Leafy crops and root crops tolerate cold much better that fruiting plants. The flavor of some vegetables improves, often becoming sweeter or milder after exposure to cold. Selecting specific varieties which are bred for their cold tolerance will also give longer lasting harvests. Typically, the crops that have good cold tolerance are those that are planted in early spring. These are the same crops that will also do well towards the end of the growing season.
 
Spinach will produce leaves late into the fall under cover, and then when the freezing temperatures hit, it will hunker down waiting for the first warm weather of early March to continue growing. The roots and crown of the plant will have been protected in the soil even if the top leaves look horrid. New leaf growth will renew your faith in the seasons while supplying a fresh salad for your table in late winter or early spring. The varieties ‘Space’, ‘Winter Bloomsdale’ and ‘Giant Winter’ have exhibited exceptional hardiness.
 
Lettuce will produce cutting leaves if non-heading varieties are selected. These will not survive severely hard freezes, but leaves can be cut from the sides, leaving the crown of the plants well into December. More cold tolerant varieties are listed as ‘Red Oak Leaf’, ‘Winter Density’, and ‘Rouge d’Hiver’. Some seed companies sell winter leaf lettuce mixed seed packets containing only cold tolerant varieties of lettuce.
 
Arugula is a spicy leaf used alone in a salad or mixed in with other greens. It has great cold tolerance. Varieties commonly available are ‘Astro’ and ‘Sylvetta’. Arugula tends to bolt in the heat of summer, preferring to grow in the colder weather.
 
Totsoi is an Asian green that can be cooked or eaten raw. There are many different Asian greens in the bokchoi group that all have superior cold hardiness. Some varieties are ‘Mei Qing Choi’ and ‘Tokyo Bekana’. This group includes the tart mustards that are commonly steamed or used in salads.
 
Swiss chard is a leaf crop in the same family as spinach and beet. It is treated much the same as spinach, going dormant during the coldest periods and producing a resurgence of growth in the first warm days of late winter. Pick the leaves and leave the growing crown. ‘Bright Lights’ is a good variety with cold tolerance.
 
Kale is a favorite cold weather green. With variety names like ‘Winterbor’ and ‘True Siberian’ their cold hardiness speaks for itself. Kale can be harvested through the winter by just knocking the snow off of and cutting the leaves off of the stem. Some will keep producing leaves all winter long.
 
Parsley is one herb that will take the cold. It can be grown in the same way as these other greens, with a bit of winter protection. There are flat leaf and curly varieties, but the curly types are more cold tolerant. ‘Forest Green’ is a common variety planted to winter over.
 
Root crops planted in mid to late summer will produce most of their root growth before going into the cold temperatures and less light time. Roots can be given protection to be harvested throughout the fall and winter from their tucked in beds. Potatoes are the exception. They are tuber, not a root.
 
Carrots become sweeter when keep in the soil during cold weather. ‘Napoli’ is a good winter carrot as is ‘Autumn King’. White and yellow turnips are wonderful for extended season gardens. Like carrots, they develop much more sweetness after experiencing some cold. ‘Hakurei’, ‘Orange Jelly’ and ‘Amber Gold’ are great keepers. Radish is a quick growing crop that can be planted through October and still produce viable roots for eating. Just about any radish variety will be successful for later harvesting.
 
Leeks are a commonly kept over the winter, sometimes with no more protection than a layer of straw placed over them. In order to have winter leeks, seeds need to be started indoors in late winter to early spring and the transplants set out usually in late April or May. Leeks take a long time to produce large, white stems of substantial diameter often 100 days or more. ‘Saint Victor’, ‘Alaska’ and ‘Broad London’ are known for their ability to hold in cold weather.
 
For that extended harvest, select some appealing vegetable varieties and figure out what system would work best in your yard. Often the harvest season can be lengthened by a month or more. Most systems do not require a heavy investment of money or equipment just a bit of ingenuity and a desire to extend the harvest.