Extension Notebook: Sultry plants to beat the heat

Summer can be a scorcher, but if you select the right plants, they can look sizzling all summer long. Trial plants are evaluated throughout the season for heat tolerance and can be planted in the ground or in containers.

We can learn from the previous seasons what worked well and what didn’t. Expectations of what plants can endure the heat of summer can be satisfied with the research of others.

Native plants are known to be tolerant of the heat we have in Illinois over the summer. Changes of the seasons as the years go by influence what can potentially be grown in Illinois, as we’ve seen with the USDA hardiness zone map recent update.

Some plants may start out spectacular but fade and whither under the intense heat, so be cautious in your site selection. The American Horticulture Society Heat Zone Map is often neglected when it comes to plant selection. Plants that have similar watering needs will be easier to manage. Irrigation also varies as the amount of rainfall fluctuates.

Mulching plants is also an option to conserve moisture, especially when the soil is dry. Mulch must be kept at a distance from the crowns of woody plants. Apply a 2-inch layer

Location can influence the temperature in the garden. Areas near hardscapes are generally warmer. Wind also adds to the dryness of a site.

Adding shade structures can help modify the conditions and assist with some plants.

Be sure to research the requirements and culture of the plants you choose to grow.

Here are some cultivars to beat the heat this summer:

• Verbena tended to melt with the heat, but Verbena “Superbena Sparkling Amethyst Improved” is an improvement on the number of blooms present in the summer compared to previous cultivars.

• Zinnia “Double Zahara Fire” performs best in full sun and thrives in the summer heat.

• Titan series of vincas is outstanding in hot and dry conditions.

• Ornamental onions or the Allium spp. vary in bloom times and height, but the Persian alliums can be the showstoppers in the summer with their large heads.

• Arkansas Bluestar (Amsonia hubrichtii) has star-shaped blooms in the summer and excellent fall color is well adapted to summer heat and humidity.

• Catmint (Nepeta x faassenii; N. racemosa) is durable in the heat once established and drought tolerant.

• Russian Sage (Perovskia atriplicifolia) is best planted in the spring once the soils are warm.

• Salvia “May Night” thrives in hot, sunny locations. Plants may rebloom with some encouragement with watering during dry periods.

• Little Blue Stem (Schizachyrium scoparium) “The Blues” is one of the most offered cultivars. Combines well with other plants suited for dry conditions.

• “Autumn Fire” and “Autumn Joy” sedum are wonderful bloomers in the summer. Prefer full sun, will survive in partial shade.

• Goldenrod (Solidago spp.) “Fireworks” Goldenrod does best with regular moisture.

For more information on plants for hot areas, connect with your local Illinois Extension county office at go.illinois.edu/ExtensionOffice.

Andrew Holsinger is a University of Illinois Extension horticulture educator serving Christian, Jersey, Macoupin and Montgomery counties.