The traditional planting season for the open garden begins in the cool, wet weather of early spring. Depending on the vegetable, the harvest begins three weeks to three months later. In this vast country, “early spring” is a way of saying “cool weather with frequent rains to come,” and it can occur from January to May, depending on the part of the country.
Frost Dates
The cooperative extension office or even a local nursery can tell you the frost dates for your area, or see First and Last Frost Dates for an estimate. In spring this is the approximate date of the last spring frost; in fall it is the approximate date of the first fall frost. These dates are an average over the years for a given area and serve as guidelines when planting seeds and seedlings.
When to Plant
Plant vegetables in batches, according to their weather preference. There are cool-season crops, warm-season crops, and hot-weather crops. The cool-season crops are the seeds you can sow before the last frost date in spring. Plant warm-season crops later in spring when the soil has warmed a bit, and plant hot-weather crops last of all.
A variety of vegetables have adapted to every climate on the globe, from the short summers of the arctic to the year-round growing seasons of the southern states and subtropical regions. But most vegetables are seed-sown annuals that evolved where the early part of the growing season is cool and rainy. This is springtime, and seed packets for most vegetables suggest planting sometime in spring.
Just when in the calendar year spring occurs varies according to geographic location. In Anchorage, Alaska, this is in June, but in San Jose, California, “early spring” arrives in late January. In fact, the planting season in San Jose is almost all year around. For most of the country, the planting seasons are somewhat more distinct.
Early Spring
In warm regions, early spring and late winter overlap. In the North this is “when the ground dries enough to be worked” and “when the frost is out of the ground.” During these cool few weeks, some frost-resistant cool-season plants can be started successfully in the open garden: peas, onion sets, fast-growing radishes, and early leaf lettuces. In the cool North, gardeners force the season by planting under hot caps and plastic tents, cheating the cold as best they can.
Spring
This is the long, moderately warm period after the last frost and before the first real heat. Most of the cool-season vegetables are sown at this time, including head lettuces, spinach and other leafy greens, parsnips, and carrots.
Late Spring
When the night chill is gone and days begin to head toward 80 degrees, late spring has arrived.
Now it is safe to set out warm-season crops such as tomatoes, peppers and squash, as well as hot-weather crops such as watermelons and sweet potatoes.
Midsummer
In the cool northern tier, make successive sowings of snap beans, broccoli, cabbage, carrots, lettuces, and parsnips for early-fall harvesting. Where summer is too hot for sowing seeds outdoors, start them indoors or in a cold frame with some protection from heat and drying winds. In very hot regions, winter is usually mild, and sowing for the second season is delayed until the heat lets up and there is hope of rain.
Late Summer, Early Fall
In the South, sow winter crops of hardy vegetables such as beets, broccoli, and spinach.
Winter
In mild climates pull kale, carrots, and other root vegetables all winter. Almost everywhere parsnips, which taste better after a frost, can overwinter and be harvested as an early-spring crop. In mild regions plant peas in October for extra-early spring picking.
Perennials
Unlike the majority of vegetables, which are annuals, perennials must survive the year around. For these plants, winter weather is significant. Be sure to choose perennials that are hardy in your region. Before you order artichokes or any of the other perennial vegetables, make sure they can survive your winter.
Vegetable Hardiness
Cool-Season Crops
The following plants tolerate some frost and air temperatures between 55 and 70 degrees.
| Asparagus | Kale | Radish |
| Beet | Kohlrabi | Spinach |
| Broccoli | Lettuce | Turnip |
| Brussels sprouts | Onion | Turnip greens |
| Cabbage | Parsnip | |
| Collards | Peas |
Semicool-Season Crops
The following vegetables tolerate some cold but no frost at maturity.
| Artichoke | Cauliflower | Endive |
| Carrot | Chard | Potato |
Warm-Season Crops
The following crops are readily damaged by frost and are best adapted to 65 to 80 degrees. They rot in cold soil.
| Beans | Cucumber | Pumpkin |
| Cantaloupe | Muskmelon | Squash |
| Corn | Pepper | Tomato |
Hot-Weather Crops
Planted when temperatures are between 65 and 80 degrees, these plants require a long growing season and do well in temperatures above 80 degrees.
| Lima beans | Okra | Sweet potato |
| Shell beans | Peanuts | Watermelon |
| Eggplant |