Know When to Plant What: Find Your Average First Fall Frost Date

Reader Contribution by Staff
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To determine your optimum dates for sowing fall crops, add three weeks to the days to maturity ratings listed below or shown on your seed packs to compensate for days that are getting shorter. Then count back from your average first fall frost date to find the date you should sow each crop. (To find your average first fall frost date, search by state in the tables provided by the National Climatic Data Center.) Cool-season plants will continue to grow a little after nights turn chilly, but they will make most of their new growth early on, while the weather is still warm.

Many of the best crops of fall — including salad greens and various cabbage cousins — will refuse to germinate in soil warmer than 85 degrees, so the seeds are best started indoors (on a 90-degree day, surface soil temperatures may actually be 110 degrees or more). The procedure for growing seedlings is the same as in spring (see Seed Starting Basics), but care for transplanted seedlings requires some extra hardware. Insect pressure in late summer is severe, so use homemade or purchased lightweight row covers to exclude critters. (See The No-Spray Way to Protect Plants) It helps to shade each seedling with a light-colored flowerpot, pail or other cover for two to three days after transplanting. Protected from scorching sun, the seedlings can concentrate on growing reliable roots.

Cabbage and broccoli seedlings need to be planted at least eight weeks before the first fall frost, and as long as their roots are kept moist, they seem to benefit from a spell of hot weather as late summer days become shorter. When set out so late that they miss the last warm spells, cabbage cousins tend to stop growing too soon. Whether you’re working with seedlings you grew yourself or bought at a store, get them in the ground as soon as you can.

FALL HARVEST CROPS

Days to Maturity

beets 55 to 60
broccoli 70 to 80
Brussels sprouts 90 to 100
cauliflower 55 to 65
cabbage 70 to 80
carrots 85 to 95
Chinese cabbage 75 to 85
cilantro 50 to 55 (leaf); 90 to 105 (coriander seed)
collard greens 60 to 100
daikon radishes 60 to 75
green beans 50 to 60
green onions 50 to 60
kale 40 to 50
kohlrabi 50 to 60
leeks 100 to 120
lettuce (leaf) 40 to 50
lettuce (head) 70 to 85
mustard greens 30 to 40
onions (seeds) 130 to 150
onions (sets) 60 to 80
peas 50 to 60
radishes 25 to 30
rutabaga 70 to 80
spinach 50 to 60
Swiss chard 30 to 50
turnips 55 to 60

Contributing editorBarbara Pleasantgardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visitingher websiteor finding her on.