St. Augustine is touted as a drought-tolerant, low-maintenance, luscious turf grass for the Southeast. But, it’s only luscious if it’s well maintained, and in order to be well-maintained, it has to be watered regularly. So, even if St. Augustine was drought tolerant, would it look good if it was water-stressed?
Drought tolerance has much more to do with maintenance practices than it does with plant biology. Tolerance is far from thriving. A lawn may tolerate water stress, but it will tolerate it much better with healthy soil and regular mowing. Poor soil conditions, pests, diseases, and weeds can destroy any chance a turf has at surviving drought conditions, even if it is drought tolerant.
So, is St. Augustine grass drought tolerant? Yes, provided you follow proper maintenance practices and continue to improve your soil. However, drought tolerance does not mean drought resistance, so St. Augustine will still need deep, infrequent irrigation.
What Is Drought Tolerance?
Not even scientists can agree on what makes a plant drought tolerant. There are many different genetic traits that work together to allow a plant to weather times of water stress.
The general definition of drought tolerance is the degree to which a plant is adapted to arid or drought conditions (source).
Drought-tolerant plants are able to do the following during times of stress:
Turgidity refers to the water pressure within a plant’s cells. High turgidity results in a firm, rigid plant material. Low turgidity results in wilting, or a drop in pressure.
During times of regular irrigation, grass will have high turgidity, which keeps it upright. As water evaporates from the soil, the grass loses turgidity and wilts. A drought-tolerant grass has several reactions to water stress that allow it to keep turgidity with low water content.
A plant can reduce the size of a cell to maintain pressure, and close up the stomata in the leaf to prevent transpiration. Once a plant slows the release of water, it also slows down the ability to photosynthesize. In essence, the plant stops putting water and energy into active growth and enters survival mode.
As plants become more established, they are able to tolerate drought conditions for longer. As the roots grow deeper, plants are even able to continue to grow and reproduce without an entire season of water.
Grow More Roots
Deep roots allow a plant to take up more water, so some plants react to drought stress by growing a deeper web to access moisture far beneath the surface. St. Augustine roots can grow over a foot deep in good conditions, but they can send roots much deeper and wider under drought conditions.
However, grass will only grow deeper if you follow a deep, infrequent watering schedule. Daily irrigation for less than an hour will create shallow surface roots that will severely restrict your lawn’s ability to thrive for long without water.
How To Manage St. Augustine In Drought Conditions
Drought-tolerant grasses don’t magically survive in 110o F temperatures and 3’ of sand. They still require consistent maintenance in order to thrive during periods of water stress.
If you live in an area of the Southeast with water restrictions, you will have to tailor your maintenance schedule for drought conditions. This will mean a strategic irrigation schedule, consistent mowing, weed management, and building a healthy soil profile.
You can increase the drought tolerance of your lawn by encouraging deep root growth. Encourage roots to grow deeper by watering once per week for a few hours so the water will penetrate deep into the soil. Throughout the week, as the grass gets water-stressed, it will grow towards the available water below the surface.
As you continue to irrigate deep and infrequent, the roots will grow deeper and stronger. Then, if you do encounter drought conditions, the roots will be deep enough to pull water from a few feet below the surface.
Consistent mowing at the correct height will help increase drought tolerance. The key to surviving drought conditions are deep roots, and one of the best ways to encourage deep root growth is to mow.
Why? Mowing is a stress trigger, and stress makes plants prepare for survival. The primary response is to grow new, deeper roots, meaning consistent mowing will signal your grass to keep growing down towards the water, even if it’s irrigated regularly. The best mowing height for St. Augustine is 2.5” – 4”.
Be sure to read Can You Dethatch St. Augustine Grass?
Broad-leaf weeds are water hogs. Their large leaves mean they have higher water needs than grass, meaning during a drought, the weeds will absorb any available water before your turf can get to it.
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For weeds, the best offense is a good defense. Protect the health of your turf so it can fill in bare patches of soil and choke out herbaceous weeds. If you have poor soil, weeds will thrive, so continuing to build up your soil will deter many weeds from taking root. If you have too many weeds to manage naturally, use a broad-leaf herbicide to get them under control, and then keep them at bay with good management practices.
If you live in an area with consistent dry periods, chances are you have a poor soil profile. If your soil isn’t able to hold water or nutrients in a way that your grass can access, it will suffer during drought conditions even if it’s considered drought tolerant.
Regardless of your current soil texture, topdressing with compost twice per year will build up the soil and help with water retention. It will improve the water-holding capacity of sandy soils, and loosen clay soils so roots can penetrate deeper.
Recognizing Drought Stress In St. Augustine Grass
Drought stress looks similar in most turf grasses, so it’s easy to recognize once you know what to look for.
The key characteristics of drought stress are footprints and a darker color. If you walk across your lawn and it leaves a shoe imprint (or toes if you like to live on the edge), then your grass is officially in the early stages of drought stress.
This is actually a healthy stage for your lawn, because it is during this time that the roots grow deeper, and your lawn gets tougher. This is usually the stage when you would irrigate (3/4”-1”), and mow a few days later. A cycle of irrigation, mowing, and early drought stress will create a resilient lawn. St. Augustine is able to go a few weeks to a few months without water before showing drought stress.
Severe drought stress will cause your lawn to go into survival mode. This can mean your grass stops growing, thins out, and possibly goes dormant to conserve water. Although it’s not the lush, green lawn you may have hoped for, this is technically another aspect of drought resistance. Going dormant is one of the final safety precautions as a grass cuts down on water needs.
As soon as the turf is irrigated, it should green up and begin growing again. Avoid the urge to fertilize to encourage green growth. Heavy doses of nitrogen during drought stress will provide short-term growth followed by long-term stress. It’s better to let your lawn acclimate to normal watering before forcing large energy outputs due to fertilizers.
St. Augustine is a beautiful turf option for the Southeastern part of the United States. It is aggressive, resilient, and tolerant of a wide range of adverse conditions. With proper management, it can weather very difficult environments.
For more information on establishing a St. Augustine lawn, check out our other articles on warm-season grasses and preparing for new turfgrass.
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