When a drought hits, some plants stand strong while others wither and die. Ever wondered what makes a plant drought tolerant? It comes down to adaptations that plants developed over millions of years to survive in dry environments. Deep roots, waxy leaves, and early leaf drop are just some of the ways that drought-tolerant plants defeat the dry weather.
Let’s take a closer look at what “drought tolerant” means, the specific features and benefits of drought-tolerant plants, and which ones you should consider for your drought-prone or water-wise lawn.
What does drought tolerant mean?
Drought-tolerant plants can withstand a few weeks to a month of drought with no supplemental water. So, if you go on a two-week vacation just as a drought arrives, you won’t have to sit at the hotel and worry about returning to a plant infirmary (or worse, cemetery). Drought-tolerant plants won’t wither and die as soon as a dry spell hits.
While drought-tolerant plants can survive for a short period without water, drought-resistant plants are the heavy hitters. Some can survive for years without any supplemental water, while drought-tolerant plants need a good soaking if a dry period extends beyond a month.
All drought-resistant plants are drought-tolerant, but not all drought-tolerant plants are drought-resistant. So, for our purposes, when we talk about drought-tolerant plants, we’re referring to both drought-tolerant and drought-resistant plants.
Features of drought-tolerant plants
Drought-tolerant plants have adapted through the years to survive in harsh conditions and regions where other plants have died, which means the plants we see today are the ultimate drought champions. These hardy plants use three major strategies to thrive in dry conditions.
- Drought tolerance
- Drought avoidance
- Desiccation tolerance
1. Drought tolerance
“Drought tolerance” is an umbrella term to describe the adaptations that make certain plants especially drought-hardy. Most drought-tolerant plants boast multiple drought-tolerant traits, so they aren’t relying on a single adaptation to carry them through the dry season.
Root adaptations
- Deep roots: Drought-tolerant native plants and trees have long, vigorously-growing taproots to dig under the soil surface and “root out” water locked deep underground. This means they can access water reserves when a drought hits, so they won’t feel the immediate stresses that shallow-rooted plants experience.
- Lateral spreading roots: Shallow, spreading root systems extend around the base of the plant to stabilize it and seek out surface water. The roots of the long-lived ponderosa pine can extend up to 150 feet horizontally. Drought-tolerant plants with shallow lateral roots often also have a deep taproot, so the roots access both deep groundwater and shallow surface water.
- Bulb-like roots: Some cacti like Pterocactus tuberosus have large, tuber-like roots that store water, so when a drought hits, the plant has its own underground water reserves that can last for years.
Leaf adaptations
- Tiny hairs (trichomes): Hairy leaves like those found on lamb’s ear and lavender shade the stomata to reduce transpiration (the release of water vapor from the plant leaves into the air) and protect the leaf surface from direct contact with hot, dry air. These hairs also trap water particles to be absorbed by the leaves.
- Small, thin leaves: The smaller the leaf surface area, the less chance of water loss. Many tough flowering plants like yarrow, Russian sage, tickseed, and moss verbena have petite, lacy leaves to minimize transpiration.
- Thick, waxy leaves: Succulents like agave and shrubs like bayberry have leathery, fleshy leaves that store water and a waxy coating (cuticle) that prevents water loss and reflects heat.
- Few leaves: The fewer leaves a plant has, the less susceptible it is to excess transpiration.
- Sunken stomata: Stomata that lie beneath the leaf surface are less vulnerable to transpiration than stomata that are directly accessible to the hot sun and dry air. Pine needles and desert xerophytes (plants adapted to dry conditions) have sunken stomata.
- Prickles and spikes: To stop thirsty animals from taking a big bite, drought-tolerant plants like the prickly pear cactus have spiky thorns. These thorns prevent plant damage and resulting water loss.
2. Drought avoidance
Drought-tolerant plants use special tactics to avoid the bulk of severe drought both daily and seasonally.
Nighttime activity
When the hot sun shines, some plants close their stomata (leaf pores) and instead open them at night. Closing the stomata limits transpiration so the plant can hold onto most of its water. (Remember, transpiration is the release of water vapor from the stomata into the air.)
At night, the plant can safely open its stomata and gather carbon dioxide while temperatures are cool and the sun isn’t stealing water. The plant can then use the stored CO2 for photosynthesis during the day without opening its stomata.
This process is called Crassulacean acid metabolism (CAM) and is used by succulents like cacti, jade plants, and sedums, and tropical plants like orchids.
Early seasonal growth
Some plants avoid drought by “frontloading” their growing season to avoid the peak of summer heat. Leaf growth requires massive amounts of energy and nutrients. By beginning growth in early spring and dropping their leaves by summer, plants conserve energy when the weather is at its hottest and driest.
Horse chestnuts, also known as buckeyes, are a prime example of shrubs that flower early and drop their leaves before the summer drought. Likewise, chaparral currants will go dormant during summer stress and resume growth in autumn once the rain has returned.
Spreading seeds
Just because a plant dies at the end of the season doesn’t mean it’s failed the drought test! Drought-tolerant annuals like California poppy avoid drought by dropping thousands of hardy seeds before they die. These seeds sit on the soil surface waiting for the next rain to fall. When it does, they spring to action: New plants germinate quickly, grow strong, and produce more seeds to continue the cycle.
3. Desiccation tolerance
When a plant fully dries out (desiccates), it dies, but some plants withstand extreme drought and come back to life once water is available.
Resurrection plants like ferns and moss (especially Selaginella lepidophylla) can lose more than 90% of their water content without dying. They stop growing, turn brown, and dry out during periods of drought, but they’ll perk up and turn green before your eyes as soon as they receive water.
Resurrection plants can survive as long as three years with no water. Once watered, they recover and start growing again in a matter of seconds up to a few days.
How do resurrection plants work? Just like other plants, when the soil starts drying out, their roots send a message to their leaves to close their stomata. If the drought persists, resurrection plants carefully curl their leaves, stop photosynthesis, and turn brown or purple (plants with purple leaves are producing anthocyanin, which acts as a sunscreen).
The ability to desiccate and fold their leaves without damage or death makes resurrection plants unique. How do they do it? Resurrection plants …
- Accumulate protective sugar and protein molecules to prevent damage to cell structures and promote recovery once water is available.
- Have flexible cell walls that are less susceptible to cracking. Unlike the cell walls of normal plants, drought-tolerant cell walls can fold and shrink during dry spells without breaking.
- Prevent the buildup of harmful free radicals by accumulating beneficial molecules. (Free radicals are highly reactive molecules produced during photosynthesis that can damage cells)
Benefits of drought-tolerant plants
Whether you live in a region prone to droughts or just want to make your yard more water-wise, drought-tolerant plants are an excellent alternative to thirsty turfgrass and high-water species.
Drought-tolerant plants …
✓ Save time on lawn maintenance like mowing
✓ Save money on chemical treatments like fertilizing and applying herbicide
✓ Lower your water bill
✓ Protect the environment from polluted runoff
✓ Prevent water shortages
✓ Promote biodiversity and attract endangered species
✓ Reduce lawn erosion during heavy rain
✓ May provide access to financial incentives like xeriscaping rebates
How to prepare your yard for drought-tolerant plants
If you’re sick of your so-called perennials withering and dying the moment they step root in your yard, it’s time to consider drought-tolerant plants. Here’s how to prepare your yard for healthy, low-maintenance plants.
1. Test your soil. Order a soil test from your local cooperative extension to determine your soil’s pH and nutrient profile. This test will inform what soil amendments you need and what type of plants will thrive in your yard.
2. Amend your soil, if needed. For example, if your soil is heavily acidic, you may want to add lime to raise the pH. If your soil is more alkaline, you may want to add sulfur to lower the pH. Beware before reaching for the compost or rich manure, though: Many drought-tolerant plants actually prefer poor, dry soil.
3. Choose the right plants for your lawn. If your soil is sandy, you may consider a mulga tree. For more clay-heavy soil, you might opt for an eastern red cedar. Take sun exposure into account: Yarrow requires full sun, so if your lawn is partially shaded, you may want to plant purple coneflower or blanket flower instead.
4. Hydrozone. Plan out your landscape so plants are grouped together based on their watering needs. That way, you aren’t overwatering drought-tolerant plants or underwatering plants with higher water requirements.
5. Care for your new plants. Water your plants daily for the first week, and then water them weekly or twice a week (1 inch of water total) for the first two years to give them time to establish. After the two-year mark, you can toss the hose and enjoy a beautiful, self-sustaining landscape.
Best drought-tolerant plants for your yard
There’s a treasure trove of drought-tolerant and drought-resistant plants at your fingertips, many of which are eco-friendly native species that attract pollinators. Check out these popular dry weather winners.
- Bur oak (Quercus macrocarpa)
- California buckeye (Aesculus californica)
- Common hackberry (Celtis occidentalis)
- Eastern red cedar (Juniperus virginiana)
- Eastern redbud (Cercis canadensis)
- Golden rain tree (Koelreuteria paniculata)
- Maidenhair tree (Ginkgo biloba)
- Mulga (Acacia aneura)
- Northern catalpa (Catalpa speciosa)
- Ponderosa pine (Pinus ponderosa)
Shrubs:
- Adam’s needle (Yucca filamentosa)
- California lilac (Ceanothus spp.)
- Century plant (Agave americana)
- Chokeberry (Aronia arbutifolia)
- Common lantana (Lantana camara)
- Evergreen sumac (Rhus virens)
- Elderberry (Sambucus nigra)
- Glossy abelia (Abelia x grandiflora)
- Panicle hydrangea (Hydrangea paniculata)
- Russian sage (Salvia yangii)
Perennials and ground covers:
- Blanket flower (Gaillardia grandiflora)
- Butterfly weed (Asclepias tuberosa)
- Carpet sedum (Sedum lineare)
- English lavender (Lavandula angustifolia)
- Foxglove beardtongue (Penstemon digitalis)
- Globe thistle (Echinops ritro)
- Lamb’s ear (Stachys byzantina)
- Purple coneflower (Echinacea purpurea)
- Tickseed (Coreopsis spp.)
- Yarrow (Achillea millefolium)
Ornamental grasses:
- Big bluestem (Andropogon gerardii)
- Blue oat grass (Helictotrichon sempervirens)
- Elijah blue fescue (Festuca glauca)
- Fountain grass (Pennisetum alopecuroides)
- Hairgrass (Muhlenbergia capillaris)
- Leatherleaf sedge (Carex buchananii)
- Pampas grass (Cortaderia selloana)
- Purple needlegrass (Stipa pulchra)
- Switchgrass, also known as panic grass (Panicum virgatum)
- Zebra grass (Miscanthus sinensis “Zebrinus”)
Want a list of drought-tolerant plants for your specific region? Check out your local university extension program or botanical garden website. Many extensions and gardens offer comprehensive drought-tolerant plant lists like Clemson University’s “Plants that Tolerate Drought” and the Greenbelt Native Plant Center’s “Drought-Tolerant Species.”
FAQ about drought-tolerant plants
A xeriscape is a low-water landscape design that thrives on your region’s natural rainfall, which means it requires little to no supplemental watering. When you xeriscape, you replace some or all of your thirsty turfgrass with drought-tolerant native plants, mulch, rocks and gravel, and hardscape features.
Check your local government’s webpage to see if xeriscaping your lawn or sidewalk strip may qualify you for a rebate, and then follow their xeriscaping guidelines. Most xeriscaping programs require a certain depth of mulch (usually 3 to 4 inches deep) and have a minimum size requirement.
Drought tolerant plants are excellent additions to xeriscapes, rock gardens, and cottage gardens, around stone footpaths and patios, and on the outside edge of rain gardens. They provide color and texture to your landscape without the water waste.
Transpiration is the evaporation of water from the leaves, stems, and flowers of the plant. It occurs when water vapor from the stomata is lost to the air.
Transpiration is a natural process in plants, and it happens a lot more than you think: More than 99.9% of the water a plant absorbs through its roots is transpired through the leaves, while only 0.1% of that water is actually used to grow new plant tissue. However, that 0.1% of water makes the difference between life and death for drought-tolerant plants. That’s why they have special strategies to limit excess transpiration.
When dry weather hits, plants quickly produce a helpful hormone called abscisic acid (ABA), which travels to the stomata to help them open and close. ABA controls turgor pressure (the pressure exerted against the cell wall): When turgor pressure is low, the stomata close, and when pressure is high, they open. ABA decides when the stomata should open to take in CO2 for photosynthesis and when they should close to prevent water loss.
Drought-tolerant plants aren’t immediate drought superstars. It takes about two years for most plants to establish, and some trees take closer to four or five years. While plants are getting established, you’ll need to water them consistently.
Enjoy dry weather with drought-tolerant plants
Dry summers are perfect for sunny days by the pool — not sweaty mornings spent watering your lawn. Drought-tolerant plants are specially adapted to stand strong and resist withering when dry weather hits. Whether you’re eager to flip your lawn to a xeriscape or just want to plant a few drought-tolerant plants to border your mailbox, these hardy growers will fulfill your low-water lawn needs.
Want to skip the sweaty digging and get right to the “low-maintenance” part of drought-tolerant plants? Call a local lawn care pro to install your new drought-friendly plants so they start the growing season strong.
Main Photo Credit: Peter Burka | Flickr | CC BY-SA 2.0