#garden tips

Know Your Hardiness Zone and First Frost Date

Knowing your plant hardiness zone helps you choose crops that will thrive in your location. It’s especially important for determining whether a particular plant can survive the winter in your region. This information is most useful when planting perennials. For vegetable gardeners and seed savers, it’s also essential when growing biennials for seed production.

The USDA’s Plant Hardiness Zone Map divides the United States into zones according to the “average annual extreme minimal temperature”. Consulting the USDA hardiness zone map will help you determine whether a particular plant can thrive and survive in your part of the country. 

Knowing the average first frost date for your region will allow you to calculate “planting deadlines” so that your young plants have time to mature before the temperatures fall and the first frost hits. 

These two tools will help you determine not only which crops you should plant but also when you should have those crops in the ground.

Fall Planting for Food Consumption

Choose Crops Wisely

Two types of plants are good bets to thrive when planted in midsummer—those that mature quickly and those that tolerate frost.

Paying attention to maturation time is key because crops planted in the summer months take longer to mature than those planted in the spring. As the summer turns to fall, the days shorten and the air cools. The lessening daylight and cooler air temperatures combine to slow plant growth. 

(The good news? While your fall plantings take longer to mature, they will face fewer threats from pests this time of year!)

To ensure your plants mature in time for harvest, add a few extra days to the “days to maturity” guidelines typically found on seed packets. Then count back the total number of days on your calendar to arrive at your summer planting date. 

Quick-Maturing Crops

Sow these crops in late June and July to squeeze in a second harvest before the warm season ends. Radishes are quick to mature

Quick-maturing vegetables include: 

Beets

Snap beans

Carrots

Cucumbers

Kohlrabi

Radishes

Spinach

Swiss chard

Zucchini

And if some of those quick-maturing crops don’t mature fast enough to elude the first frost, you can easily use row cover or garden fabric to protect them from too-cool temperatures.

Tip: Look for varieties of each crop that mature early, especially when choosing crops that prefer lots of heat, such as cucumbers and beans.

Frost-Tolerant Crops

Most brassicas, such as cabbage, are frost-tolerant

Crops that will tolerate a light frost and keep growing even when temperatures drop include:

Most brassicas 

Broccoli 

Brussels sprouts

Cabbage

Collard

Kale

Kohlrabi

Most Asian greens (also brassicas)

Arugula

Beets

Carrots

Loose-leaf lettuce

Parsnips

Rutabagas

Spinach

Turnips

Many herbs

Some of these cold-tolerant vegetables—particularly carrots, collards, kale, and Brussels sprouts—actually taste better when grown in cool weather as they react to cold by producing sugars which then sweeten them. 

Take note, however—while spinach, turnips, and rutabagas can be direct sown, you may need to start most brassicas indoors weeks before the midsummer planting period.

Cool and Enrich the Soil

Summer, of course, brings heat, and toasty temperatures can easily roast newly sprouted seeds. The best way to prevent that from happening is to keep the soil moist, mulched, and shaded, if possible. Natural shade from a trellis or tall plant, for example, can be used to create a cool location for seeding a second crop.

Don’t forget the importance of rich soil—be sure to replenish the nutrients in the soil between plantings by mixing in compost and organic fertilizer. Learn more about soil health.

Use Cold Frames and Row Covers

Cold frames and row covers can be used to prolong the growing season by raising the soil temperatures in the cooler seasons and shielding crops from the elements, especially wind. 

How to build a simple cold frame:

Construct a box using wood planks (We find that 2×8 planks work well!)

Cover with an old window

Tip: Most crops can benefit from a light row cover to act as a wind buffer. When using row cover, make sure to keep some separation between the fabric and the plant itself, especially when covering smaller greens. Half-inch metal conduit bent into hoops works well for this, but easy-to-cut 9-gauge wire is also a great option. Both materials are sturdy and can be shaped into low tunnels to support a covering of your choice.