The harvest season may be upon us, but that doesn’t mean the growing season has to end. If you live in an area that enjoys mild temperatures well into the autumn, now is the time to plant cool-season veggies in your garden to extend your growing season by a couple of months. Even if you live in an area that receives snow during the winter months, you may still be able to plant a few cool-season vegetables, provided you house them in a greenhouse, cold frame, or hoop house. So what exactly constitutes a cool-season crop, and what materials will you need to extend your growing season?

What are Cool-Season Vegetables?

As their name suggests, cool-season vegetables thrive when the temperatures dip into the 40-to-50-degree Fahrenheit range and seldom need additional protection when temperatures fall into the 30s. Conversely, these same crops are ones that don’t do as well during the summer, often bolting quickly when temperatures increase into the 70s and ceasing to grow altogether when temperatures get above 80 degrees.

Two Types of Cool-Season Veggies

cabbage in the garden

Cool-season crops fall into two categories: hardy vegetables, which are cold-tolerant, and semi-hardy vegetables, which do best when the temperature is between 40 and 50 degrees Fahrenheit. Hardy vegetables not only germinate in cold soil, but they’re also most likely to survive freezing temperatures and heavy frost for a small window of time. If you live in an area where the temperature regularly drops below freezing (32 degrees Fahrenheit), then these crops would do best sheltered by a cold frame. While they may not continue to grow throughout the winter, you can continue to harvest them. Hardy crops include asparagus, broccoli, brussels sprouts, collards, cabbage, peas, radishes, rhubarb, spinach, turnips, kale, leeks, mustard, parsley, garlic, chives, kohlrabi, and horseradish.

Semi-hardy vegetables may be able to handle light freezing and frost, but don't count on them to survive anything extreme or that lasts more than a day. These crops include celery, cauliflower, carrots, beets, chicory, globe artichokes, endives, lettuce, parsnips, salsify, potatoes, sorrel, and many herbs.

As you can see, there’s a wide variety of vegetables that thrive when the temperatures fall and can take center stage in delicious winter stews, soups, and dishes.

When to Plant Your Cool-Season Veggies

planting green onions

If you’re thinking of growing cool-season vegetables, start sowing seeds or planting when the temperature highs are in the low 70s at most. In parts of the country where temperatures stay in the upper 70s and 80s well into September, you may have to hold off on planting until later in the month or early October. Alternatively, you can get a jump-start on the season by starting your vegetable seeds indoors.

Seed-Starting Indoors

If you plan on starting these vegetables from seed, you can do so indoors a few weeks before you plan to plant them outside. If, for example, the average daytime-temperature high in your area doesn’t fall below 70 degrees until the first part of October, you'll want to start your seeds indoors around the second week of September. Broccoli, cabbage, brussels sprouts, collards, artichokes, cauliflower, celery, and rutabagas are all crops that can be started indoors.

Direct Seed

On the other hand, some vegetables grow best when sown directly into the soil. For these crops, it’s best to wait until the temperatures fall below 70 degrees to plant. If you can, check the temperature of the soil before you plant them to increase their chances of germinating and growing. Pick up a thermometer at your local garden shop to get an accurate reading. Vegetables that fall into this category include kale, peas, radishes, kohlrabi, spinach, lettuce and other leafy greens, Swiss chard, potatoes, carrots, beets, endives, Asian greens, and turnips.

Prepare for the Elements

row cover on garden plants

Since freezing weather can arrive at any time in the mid to late fall, you'll want to keep row covers on hand to protect your plants while they’re young, especially if temperatures tend to fall below the plants’ tolerance level. Even the hardiest of plants would be in for a shock in the event of a sudden freeze a week or two after planting. Floating row covers protect plants from frost and keep temperatures slightly warmer than they'd be without them.

If you don’t have the garden space for a greenhouse, it's okay. Hoop houses and cold frames are space-conscious, budget-friendly ways to extend the growing season and protect your vegetables. Hoop houses can be made in an afternoon using PVC pipes, twine, and a plastic row cover, and they can provide great shelter to your all of your garden plants, regardless of whether your beds are raised or in the ground. Cold frames can be made in a weekend and are often made of rot-resistant wood and glass. If you or your neighbors installed new windows or replaced any glass shower doors this year, you can use the old ones to build a cold frame. If you plan on harvesting plants in the winter, hoop houses and cold frames will allow you to do so, even when there’s snow on the ground.

While you may not be gardening outside as much, there’s no reason to put your gardening tools when the weather changes. With a little bit of care and protection, you can enjoy fresh vegetables with your meals all fall and winter long.