Drought-proofing Your Annuals

The drought in Texas is continuing as they approach 60 days of triple digit temperatures so far this year.  A heatwave finally descends on the Northeast United States after a colder and rainer summer. Will the weather ever cooperate again? Seems that the garden is having a tougher time than ever before. And annuals are one of the first to feel the brunt of hot and dry weather.

Dealing with drought doesn't mean resorting to all drought resistant succulent plants as seen here at the Idea Garden at Longwood Gardens, Kennett Square, PA.

Dealing with drought doesn't mean resorting to all drought resistant succulent plants as seen here at the Idea Garden at Longwood Gardens, Kennett Square, PA.

Annuals in beds and containers are the first plants to show signs of stress from lack of water. Newly planted annuals have very small root systems that are poorly suited for the task of reaching out in search of water. When planting, annuals still need to be given additional water even if their roots were wet. The surrounding soil, if dry, will quickly wick away the moisture from the plant roots leaving them dry.

The first signs of distress are flowers buds falling off or flowers fading faster than usual. As the drought conditions become more severe, the leaves will be affected next. This could be visible by wilting, “flagging”, or rolling of the leaves (starting with the older, then the younger).

Begonias will react to drought by changing the colour and glossiness of their leaves. The leaves will become shinier and turn a dull grey-green. Other annuals will have a dull look to their foliage. Plants under extreme water stress will turn yellow, collapse, and then die. Petunias, begonias, impatiens, fuchsia, coleus, and nicotiana will show signs of water stress first.


A full, lush hanging basket, part of the streetscape in Niagara-on-the-Lake, Ontario Canada.

A full, lush hanging basket, part of the streetscape in Niagara-on-the-Lake, Ontario Canada.

Geraniums, dusty miller, portulaca, helichrysum, and salvia will tolerate more drought. Each type of plant has its own “point of no return” after which they cannot be revived due to permanent damage. Give them water before they reach this point. The appropriate time to water is when the soil is dry to a depth of 2.5 cm/1 inch (for newly planted annuals) or 5-7 cm/2-3 inches (for established annuals) depending on their root depth. Do not wait until plants have started to wilt before watering! Check the soil moisture level with the traditional “finger” test and then water when appropriate. A sandy soil dries out more rapidly than a heavy clay one and an organic-free soil holds less water than an organic rich one. Windy days will cause plants and soils to loose more moisture faster than on calm days. Wind will also blow water from its intended target. In this case, irrigation will have to be used for longer periods to apply the same amount of water as a calm day.

Annuals in containers are more susceptible to moisture stress because of the small area for roots to grow. They are also at risk because of the relatively small amount of water stored in that small amount of soil. Many annuals will tolerate potting soils with water holding products incorporated into them. This really works and increases the duration between watering. Many container soils that are peat moss based are very hard to re-moisten if they become extremely dry. Water applied will run through quite quickly and out the bottom of the container. Keep applying water to the container several times until it saturates into the soil and hope that your rain dance will work soon.

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