University of Vermont Extension 
Department of Plant and Soil Science

Summer News Article


Dr. Leonard Perry, Extension Professor
University of Vermont
Having a fall vegetable garden is fun, easier than gardening at other times of the year, and extends your season for fresh produce.  Many claim the same vegetables grown in the fall are tastier and "sweeter" than those earlier in the season.  Late summer is the time to start crops that mature quickly and take cooler weather. 
Growing vegetables in fall you can take advantage of cooler weather outdoors, and avoid most weeds and insects that have come and gone.  Generally fall brings more rain, and with less heat, you'll have less watering.  Some crops prefer and grow best in cooler weather, such as lettuce and traditional "cool season" crops as carrots, beets, cabbage and kale. 
To decide what to grow, there are a couple considerations.  Look at the days to maturity listed on seed packets to see if your crops will have enough time to mature before frost.  Keep in mind some crops can be picked young, as with frequent picking of lettuce leaves, or young beets, carrots and turnips. Radishes are a root crop best picked when mature. Avoid crops such as bush snap beans that, although they mature quickly, require warmth and are killed by frosts and cold.
Crops also will vary in how much frost and cold they will withstand.  Often we will get a light frost, followed by a warm period of "Indian Summer" prior to harder frosts and colder temperatures.  Just a little protection such as from thin fabric "floating row covers" may be all that is needed to get your crops past the first light frosts.  Many other home frost remedies can be seen in fall gardens prior to cold nights including corrugated fiberglass panels, old towels or blankets and sheets (held above plants on some form of boards or support), and milk jugs with bottoms cut out over individual plants.  Some use plastic water-holding walls around plants.
Vegetables that withstand light frosts (and their days to maturity) include broccoli (50-70 days), carrots (50-60 days), cauliflower (60-80 days), cilantro (60 to 70 days), kohlrabi (60 to 70 days), leaf lettuce (40 to 60 days), mustard greens (30 to 40 days), spinach (35 to 45 days), Swiss chard (40 to 60 days), and turnips (50-60 days).  From the day you want to plant, count out this number of days to see if your crops will mature before the usual first hard frost for your area.  Keep in mind that cultivars differ in their days to maturity, so look for ones with the fewest days.
Hardier vegetables, surviving temperatures into the high 20s (F) include beets (50 to 60 days), (green onions (60 to 70 days), peas (70 to 80 days, longer than in the spring), radish (25-35 days), and turnips (50 to 60 days).  Hardiest vegetables, surviving temperatures to the low 20s, include Brussels sprouts (90 to 100 days), collard greens and kale (both 40 to 65 days).  Plant garlic after the first frost but two to four weeks before the first heavy frost, and shallots after the first frost, for harvest the following summer.  These are planted late to avoid stimulating top growth only to be killed by cold.
Fall gardens can be planted in new beds, or ones vacant after the harvest of many of the same crops grown in spring.  Just make sure to rotate crops for best growth and to minimize diseases and pests.  Don’t plant a crop in the same part of the garden where it was grown in the last couple years.

If replacing spent or dead crops, make sure to remove all plant residue and roots, adding a fresh supply of compost or rotted (weed-free) manure and other fertilizer as called for by a soil test.  If you have fertilized well through the season, no additional fertilizer may be needed.  Or, if plants appear to be growing slow and are yellowish, you may water with a liquid fertilizer for vegetables, or apply a light application of a general purpose dry fertilizer along the rows.
If sowing seeds in hot weather, a couple methods can be used to provide the cool soil that fall crops prefer to germinate and grow best.  You can lay some form of shade such as snow fencing or lattice supported on boards, or a shade cloth fabric over the bed while seeds germinate and plants become established.  It’s best not to use a frost blanket as you would use later in fall, as this will keep seedlings too warm. 

Or you can water the beds to cool the soil, cover with a few inches of straw, then water again.  Remove the straw in a few days and sow in the now cooler soil. Replace the straw as mulch once plants are growing. Simply using a thick layer (6 inches or so) of straw on some root crops as carrots can keep the soil from freezing and extend their harvest into early winter.  As with vegetables sown at other times, make sure to keep them watered if rains don't.
To extend your growing season even more, consider growing in coldframes.  These can be as complex as commercially made dual-wall solid polycarbonate panel units, with automatic venting.  If these have some additional heat, as from a heating cable, they are called "hotbeds". Perhaps most simple is a row of straw bales around plants supporting an old window sash or wood frame with corrugated fiberglass panel.  If not automatically vented, make sure to vent on hot days so plants don't get overheated.  Since covered and not exposed to rain, make sure to check often for watering.  Using coldframes you can have vegetables well into winter, even after snow falls.

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