Timing is everything especially when deciding the right time to plant vegetables. Some vegetables thrive in the heat of summer while others grow best in the cool temperatures of spring and autumn.
Vegetables that love the warmth of summer are often native to the tropics or subtropics. Many cucurbits, nightshades and tubers are best grown in warm weather. Warm‐weather vegetables include aubergines (eggplant), lima beans, snap beans, corn, Crowder peas, courgettes (zucchini), cucumbers, Malabar spinach, marrow, New Zealand spinach, okra, peppers, potatoes, pumpkins, soybeans, squash, sweet potatoes and tomatoes.
Many brassicas, alliums, leafy greens and root crops grow best in cool weather. Cool‐weather vegetables include beetroot (beets), broccoli, Brussels sprouts, cabbage, carrots, cauliflower, celeriac, celery, celtuce, Chinese cabbage, corn salad, cresses, endive, escarole, fava beans, garlic, kale, kohlrabi, lamb’s lettuce (mache), leeks, lettuces, mustard, onions parsnips, peas, radicchio, radishes, salsify, shallots, spinach, swedes (rutabagas) and turnips.
A few crops excel in all seasons. Swiss chard grows well in warm or cool weather. It produces greens throughout the summer but will also withstand a mild frost. Collards also thrive in hot, as well as cool, weather.
See the articles under Planting and Care for instructions on when to plant and how to care for each type of warm‐season, cool‐season and all‐season vegetable.
Peas are often the first of the cool‐season crops to be planted in northern gardens. Seeds can be sown as soon as the snow melts and the soil is workable. Lettuce and spinach can also be planted in early spring. (For later spring plantings, sow bolt‐resistant varieties. See Growing Leafy Greens articles for tips.) Lamb’s lettuce (mache) is another early spring favourite. Cool‐season brassicas, alliums and roots are other main crops in the spring garden.
Warm‐weather crops are not frost‐tolerant and should not be planted outdoors until all danger of frost has passed. One way to get a jump start planting heat‐loving vegetables is to start seeds indoors or buy seedlings and set them into the garden as transplants.
Tomatoes and peppers need a long growing season and are best grown from transplants in short‐season northern climates. Tomato transplants should be put in the garden one to two weeks after the last frost.
Planting the Autumn Garden
For many gardeners, planting begins in the spring and ends by mid‐summer. It’s possible, however, to keep planting some crops through late summer for an autumn – or even winter ‐ harvest. For late summer planting, choose vegetables that not only tolerate cold, but that mature quickly. Consider the number of days to harvest when selecting a variety for the autumn garden. And while many cool‐weather crops will survive a frost ‐ and still be good to eat ‐ they won’t grow much after exposure to frost.
Good vegetables for the autumn garden include leaf lettuces, spinach, radishes and peas. When planting late‐summer peas, sow seeds up to two inches deep if the soil is hot and dry. While peas can tolerate a moderate freeze, however, they’re more sensitive to freezing in the autumn than in the spring.
Brassicas are not only frost‐tolerant, but a light frost often improves their flavour. Broccoli, cauliflower and the hardier cabbages can even take a hard freeze. Kale is so hardy it will even come up in the snow! Brussels sprouts are another late‐season winner and taste better after a hard frost. Sow Brussels sprouts four months before first frost.
Hot Weather Planting Tips
Planting crops in the heat of summer may require a few different techniques from spring planting. Spinach and lettuce, for example, don’t germinate as well in hot weather, therefore sow seed more thickly. Provide temporary shade for young cool‐weather seedlings until temperatures cool down. Water the soil prior to planting, and plant ‐ or transplant ‐ late in the day.
Seedlings started during hot weather require special attention to watering. Water thoroughly after planting, and keep watering throughout the season.
During the early spring and late autumn, be prepared for an unexpected frost. Watch weather forecasts and keep tarps and other coverings handy. If a frost is predicted, cover sensitive crops such as cucurbits (squash and cucumbers), nightshades (tomatoes, aubergines and peppers) and legumes (peas and beans).
What if cold‐hardy vegetables are subjected to a freeze and you want to harvest them? Leave them on the stalk until they thaw out, then harvest. Cutting them while frozen will result in limpness. Thawed first, they maintain their crispness.
With a little planning – and a little help from Mother Nature – you can extend your growing season and reap even more fresh vegetables from your garden!