As temperatures rise, some annuals slow down or stop flowering due to heat stall. They will recover as temperatures cool but may leave your gardens or containers looking less colorful.
Take some time now to evaluate annual flowers that are thriving in your garden and those that may need to be left off the plant list for next year’s garden.
Start looking for more heat-tolerant plants and cultivars to use in the future. A visit to your local botanic garden and viewing gardens in your neighborhood can help provide insight and inspirations for plants suited to your summer weather.
Zinnias are known for their heat and drought tolerance. These long-blooming annuals come in a variety of colors and heights. Wheat, plume, and crested celosia not only add color, but also interesting flower shapes to gardens and arrangements.
Angelonias, also known as summer snapdragons, are upright plants that make great vertical accents and add season-long color to containers and gardens. Granvia strawflowers are taller, more vigorous plants with larger flowers than older strawflower varieties. Enjoy them in the garden and for months after in arrangements, dried wreaths, and other decorations.
Annual vinca, Catharanthus, with its shiny leaves and long-lasting flowers, thrives in hot, dry weather. The dainty flowers of the Soiree® Kawaii series and the fringed, ruffled flower petals of the Soiree® Flemenco series provide a unique flare. Include pentas with their star-shaped flowers to help attract and support butterflies. You’ll find plants with white, red, pink, lavender, violet, and bicolor flowers, and even a few trailing varieties.
Cupheas are not only heat tolerant but are magnets for hummingbirds. These season-long bloomers are covered with flowers and do not need deadheading. Mandevilla is another long-blooming, heat-tolerant plant that thrives in sunny locations. You’ll find upright, trailing, and tall climbing varieties to include in gardens, containers, and hanging baskets.
If you are looking for a heat-tolerant, trailing plant, consider bidens. The BeeDance® series is an earlier and continuous flowering variety. Moss roses and other portulacas are also trailing and low-growing plants that can be used as annual groundcovers, edging plants, and trailers in containers.
Look for more heat-tolerant cultivars of your favorite annuals that tend to stop blooming during hot weather. Heatopia™, Hot® Waterblue, Techno®, and Laguna® lobelias show more heat tolerance than many older lobelia cultivars. White Stream™, Snow Princess®, and Frosty Knight® are a few alyssum cultivars to consider. They tolerate the heat but prefer moist well-drained soil.
Hot Pak™ French marigolds have been bred for increased hot weather tolerance. The triploid marigolds like Endurance™ and Zenith™ are a cross between the African and French marigolds. They have the longer bloom time of the French marigold and the heat tolerance of the African species.
Don’t give up on heat stalled annual plants in your garden and containers. Continue to water the heat-stressed plants as needed but wait for them to recover before fertilizing if needed. Trim back leggy plants and once the temperatures cool, the plants will start flowering.
Continue to watch for, try, and evaluate new, more heat-tolerant additions for your gardens and containers. Finding the right plants for your growing conditions and garden design can help boost your garden’s beauty and your enjoyment even as temperatures rise.
Melinda Myers has written more than 20 gardening books, including the Midwest Gardener’s Handbook, 2nd Edition and Small Space Gardening. She hosts The Great Courses “How to Grow Anything” instant video series and the nationally syndicated Melinda’s Garden Moment radio program. Myers is a columnist and contributing editor for Birds & Blooms magazine and her website is www.MelindaMyers.com.