Every year the temperature gauge rises and gardeners head inside to cool off. The heat, when combined with humidity, affects the plants as well as the gardener. Correct placement of plants and careful watering is key to keeping them healthy in the summer.
The south is known for both humidity and heat every summer when the intense sun beats down on plants for hours each day. Many shrubs and perennials that are labeled as full sun, wilt in the brutal southern heat and do better in a location where they get some shade in the afternoon. A few perennials such as gaillardias and the delicate gaura do survive well in full sun, but even they welcome some cool afternoon shade where possible.
Knowing when to water the plants is also key to making your garden healthy and vibrant. Over watering though is known to kill more southern plants than under-watering so knowing when the plant needs moisture is crucial to their survival. Many plants and shrubs particularly those that have large leaves, or are newly planted, will show leaves that droop downward in the late morning and afternoon. This is a normal reaction to heat – the small holes on the lower side of the leaf that are used to exchange gases and moisture, close to conserve water during the day. This looks exactly like a plant that is gasping for water and when inexperienced gardeners try to alleviate the situation, they drown the roots and kill the plants. The downward curved leaves revert to normal appearance when the temperature goes down in the evening. If your hydrangea is still looking limp in the morning before the sun has risen, then you need to water, but more often the plants and shrubs will look normal and have sufficient moisture.
Garden chores of course do not cease in the heat, and some weeding will be necessary even on the hottest weeks of the summer. Time this for early in the day or late in the evening. Just as the plants wilt in the afternoon sun, so do gardeners, and over-exerting yourself can lead to serious dehydration.