How to Care for Your Perennials during a Sizzling!!! Summer
The most important task in keeping your perennials healthy in summer is to regularly check them for stress. Stress in summer usually arises from too much heat and too little water. Common signs of stress are:
· Tender leaves wilt from exposure to too much heat.
· Foliage turns pale after it was once bright green. For example, the green leaves of my potted begonia looked almost bleached after several days of intense sunlight and ninety-degree temperatures.
· The edges of leaves have brown or yellow spots or there are dots or yellow speckles on the surface of the leaves. These spots or speckles are a sign of sunburn. On a recent hot afternoon, I was surprised to see the edges of a few leaves on my native azalea had small brown patches even though I had been watering the azalea, and the plant was in partial shade.
· Flowers and/or leaves are dropping off or turning yellow.
· A plant which has begun to flower has smaller blooms than usual. This sign of stress, I saw on my Shasta Daisies. There were lots of blooms, but they were clearly smaller than the blooms of the previous year.
Once you notice stress it is important to try to reduce stress by watering the plant more and at the right time of day (which would be early in the morning or late afternoon shortly before the sun sets). Another way to reduce stress is to make sure the plant is well mulched. Lastly, a screen for shade for the brightest party of the day may help the plant survive. I have used plastic toy crates that have open cross hatch sides to screen some of the sunlight from small, sensitive plants.
We all know that the amount of watering needed during the summer for perennials depends on the type of plant you have and its location. Below are some examples of perennials tolerant of bright sun and/or dry conditions.
Dry Tolerant: Penstemon, Echinacea (Cone Flower), Yarrow, False Indigo, Perennial Salvia, Black-Eyed Susan, and Amsonia.
Sun Tolerant: Echinacea (Cone Flower), Monarda (Bee Balm), Sedums including Ice Plant, Lavender, Salvias, Verbena, Aster, Shasta Daisy, Butterfly Weed, Blanket Flower, Coreopsis, Queen Ann’s Lace, Speedwell and Hardy Chrysanthemums.
Other ways you can help your perennials during a heat wave is to refrain from fertilizing your plants, re-potting them or pruning them.
Fertilization: Although fertilization is important for growing plants, a stressed plant should never be fertilized until it recovers. If your plant is stressed, you should consider that it is in survivor mode. Therefore, it is not prepared to make use of a fertilizer’s nutrients.
Re-potting: A period of ninety-degree weather is not a good time to re-pot either a new plant, a plant that is outgrowing its container, or any plant. Leaves and roots may be damaged during re-potting. The plant needs the best conditions for repair, and to become accustomed to its new home.
Pruning: While a little pruning may eliminate wilting or discolored leaves or spur new growth, it is not the best action to take. For instance, a slightly discolored leaf might rebound when temperatures and moisture conditions return to normal. Stress damaged leaves might still be supporting the overall health of the plant until it fully recovers. Additionally, pruning alone adds a bit of stress to your plant.
Below are a few tips for keeping perennials in top form in the summer (even if they are not showing signs of stress).
Staking: Taller perennials such as Delphiniums, Hollyhocks, and Peonies will probably need to be staked due to their summer growth pattern. You can stake single stems by inserting a rod or sturdy stick into the ground and tying the stem to it. Clump-forming plants with multiple stems may be grown through a hoop.
Deadheading and Disbudding: Deadheading means cutting the faded flowers off your plants. It helps keep your perennials healthy and looking their best for the whole summer. Many perennials respond to deadheading by putting out more blooms such as Daisies, Phlox, Veronica, Yarrow, and Coreopsis. If you do not want seed spreading a perennial to other parts of your garden, deadheading will solve that problem. If you want to save the seeds, you can refrain from deadheading completely or deadhead only a portion of your plant or plants. You can disbud a plant, if you want to encourage big flowers rather than many small ones. To disbud, remove all but one or two flower buds on each stem, before the buds start to open. The plant then directs all its energy to the remaining buds, resulting in larger flowers. Gardeners often disbud Dahlias, Carnations, Peonies and Chrysanthemums.
Pinching: Pinching increases the fullness of a plant (more stems and leaves) and controls height. To pinch just snip or pinch off the top few inches (about 4 inches) of the plant when it grows to a foot tall in spring and then again in the middle of summer. Each stem you cut grows several new stems. The result is stocky sprays of more, but smaller flowers. Chrysanthemums and Asters are two perennials that are routinely pinched. Do not pinch chrysanthemum shoots after July 15. If you prune them after that time, you may eliminate some flower buds and delay the blooming of those that remain. Shoots that are not pinched may grow tall and spindly. Flowers on those plants tend to be top-heavy. Tall mums also block sunlight from their lower parts, causing fewer leaves and the lower leaves to die.
In the summer, a disease common to perennials is powdery mildew. Powdery mildew is often seen on Asters, Bee Balm, Black-eyed Susan, Columbine, Coreopsis, Phlox and Salvias. It looks like a white or gray fuzzy growth on the leaves. This is the result of fungi which grow well in high humidity and warm temperatures. To keep the humidity around the plant low, water perennials in the morning and use a soaker hose instead of a sprinkler or at least try to water without wetting the leaves. Remember that poor air circulation, overcrowded plants, insufficient light and over-fertilization are also conditions that will increase the growth of these fungi.
Perennials are a marvelous group of plants valued for their longevity and variety. With care, they can bring many years of enjoyment in your garden. Hopefully, with the above tips your perennials will flourish during the hot Georgia summer season.
Holly Sparrow, Headwaters Master Gardener