A few vegetables enjoy the searing heat, likewise, some annuals and perennials. When a hot-spell continues throughout the summer, though, we’re all cooked, even with adequate watering, for water is expensive and increased humidity brings fungal invasions. And most heat-loving plants have their upper limits.
Sunflowers are the exception. North Dakota State University’s Agricultural Weather Network says that the common sunflower (Helianthus annuus L.) will stop growing when readings drop below 44 degrees Fahrenheit but continue to prosper despite climbing temperatures.

Heated veggies
Along with sunflowers, eggplant, gourds, melons, okra and sweet potatoes thrive in 70- to 85-degree Fahrenheit daytime temps with nighttimes above 60.
However, Colorado State University tells us that when temperatures rise above 90 by midmorning, fruit-set is “significantly reduced.” Fewer melon flowers develop and fruit drops prematurely.
Regardless, during hot, dry patches all will need moist soil with 2 to 3 inches of organic mulch and periodic watering. Do not use black landscape fabric on very hot days because it will certainly cook the earth below.

Burning Blossoms
Drought-tolerant does not mean heat-resistant. Many high-desert plants need chilly, dry evenings. Some tropicals, comfortable in steamy jungles, must rest within the shade, awakening at dawn with a cool breeze. Plants of the arid coastal hills readily sop-up their daily dose of dank heavy fog until the morning sun burns off the residue.
Consider these brave few, these fire-breathing annuals that easily embrace day and night extremes—no relief needed. They’ll not melt into a fungal fuzz with Virginia’s hazy humidity: amaranthus, four-o’clocks, gaillardia, globe amaranth (Gomphrena globosa), morning glory, ornamental pepper, portulaca, salvia, torenia and zinnia. Neither will they wilt or curl as others collapse.
Though I cannot list them all, note perennials that meet the fevered air with stems and dignity intact share these vital cooling, water-storage traits: thick waxy leaves shielding against the scald, conserving moisture—sedums and Agave; feathery foliage, slivery hairs, minimizing evaporation, maximizing air movement—yarrow and lamb’s ear; hefty taproots hoarding water, shady, ground-hugging vines—gaura and ornamental sweet potato.

Seething Shrubs
Brooms (not invasive in Virginia), cotoneaster, juniper, rugosa rose, yew—this modest inventory of woody ornamentals will stand up well to the dog days of Virginia. They protect themselves with the same tricks as the perennials: thick waxy leaves, deep, tortuous taproots, and filigreed airy architecture.

Blazing Bulbs
Corms, rhizomes and tubers, too. Talk about protection—these are the ultimate subterranean heat deflectors. Hardy bulbs left in the ground year-round prefer your garden’s bright scorched niches and include crocosmia, iris and peony. But dahlias along with other tender “bulbs” will need afternoon shade to survive any 90-degree plus stretches; and like all that are not hardy for zone 6, must be lifted at the first light frost.

Caution
Defensive gardening has its downside. During those rare cool and rainy summers, lighten or even clear away thick mulch where fungi and rot may come to life, then widen the narrow spaces between plants to promote airflow. You’re ready.

TIP OF THE WEEK
Carry a quarter-filled bucket of water when setting-out to cull flowers and culinary herbs. Use sharp shears to make the initial horizontal cut, then a slant slice under water as you arrange the blooms in a vase. Loosely wrap the herbs in wax paper; store in the refrigerator’s vegetable keeper.