Landscape, Defend Thyself!

Mark Peterson

Plants have developed unique characteristics to help them beat the heat and many other extremes. Sometimes the best thing you can do is simply walk away and let them fend for themselves.

Plants, as far as I know, don’t have nerves or organs that require cooling like humans. In fact, some plants can tolerate — even prefer — triple digit temperatures.

So I find it quite amusing when I hear all sorts of moaning and groaning about plants suffering in this heat, desperate for water, dying of thirst.

As a rule, plants do not fight the heat so much as the combination of high lumens, high winds, low humidity and low soil moisture. In most cases, plants have the ability to withstand high temperatures as well as the other evapotranspiration or ET factors, including: sunlight, wind, relative humidity and evaporation.

ET is the combination of total water used by the plant, water that evaporates from the leaves (transpiration) and water that evaporates from ground.

In response to weather extremes, plants have developed unique characteristics to combat high ET. Examples of these characteristics include heavy wax coatings to prevent water loss, tiny hairs on the undersides of leaves to prevent evaporation by wind, and continued photosynthesis even with access to carbon dioxide restricted. Sometimes it’s as simple as going dormant until the weather passes, and no amount of water will arouse it. Brown does not mean dead.

While ET varies among plants, the actual water used by a plant is seldom more than 5 percent of the total water absorbed by the roots. The remaining 95 percent is lost to the air. Some plants can tolerate very high ET — yucca or ashe juniper actually continue to grow. Others, like St. Augustine for example, quickly go dormant under high ET.

And then there are some plants that truly prefer high temperatures. Bermuda grass does best when temperatures reach 100 degrees, while Pride of Barbados, firebush and damianita don’t even reach their peak until temps are in the high 90s.

Here is the really cool part about ET: The changing of liquid water to water vapor as it escapes from the leaves actually COOLS the plants. It takes a lot energy to transform from one state to another and that is pulled from the atmosphere around the leaf.

In other words, trust your plants and their abilities. Water deeply, but infrequently. Realize that leaves, grass clippings and compost are nature’s best fertilizer. And, sometimes on those occasions, the best care for plants may be for humans to simply walk away from them.

Start typing and press Enter to search