7 Perennials to Beat the Summer Heat
Learn about various perennials to beat the Oklahoma summer heat
Bright Eyes Phlox | Photo by Dee Nash
It’s August in Oklahoma, and that means heat—the kind most gardeners fear. But, fear not my friends. Here are seven perennials to beat summer heat. Not only are these plants sun lovers, because they are perennial, they return to your garden every year.
Black-eyed Susans, Rudbeckia hirta or R. fulgida. Black-eyed Susans are a genus of plants in the sunflower family. Some varieties are short-lived perennials, but do reseed. As with many prairie natives, rudbeckias like their soil lean, meaning no added fertilizer. Compost is okay for better drainage and water retention though.
‘Goldsturm,’ R. fulgida var. sullivantii is truly perennial and spreads via underground stems.
If you want to grow another seed variety, you have dozens from which to choose. For best results, start seeds indoors in early March and transplant after the last freeze instead of buying plants already blooming in summer. Some varieties to try from seed are ‘Cherokee Sunset,’ ‘Indian Summer,’ ‘Irish Eyes’ and ‘Prairie Sun,’ a bicolor with a light green cone. R. subtomentosa ‘Henry Eilers’ is a tall and beautiful quilled variety of sweet coneflower.
Two key diseases plague black-eyed Susans: septoria leaf spot and aster yellows. Avoid overcrowding and overhead watering. Also, remove and destroy any plants with oddly shaped flowers.
Joe pye weed, Eutrochium purpureum, another prairie native, is easy to grow. Most varieties are tall plants so place them at the back of the border, or grow a dwarf selection like ‘Baby Joe’ or ‘Little Joe.’
Shasta daisies, Leucanthemum × superbum, are bright and cheerful. Planted en mass they make a huge statement in the summer garden. The best cultivars are ‘Becky,’ the 2003 Perennial Plant of the Year, and ‘Banana Cream,’ which has lemon yellow flowers that fade to white. Both varieties are compact and don’t flop like ‘Alaska.’
Summer phlox, Phlox paniculata, blooms for months during the hottest time of the year. Newer varieties like ‘Bright Eyes,’ ‘John Fanick,’ and ‘Cherry Cream’ are powdery mildew resistant. ‘Jeana’ is a new variety with smaller florets and loads of nectar. If you like butterflies, grow summer phlox for the winged adults.
Bee balm, Monarda didyma, is part of the mint family, so it spreads via underground stems. It is garden worthy, but also a bully so you’ll need to keep it from overpowering other perennials. Look for newer varieties that are more resistant to powdery mildew like ‘Jacob Cline.’ Bee balms attract hummingbirds and bees. Deer don’t like them either. ‘Pink Lace’ is a dwarf variety.
Cup plant, Silphium perfoliatum, is a tall plant native throughout much of the middle and eastern U.S. with bright yellow flowers. The leaves form a small cup at the base of the stem that collects rainwater. Bees and butterflies love it. If you grow cup plant, it doesn’t need much water once established, but it does need room to grow. Put it at the back of the border with Joe pye weed.
Beardtongue, Penstemon, flowers in late spring and early summer. Favorite varieties are ‘Dark Towers’ (pink flowers) and ‘Midnight Masquerade’ (purple blooms). Both varieties have dark leaves providing depth to the sunny border.
I didn’t mention salvias, but they are a wonderful genus of sun-loving perennials too.
These heat-busting perennials are all tested in my own garden, and I assure you they grow well there. Even though they don’t mind heat, they are living plants so you do need to water them. Try for an inch a week. In my own garden, I use drip irrigation to conserve water and put it at the plant’s roots. Also, since most are prairie natives or selections of such, plant them in full sun for best results.