Watering / Heat - Knowledgebase Question

Columbia, TN
Avatar for Tinamorse60
Question by Tinamorse60
August 12, 2007
We have impatiens hanging on our front porch, which get some sun and some shade. In this extreme heat (98+) they're not looking good at all, although we're watering regularly. Could this heat be killing them slowly? Could yellow leaves be a sign of overwatering?
Additionally...how much additional watering should be be doing on our annuals and perennials in our landscaping due to this extreme drought and heat? Every few days? More water each time?

Answer from NGA
August 12, 2007
I wish there were an easy answer to your watering question! It depends upon many factors. Plants can use more water when the weather is hot, but in addition to moisture, plant roots also need oxygen. If you keep the soil too wet, the roots can suffocate. The ideal situation is to have rich, well draining soil and to encourage deep roots so plants won't be quite so affected by summer's heat. You can do this by applying water slowly so it has a chance to fully saturated the soil to a depth of 6-8". Then wait 2-3 days after watering and dig a hole near one of the plants to see just how moist the soil is. If it is still moist 2" beneath the surface, you won't need to water for another day or two; if it is dryish, it's time to water. Experience will eventually prompt you into knowing when your flower beds need to be watered and how long you need to leave the sprinkler on. If you cover the top of he soil with a few inche of organic mulch, it will slow water evaporation, moderate soil temperatures and suppress weeds.

As for your impatiens, some are more heat tolerant than others. Sun-patiens are good examples. But for the most part, impatiens tend to wilt in the hot summer months, regardles of the amount of water they are given. You can pinch off the wilty plant parts and keep the soil moist (but not soggy wet) to keep the roots alive. As temperatures cool down the plants should regrow. Hanging baskets are difficult to keep watered in the summer's heat. I've had good luck immersing the entire basket in a larger container of water and allowing it to set for about 10 minutes, then hanging it up to drain. This completely saturates the soil and drives out any air pockets. Then I wait until the top inch of soil is dry before I water again. Immersing the baskets once every 7-10 days ensures that no air pockets or dry spots develop within the root mass.

Hope these suggestions help!

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