend heavy soil or plant on a slight rise.
• Water after planting so roots start before the ground freezes.
• Squirrels dig up tulips and crocus. Daffodils and alliums are left alone.

University of Missouri Extension notes that zone 6 gardeners can plant bulbs into November as long as the ground can be dug.

Dig tender bulbs after frost blackens the foliage. Per Michigan State University Extension, dig dahlias, cannas, gladiolus and tuberous begonias carefully, let them dry briefly out of the sun, remove loose soil, and store them in a cool, dark, frost-free place. Label each variety before you dig. See overwintering dahlias.

Lawn: keep mowing, feed late, mind the rules

September is the most important lawn month in the Midwest, and October follows through.

• Mowing: keep mowing at your normal height (about 3 inches for most cool-season lawns) as long as the grass grows. Purdue's turf program advises against dropping the mower height for the last cut. Scalping stresses the crowns going into winter.
• Late-season nitrogen: per Purdue, a fall nitrogen application when top growth slows but the grass is still green builds roots and carbohydrate reserves and gives earlier spring green-up without a flush of spring mowing. In zones 5–6 this usually falls in late October to November. In zones 3–4 it comes earlier, before the grass goes dormant. UMN Extension gives the same advice for Minnesota.
• State rules: Minnesota, Wisconsin and Illinois restrict phosphorus in lawn fertilizer unless a soil test shows a need. Wisconsin law also bars applying lawn fertilizer to frozen ground. Sweep granules off pavement.
• Perennial broadleaf weeds: fall, when dandelions and creeping Charlie move sugars down to their roots, is the most effective time to treat them if you use herbicides. Spot-treat and follow the label.

Leaves and selective cleanup

Mow leaves into the lawn. UMN Extension and Michigan State research both found that shredding fallen leaves into the lawn with a mower does not hurt turf, as long as grass is still visible afterward. It returns organic matter to the soil. Heavy oak and maple drifts can be shredded and used as mulch on vegetable and perennial beds, or composted. See building compost.

Clean up selectively. Illinois Extension recommends leaving some stems and leaf litter in place, because many native bees and other beneficial insects spend the winter in hollow stems and leaf litter.

• Remove and throw out diseased foliage and fruit: tomato vines with blight, peony leaves with botrytis, apple scab leaves and mummified fruit.
• Leave healthy perennials, seed heads and ornamental grasses standing until spring, as the September guide recommends.
• Cut hostas and other plants that collapse into mush after frost.

Trees, shrubs and soil tests

Plant trees and shrubs early in the month. Purdue Consumer Horticulture calls fall an ideal time to plant trees, because roots keep growing in warm soil after the air cools. In zones 3–4, finish by early October. Zones 5–6 can plant container-grown stock through October. Water deeply each week that rain falls short until the ground freezes. As the September guide notes, do not fertilize newly planted trees until spring.

Young-tree protection: in zones 3–5, thin-barked young trees such as maple, linden, crabapple and honeylocust should be wrapped before winter if you have not done it yet. Put hardware-cloth guards around fruit tree trunks against rabbits and voles. See winter tree wrap.

Soil test: fall sampling gets results back before spring and gives lime or sulfur time to work. A soil test is also what qualifies you to use phosphorus fertilizer in the states that restrict it. Take several cores per area, mix them, and send one composite sample per area to your state's Extension soil lab. Our soil testing guide covers the steps.

Common mistakes

Frequently asked

Is it too late to plant bulbs after the first frost?

No. Bulbs go in based on soil temperature, not air temperature, and the soil stays workable for weeks after the first frost. Plant until the ground freezes: mid-October in zone 4, late October to early November in zones 5–6.

Should I rake leaves or leave them?

Mow them into the lawn if the layer is light enough that grass shows through afterward. Rake or shred heavier drifts and move them to beds or the compost pile. A thick, unshredded mat left on the lawn over winter can smother the grass and encourage snow mold.

When is the last lawn fertilization in the Midwest?

Purdue's research supports a late-season nitrogen application once top growth slows but the grass is still green, typically late October to November in zones 5–6 and earlier in zones 3–4. Do not apply to frozen ground. In Wisconsin it is prohibited.

How do I store dahlia tubers?

After frost, dig them carefully, let them air-dry briefly, and pack them in slightly damp peat, vermiculite or wood shavings in a cool (about 40–50°F), dark place. Check them monthly through winter for rot or shriveling.

Sources

1. Growing Garlic in Home Gardens, University of Minnesota Extension
2. When should I plant garlic?, Iowa State University Extension
3. Planting Bulbs, University of Illinois Extension
4. Digging and Storing Tender Bulbs, Michigan State University Extension
5. Fall Fertilization, Purdue University Turfgrass Science
6. Late Fall Lawn Care, University of Minnesota Extension
7. Fall Leaf Mulching Is Good for Your Lawn, University of Minnesota Extension
8. Consider Pollinators During Fall Garden Cleanup, University of Illinois Extension

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