Refresh Your Vegetable Garden for a Fall Crop

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Posted on 09 August 2010

In the dog days of summer the vegetable garden often takes a nose dive as heat, drought, disease and insects take their toll on plants. You may think about just letting it go, but this is actually a great time to replant for a great fall harvest. Read more about getting a second wind in the vegetable garden...


When spring and summer vegetables decline, remove and replace them for a fresh new planting ready for harvest in the fall.If your vegetable garden is looking a little ragged, it may be time for a make-over. Have the lettuce plants bolted, the beans stopped flowering and the squash succumbed to vine borers, virus or powdery mildew? Then take them out and plant something new now for later in the season! Late summer is the perfect time to plant some new crops for fall harvest. The trick to getting another crop from your garden is to select the appropriate plants that will thrive in the cooler days ahead.

Bush beans and summer squashes stop growing in cool weather and are killed by frost. Although basil is frost-tender, it grows quickly so can be part of a fall garden is sown early and protected from cold weather.Although some varieties of beans will mature in only 45 days, that is usually not enough time to produce a crop when planted in August in the upper Midwest – but it may be worth taking a chance that global warming will result in a later than normal first frost and allow your planting to make it through. A few frost-sensitive plants will grow so quickly you can get something before frost arrives. Basil is a fast-growing herb, especially in the heat of late summer, ready for harvest in about a month. Floating row cover or other plant covers can also be used to help extend the season for sensitive plants, as we sometimes enjoy a few weeks of good growing conditions after the first frost.

Kale is a very hardy vegetable that will survive late into the growing season.Some vegetables, however, will tolerate a fair amount of frost and keep growing even when temperatures are in the low forties. Kale and a few other cool-season crops can even survive cold down to about 20ºF. These are the best choice for mid-summer sowing. Most greens, several root crops, and some other vegetables will mature in a short enough time and continue growing well after the first frost. Late season beets, radishes, lettuce, chard, kale and others also develop sweeter flavors in the cooler temperatures of autumn, so are often of better quality than the same types grown in spring or summer. You don’t have to worry about radishes, lettuce and spinach bolting (going to seed) and becoming bitter in response to long, hot days. And insect and disease pests are not as much of a problem for some crops.

Vegetables for Fall Harvest
 Killed by frost
 Survives Light Frost
   Asian Greens
   Dill (leaces)
   Swiss chard
Survives High 20's
   Green Onion
   Mustard Greens
Very Hardy, to 20F
   Collard greens

Other than the tender plants killed by a frost, these vegetables will require little or no frost protection. Those plants which can only survive a light frost should be harvested before a heavy freeze. Root crops such as beets and radishes should be harvested or mulched heavily before a hard freeze.

Lettuce grows well in the cooler temperatures of autumn, producing sweet, tender leaves.

In order to get the best crop possible, determine the days to harvest and the average first frost date for your area, then calculate backwards to figure out when each type should be planted so they will have a chance to mature before being killed by cold weather. Quick-maturing vegetables, such as turnips and leafy greens, can be planted much later than more slow-growing types.Both the roots and leaves of beets can be eaten. But remember that you can harvest some crops – especially leafy greens – before maturity, when the leaves reach full size (with the added benefit that these younger leaves are generally more tender than mature leaves). Note that there is considerable difference in varieties of the same crop. Some cultivars are more suitable as a fall crop than others. Leaf lettuce is a better choice than heading types since you don’t have to wait for the plant to form a head.

Most of these crops will do just fine when sown directly in the garden. Rapid germination is the norm during the warm days of late summer (my arugula seedlings were up in 4 days!). But you should consider transplants for some – especially cabbages and other crucifers – to ensure they have sufficient time to mature (or if you’re a little behind schedule getting things into the ground).

Spinach does not bolt or become bitter when grown as a fall crop.Before replanting, clean up the garden area. Remove all of the roots of the previous plants and any other crop residue, turn the soil and mix in compost or fertilizer (if needed – most root crops do not need this as too much nitrogen will produce wonderful top-growth with small roots). When seeding in late summer, you may want to place the seeds a little deeper than recommended to get them into cooler and moister soil. Shading the newly planted seeds and seedlings (with row covers or by planting on the shady side of tomatoes or other taller plants that will come out later) will help protect them from the hot sun. The soil can dry out and crust over quickly in late summer, preventing seeds from germinating well, so keep an eye on soil moisture and water if rainfall is not adequate. A thin layer of compost or mulch over the newly seeded area can help prevent a crust from forming.

Radishes can be mulched to protect the roots and soil for harvest after exposed ground freezes.Consistent soil moisture is very important for successful fall crops. Seedlings will suffer (or expire) during the hot days of late summer if the soil is not kept evenly moist until they are well established. Steady water allows the plants to produce continuous, succulent growth. Overhead watering on hot days will help cool the leaves and soil.

Mulching around root crops as the weather cools will help retain soil warmth so plants will continue to grow and you can harvest the roots well after exposed soil freezes.

I devote one raised bed in my garden to garlic, and once it is harvested in July, I replant with an assortment of fall crops. The next garlic planting goes into another bed (usually where the tomatoes or squash were) in late September after the other plants have been killed by frost or disease.

Try planting a few new veggies now and once the first frost arrives to nip the tomatoes you’ll still have lots of tasty vegetables to harvest from your vegetable garden!

– Susan Mahr, University of Wisconsin - Madison

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