Growing Dahlias in the Heat
People are often puzzled to learn that all dahlias aren’t naturals for hot regions. “Wait, didn't these plants originate in Mexico?” Yes, that’s correct. However, dahlias come from high elevation mountain plateaus where the days are hots and the nights are cool. Dahlias appreciate those cool evenings.
If you’re smitten with dahlias (and who isn’t) here are suggestions for having happier dahlias if you garden in a region where summers are hot. While we can't guarantee great results, the following should improve the odds.
Tips for Growing Dahlias in the Heat
1. Choose varieties that have demonstrated an ability to perform well in hot areas. The Dahlia Society of Georgia has created good information on varieties and growing techniques. Find our recommended varieties here
2. Amend your soil to incorporate lots of organic matter; leaf mold, aged horse or chicken manure, or Black Kow brand bagged aged manure. This improves both soil fertility and drainage.
3. Plant in spring about the time when tomatoes are planted in your region. Typically, February through April are good months, dependiing on your location. After that temperatures tend to be too warm for plants that are just settling in.
4. Keep the plants’ roots cool by adding a 2-3” layer of mulch. Avoid having the mulch rest against the stalks as that can trap moisture and encourage stem rot.
5. Keep the plants cool by giving them a quick shower in the afternoon. This helps get dahlias through the hottest part of the day.
6. Consider using shade cloth or patio umbrellas to provide shade during the hottest parts of the day. Or grow your dahlias where they’ll enjoy light afternoon shade from trees or buildings.
7. Recognize that during the hottest part of the summer the plants may stall and not produce many/any flowers. Flower forms can change slightly, too, when temperatures really heat up, producing blooms that are more open and flatter. (Think of the accessable pollen as a short term gift to your local pollinator community.) Keep an eye out for leaf wilt which may signal that your plants aren’t getting enough water to balance the amount being lost through leaf evaporation. Usually, deep watering twice or three times a week is sufficient.
When the weather cools, dahlias perk up and burst into action developing buds and blooms. And your patience pays off!