USDA Climate Zones and Other Gardening Tips

This installment of a regular feature devotes most of its space to summer gardening recommendations for each of the USDA climate zones.

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USDA climate zones stretch in bands across the country, each encompassing distinct seasonal growing conditions.


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The shimmering heat of summer lies heavy upon the land. As parading thunderheads pile high in the sky, wait for the first fat drops of precious rain to release the earth's rich fragrance. Later—after the soil's thirst is slaked and the storm rumbles away—feast on fresh corn, beans, cabbage, and tomatoes, and give thanks for the season and for the goodness of the garden.  

Summer Gardening

We try on occasion to bring you detailed gardening suggestions, tailored to the USDA climate zones. Of course, regional variations exist just about everywhere, and advice that's suitable for a general location may have to be modified to suit any particular site. Still, you should find our suggestions pretty close to the mark for your region. Just add your knowledge of local conditions, and get gardening!    


Even in always chilly Zone 3 (where frost can come in early September and the winter temperatures sometimes drop below -30°F), you can plant a second crop of heading lettuce or endive as late as mid-July. Turnips, peas, and kohlrabi can also be seeded up to the 15th of the month. Other greens—such as leaf lettuce, spinach, and mustard—can be sown all month long. Radishes will crop if planted in July or the first half of August, and early turnips (such as Tokyo Cross) should mature if they're sown before August 10th.


You folks up in cool Zone 4, where frosts often occur around the first of October, can plant bush beans, Chinese cabbage, beets, carrots, and Swiss chard through the first week of July. Transplant your all cauliflower seedlings before mid-month, and sow kale and kohlrabi seeds by then, too.You can start endive, lettuce (both heading and leaf varieties), mustard, peas, radishes, spinach, and turnips almost anytime during July. August, however, offers less opportunity: Spinach can be sown until the 15th, and some of the minor greens (corn salad and cress) will beat the frost even if planted later still.


Gardeners in Zone 5 have a relatively wide range of choices available to them. Up to mid-July, brussels sprouts and broccoli seedlings can still be set out, as can cabbage transplants. The 15th of July is the last day for planting seeds of okra, rutabaga (so sweet and mellow on a winter's evening!), summer squash, and heat-loving New Zealand spinach. You can normally plant bush beans, beets, cauliflower seedlings, carrots, and Swiss chard through the third week in July. Chinese cabbage, kale, turnips, parsley (mulch it well and it'll even winter over), and kohlrabi can be started anytime this month.

Come August, you can plant leaf lettuce, endive, and mustard before the 15th. Spinach, radishes, and turnips can probably be put in all month long. Early in August, tip-prune your melons and winter squash. All the energy that would have gone into setting flowers will be thrown into ripening the fruit that's already on the vine.


Since the first frost in Zone 6 occurs about October 20, you folks can still do a good deal of planting. During the first two weeks of July, for example, it's safe to sow bush beans, corn, cukes, melons, summer squash, and rutabaga. Pepper transplants (especially varieties—like Canape and New Ace—that set fruit well in cooler weather) can also be set out till mid-July, as can potatoes. Plant brussels sprouts seedlings, beets, broccoli transplants, Chinese cabbage, carrots, cauliflower (transplants, of course), Swiss chard, collards, kale, kohlrabi, leaf lettuce, New Zealand spinach, and turnips anytime in the month of July.

Zone 6 gardeners can keep busy in August, too. Until the end of the second week, Chinese cabbage, kale, kohlrabi, parsley, and turnips can be sown. Many salad makings (lettuce, endive, mustard, and radishes) can be planted all month, while the fall spinach crop should probably go in around the 15th. And don't forget to sow a cover crop of winter rye in any area of the garden that's finished producing vegetables.


If you live in temperate Zone 7, you can choose among a wide variety of succession crops. With the first frost due around November 1, there's time for many foods to reach maturity. You can still plant limas or bush beans, broccoli or brussels sprouts transplants, carrots, Swiss chard, chicory, early corn, cucumbers, black-eyed peas, New Zealand spinach, and summer squash anytime in July. During the first half of the month, sow melons, soybeans, winter squash, and transplant peppers.

Then, from July 15 to mid-August, you can set out cauliflower seedlings and plant potatoes. During all of August you can sow Chinese cabbage, beets, Swiss chard, kale, kohlrabi (generally the Purple Vienna variety—or the Grand Duke hybrid—will be best for fall), lettuce, parsley, peas, and turnips. Mustard and radishes will get a good start in the cooler weather of late August.


In southerly Zone 8 (where frost often arrives in mid-November), July is too blamed hot to plant some vegetables ... but heat-loving lima and bush beans, corn, cukes, black-eyed peas, pepper seedlings, and soybeans will flourish if planted at any time of the month. You lucky folks can set out tomato and eggplant seedlings until mid-July, and plant seeds of winter squash during the same period. The second half of the month provides prime opportunities to make fall-ripening plantings of watermelons, muskmelons, and rutabagas.

August, being a little cooler, is actually a better month for succession planting in Zone 8 than is July, and is a good time to sow bush beans, beets, broccoli, brussels sprouts, carrots, Swiss chard, endive, garlic (to be harvested next year), kale, and shallots (they'll winter over, too). You can also set out cauliflower transplants and start more potatoes. Things should cool down enough by the 15th to let you safely sow Chinese cabbage, collards, kohlrabi, lettuce, mustard, and tangy sorrel.


In the balmy reaches of Zone 9, where frost holds off until December, both July and August are ideal months for transplanting eggplant, peppers, and tomatoes, and July is a good time to sow Swiss chard, cukes, okra (mmm ... gumbo!), black-eyed peas, soybeans, and summer squash. Winter squash can be planted between mid-July and mid-August, while limas, bush beans, broccoli, brussels sprouts, and potatoes can be sown at any time in August.


Folks in the heart of the sunbelt—Zone 10, where frost doesn't arrive till mid-December (if it comes at all!)—can transplant peppers, eggplants, and tomatoes in July and August. Both months are fine for putting in Swiss chard, black-eyed peas, and summer squash too, but long season soybeans should be planted in July. And August is best for sowing brussels sprouts, potatoes, broccoli, and okra.

Finally, southern gardeners should know about a beautiful new book by Richard Ray and Lance Walheim, Citrus: How to Select, Grow and Enjoy. The fine large-format paperback is crammed with magnificent color photographs and detailed growing advice on over 100 varieties of familiar and unfamiliar citrus fruits, including some (like the pummelo, calamondin, and citrangequat) that most folks have never heard of!

Ofelix Salix: Rooting Hormone Catalyst

The Avant Gardener, that gold mine of horticultural information (it's available, at a cost of $15 for a year of twice-monthly issues, from Horticultural Data Processors ... and well worth the price), recently reported on the discovery of a potent root-promoting compound that comes from willow tree (genus Salix) cuttings. The substance, which is not a rooting hormone but greatly increases the effects of such products, is said to produce dramatic results. In one test, for instance, hard-to-start yellow birch cuttings failed completely when rooting was attempted with a standard 0.3% hormone treatment, but achieved 100% success when the willow extract was added to the hormone.