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

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Kohlrabi 

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 editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on .