Tips on keeping crops cool during hot weather. Hot summer sun can be hard on garden plants and their roots. If watering and mulching are not doing enough to keep your plants cool enough to continue producing, consider shading the plants or at least their roots. Late summer also is the time to plant your fall-producing crops, such as spinach, lettuce, broccoli, carrots, beets and radishes.
Learn about keeping crops cool during hot weather, how to protect your crops from ol’ sol’s relentless radiation, plus simple late summer techniques for a bountiful fall harvest.
Keeping Crops Cool During Hot Weather
If you want to keep your garden productive well into fall, then late summer is a busy season that must be embraced. Hot temperatures are as rough on plants as on the gardeners who grow them, but here’s a roundup of techniques you can use to help you and your crops cope. And the sweat you invest when you seed beets or transplant broccoli will be richly rewarded in a few short weeks. The late summer planting list is a long one with plenty of choices — chard, spinach, lettuce, kale, broccoli, kohlrabi, carrots, beets, radishes and turnips. Now is the time to give cool-season vegetables a second run in your garden.
Sizzlin’ Summer: Preventing Heat Stress in Plants
At this point you may be thinking it’s all you can do to nurse tomatoes and other pet crops through a mean summer. We know your pain! But even if you keep the soil evenly moist by using lots of soakers or drip irrigation hoses covered with a thick mulch, many vegetables will abort their blossoms rather than set fruit in extreme heat. Temperatures in the 90s cause many beans to hold back flowers, and tomatoes, peppers and eggplants start having trouble completing the pollination process when temperatures rise above only 86 degrees Fahrenheit.
Commercial growers often use sprinkling to cool plants down. A late afternoon sprinkling may be an excellent idea, but strategically placed shading devices are often more practical, more water efficient and much less time-consuming. For example, you can easily cool down the sunny sides of tomatoes by installing a short run of snow fencing or pre-assembled sections of picket fence along the south or west side of the row.
Shade covers made from lightweight cloth (such as old sheets) also will help keep struggling plants cool, though they must be held several inches above the plants to keep them from retaining heat. When using a cloth-type shade cover over plants, tie or staple the corners to wood stakes. You can probably buy shade cloth at your garden center, or a 6-by-12-foot piece that blocks 50 percent of light is available for $17.50 from Lee Valley Tools. Scavenge before you buy. Old window screens make good shade covers, too, as do narrow panels of wood lattice. If plants are so tall that installing a shade cover over them is impractical, simply situate a sun screen alongside them to shield their bases from afternoon sun.
Controlled shade also may help you grow lettuce and other leafy greens despite 90-degree heat. In a 2001 study conducted on two Kansas City-area organic farms and at the Kansas State Research and Extension Center in Olathe, high tunnels covered with 40 percent shade cloth doubled the survival of transplanted lettuce seedlings and kept the plants from developing bitter flavors. You can learn more about high tunnel culture, hosted by Kansas State University.