Start with your average first fall and the on the seed packet. Add about 14 days, because shortening days and cooler weather slow growth in fall, and count that total back from your frost date. Frost-tender crops such as beans, cucumbers, and squash need another 14 days on top of that, because they must mature at least two weeks before frost to give a reasonable harvest. For cabbage-family crops, setting out instead of sowing seed lets you plant a few weeks later. The This Week page on this site shows what can still go in now for your ZIP code.
The quickest crops go in last. Radishes, arugula, mizuna, tatsoi, and leaf lettuce cut as baby greens can be sown about 6 weeks before your first fall frost, and several small sowings a week or two apart keep a harvest coming. These are that tolerate light frost, so they can keep producing after the first frost, especially under . Lettuce and spinach seed poorly in soil above about 70°F, so if the weather is still hot, sow in the evening, keep the bed moist, and shade it until seedlings come up.
Full-size leafy greens need a little more time. Lettuce, mustard, and turnips grown for greens can go in about 7 weeks before your first fall frost; spinach and kohlrabi about 8 weeks. Kale and collards do best from transplants set out about 8 weeks ahead. Hardy crops such as kale, spinach, cabbage, and turnips can keep growing until temperatures drop to about 20°F, and many taste sweeter after a few frosts. Lettuce, chard, and Chinese cabbage tolerate light frost, around 30 to 32°F, but need protection when it gets colder.
Roots and heading crops need the longest lead time. Beets, carrots, and turnips grown for roots need about 10 weeks or more, depending on variety. Broccoli, cabbage, and cauliflower do best from transplants set out 10 to 12 weeks before your first fall frost, and Chinese cabbage about 11 weeks ahead. Rutabagas need about 14 weeks, and Brussels sprouts transplants need 90 to 100 days. If you have missed these windows, choose the fastest-maturing variety you can find, or switch to quicker greens.
A few crops go in around or after the first frost. Garlic and shallots are planted in fall for harvest the following summer, usually around the time of your first fall frost so they can root before the ground freezes. fill empty beds: crimson clover and hairy vetch about 8 weeks before your first fall frost, and winter rye as late as about 4 weeks before. Keep row cover on hand for every fall planting. First frosts are often followed by weeks of mild weather, and a few degrees of protection on one cold night can carry a crop through.
- RadishThe fastest vegetable in the garden — 25 days from seed to plate, with almost no room for error.
- ArugulaA peppery salad green that goes from seed to plate in a month — and to seed in another two weeks.
- LettuceA cool-season leaf crop that thrives in spring and fall, sulks in summer heat.
- SpinachA cold-weather green that gives you leaves when almost nothing else will grow.
- KaleThe cold-weather workhorse that improves when everything else quits.
- Tarnished Plant BugMobile brown bug with yellow triangle on back. Causes cat-faced strawberries, pitted beans, and flower drop across many crops.
- Cabbage MaggotBrassica transplants wilting and dying as white maggots tunnel through roots at or below the soil line.
- Carrot Rust FlyRusty tunnels through carrot and parsnip roots made by small white maggots feeding inside the root.
- Corn Earworm / Tomato FruitwormCaterpillars eating corn kernels from the tip; same species bores into tomato and pepper fruit. Often called 'tomato fruitworm' when found on tomato.
- Crown RotThe base of the plant turns brown and soft at the soil line, and the plant collapses — caused by wet-soil pathogens attacking the crown.
- How can I extend my growing season in fall?Row cover fabric, cold frames, and switching to cold-hardy crops are the three most reliable tools for extending production 4–6 weeks past your first fall frost.
- What is a last frost date and how do I actually use it?Your last frost date is the average date of the final freezing night in spring — it's a probability, not a promise, and smart planting adds a buffer of 1–2 weeks beyond it for cold-sensitive crops.
- There's a surprise frost forecast — what should I cover and with what?Cover warm-season transplants and seedlings with row cover fabric or old bedsheets — not clear plastic sheeting directly on leaves — and place covers before sundown to trap daytime heat.
- Why did my broccoli skip making a head and go straight to flowers?Broccoli bolts when it experiences heat or stress during head formation — once it starts flowering, the head is unsalvageable, but timing adjustments can prevent it next season.
- How do I know when to harvest garlic?Harvest garlic when roughly the lower third to half of the leaves have turned brown and dried — this corresponds to the bulb having formed its full complement of papery wrapper layers.