Cool Season Vegetables

Robert J. Souvestre  |  12/21/2011 2:12:05 AM

Easy to grow broccoli should be harvested when heads are smooth and uniform.

The sweetest turnips are around 3-inches large and occur after plants receive some cool weather.

Cover cauliflower heads with the plant's large leaves to ensure a pure white head develops.

The vegetables we grow during the cool season are some of the most delicious and nutritious that our home gardens can produce. Many of the vegetables we planted in late summer and early fall are ready to harvest – or will be soon. It is important to harvest vegetables at the proper stage for best results, so here are a few guidelines for some common cool season crops.

Root crops are harvested when the root is the proper size. Usually, the top of the root is readily visible at ground level. Harvest radishes and carrots when the root is about 1 inch across. Carrots can be left in the ground once they are mature to be harvested as needed. Turnips should be harvested when they are 2 to 3 inches in diameter and rutabagas (a close relative) when they are 4 to 5 inches in diameter. Beets are best harvested at 2 to 3 inches.

Broccoli heads are not harvested based on the size of the head, but when the largest individual flower buds are about the size of a small match head. Do not allow the heads to remain on the plant so long that some of the buds open and produce a yellow flower. Remember, smaller side heads will develop after the main head has been harvested, so leave the plant in place for additional harvest.

Harvesting cauliflower also depends more on the appearance of the head rather than its size. The curds of the head should be relatively smooth, very much like the cauliflower that you buy in the supermarket. If allowed to stay on the plant too long, the head will begin to separate and lose quality. If you did not blanch your cauliflower by covering the head with the plant’s leaves, it may have a purple, green or yellow tint to it. This does not greatly affect the quality of the head.
 
Leafy crops such as mustard, spinach, Swiss chard, leaf lettuce, collards and turnips should be harvested frequently by breaking off the lowest, largest leaves (this is called cropping). Harvest the entire head of semi-heading varieties of lettuce such as bibb, buttercrunch and romaine when the head is fully developed. Cabbage is ready to harvest when the head is solid and hard.

Cabbage is one of the few crops that may be left in the garden after they are ready to harvest, although the heads may split. If you are going to leave fully formed heads in the garden, twist the head one-half turn to prevent splitting (this slows water uptake by breaking some of the roots).

Snow peas and edible-pod peas are productive, delicious and well worth growing. Harvest snow peas when the pods are full size but still quite flat. Edible-pod peas, such as Sugar Snap peas, should be harvested when the pods are full and round but before the peas inside the pod have fully developed. Both types of peas should be checked daily and harvested frequently.

Bunching onions and green shallots can be harvested anytime during the winter when the tops are large enough. Dig up the entire clump and separate off about one-half of the clump to harvest, and then replant the rest to continue to grow and divide for future harvesting.

Although winter vegetables are generally hardy, new plantings may need to be protected from hard freezes. So will certain vegetables near or at harvest stage. If temperatures below 30 degrees are predicted, young seedlings should receive special attention by completely covering them with a 4- to 6-inch layer of loose mulch such as leaves or pine straw. The mulch may remain over the plants for a few days, but remove it as soon as the freezing episode is over. You can also use fabric sheets, floating row covers or plastic that’s supported so it isn’t in contact with the plants.

Although the plants themselves are quite hardy, the heads of broccoli and cauliflower are prone to cold injury if temperatures drop below 30 degrees. The leaves, flowers and pods of peas may also be damaged by hard freezes. Rather than trying to provide protection, consider harvesting all mature and nearly mature produce before the freeze.

Protect or harvest if temperatures are predicted to go below 30 degrees: fava beans, broccoli, cauliflower, lettuce, peas.

Vegetables that will tolerate temperatures down to the mid-20s with little or no damage: Swiss chard, Chinese cabbage, kohlrabi, mustard, spinach, radishes and turnips (although radish and turnip leaves are moderately hardy, the roots are very hardy).

Vegetables that will survive temperatures in the low 20s and even the teens, especially if given some protection: beets, Brussels sprouts, carrots, celery, collards, garlic, chives, onions, parsley, leeks and shallots.
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