One of the biggest threats to your landscape during the summer months is drought stress. Although there is some relief from summer rainstorms, many plant species in the great DC and Baltimore area are currently facing drought stress.
It occurs when there is not enough water available to the roots of a plant, preventing it from thriving and proceeding with its normal cycles. The shortage of water may be due to lack of rain, no irrigation, transpiration or evaporation in the atmosphere, periods of high temperatures, intense lighting, etc.
In essence, drought stress is severe dehydration of a plant. In response, plants will halt growth and reduce photosynthesis. This happens each summer in most regions and typically peaks in August. The plants that are most sensitive to drought will begin having symptoms as soon as early or mid-July.
Drought stress happens at different speeds for different species depending on numerous factors. Young plants can have limited root systems that make them vulnerable to drought stress. On the other hand, series of plants placed close to each other may be sensitive to drought stress due to competing root systems. Plants whose foliage are much greater than their root systems will become dehydrated before plants with less leaves, as the roots are trying to hydrate the entire plant. The water-holding capacity of the soil is another factor. Plants in clay soils will be less susceptible to drought stress than plants growing in sandy soils, because clay has a higher water-holding capacity.
Just as the cause of drought stress differs from one plant species to the next, symptoms vary.
Common characteristics of plants facing drought stress include color change, usually with a loss of vibrancy. For example, bright blue Hydrangeas will turn to a “bleached” yellow or off-white shade. Turf grass will change from a strong green to yellow or dull/grey-ish shade of green (You may notice the green fading throughout the baseball field to the right). For trees, the change in color is usually from green to yellow. These color transformations are typically recognized as the first stage of drought stress, indicating that the plant is entering dormancy.
Another beginning characteristic of drought stress is wilting foliage. A plant with leaves that remain wilted overnight is likely to die if not properly irrigated.
Symptoms may be either acute or chronic. The scorching of leaves/color change and wilting foliage are examples of acute characteristics. They are easy to notice and treat if done so promptly. Chronic symptoms of drought are a bit harder to recognize. Examples are reduced leaf size, leaf spotting, dieback of stems, cracking bark, bleeding trunk, slow plant growth etc.
Plants with acute symptoms can act as a warning system for all surrounding plants when there is an onset of drought stress. Indicator plants are the the most drought sensitive and the first to show symptoms. One of the best ways to prevent drought stress is to pay attention to indicator plants on your property.
A few common examples include: Doublefile viburnum, azaleas, dogwoods, forsythia, Japanese maple, redbud, hydrangea
We will dig into one of the most common and beloved indicator plants in our area as an example – Hydrangeas. Their bushes grow to massive sizes, along with huge vibrant flowers, but this appearance becomes fragile and threatened in the summer months. Compared to most shrubs, their drought tolerance is extremely low. The name Hydrangea comes from the Greek word for water, “hydor,” representing the nature of the plant.
Although Hydrangeas have their challenges during the warm season, they are helpful to have on your property, since they do a wonderful job of speaking for their surrounding plants. As soon as your Hydrangeas show symptoms of drought stress, you know it is time to quickly water not only them, but all the plants on your property. In fact, many people want Hydrangeas on their property for this reason alone.
If you want to be sure your Hydrangeas are not pushed to the limit, the general rule of thumb is to place them in a spot that receives shade each day, not direct sunlight. All types of hydrangeas are more likely to thrive if they are shaded for at least part, or even most of the day. Also, this approach will not keep them from doing their indicator work for you! When suffering from drought stress, their leaves will become less vibrant, and their flowers may become a significantly different color. It is normal for their foliage to wilt in the heat of the afternoon, but if the leaves remain wilted, prompt irrigation is needed.
Interestingly, many plants have died out due to drought intolerance and others have evolved to become more resistant to drought. This involves different tactics depending on the species, but one of the strongest is maintaining cell homeostasis in times of water deficiency.
We can offer plants on our landscapes a bit of help by being proactive. Of course watering/a good irrigation system is the best response, but getting ahead of it is the tricky part. Our crews strive to address the details before properties are damaged by drought stress, not after. In addition to paying attention to indicator plants, we control weeds and grasses that surround trees or ornamental plants. This can help with drought stress, by lowering competition for water among the plants’ roots.
The greater DC and Baltimore area annually faces drought stress in the summer months. This July 2021 heat is surely putting many properties at risk of drought stress.
Although issue of drought stress is oftentimes inevitable, there are numerous ways to design your landscape so that it is prepared to put up the fight. Options include irrigation systems, mulching, proper placement of plant species and choosing plants that are drought tolerant for the summer months.
And if you are noticing the cues from any indicator plants on your property or want to be sure your landscape is not at risk, be sure to contact us!