Drought-Tolerant Plants: Surviving and Thriving in the Heat

Some gardening seasons are better than others. Don’t look and learn only during the best years, but also when disasters such as drought strike. There’s a lot to be learned, such as the fact that butterfly bushes, sedum and grasses not only survive drought and heat that wipe out astilbe and daylilies, but also look good under those conditions.

Plants that Adapt and Overcome

This past summer, one of the hottest and driest in recent memory, unveiled a surprising discovery. While many species withered in the relentless heat and drought, a number of plants seemed to thrive, reveling in the challenging conditions.

As an avid gardener, I took note of these extraordinary survivors in my own garden and others. I compiled a list of plants that rely almost entirely on rain, perfect for designing dry, gravelly beds or areas where traditional watering methods won’t reach.

Hawthorns provide pleasant bloom in June, fruit for the birds, and respectable fall color. What a delight to know they also perform well in hot, dry places.

Not Just Drought-Tolerant, but Beautiful Too

Let’s not settle for mere drought tolerance, as it often comes at the expense of aesthetics. Take Joe Pye weed, for example. While it survives drought by hanging on until late June, its wilted leaves aren’t exactly a sight to behold. In my quest for resilient plants, I focused on those that not only fared well in drought but remained attractive as well.

So, what sets these winners apart from plants that wither and wilt in a scorching summer? After careful observation, I’ve identified several common characteristics that seem to give these plants an edge. Let’s explore these attributes, which can help you identify other hardy plants that can withstand hot and dry conditions.

Plants with Skinny Foliage

Plants with fewer and smaller leaves lose less water through transpiration on scorching days. This year, it became evident that some plants couldn’t handle the intense heat, even if they were drought-tolerant. They simply couldn’t absorb water quickly enough to replace what the leaves transpired.

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However, not all plants with tiny leaves are ideal for dry conditions. Cosmos and annual bachelor buttons, for example, are drought-tolerant but susceptible to mildew in stressful situations. Our high humidity provides the perfect environment for mildew to thrive, causing these plants to brown and curl.

Leaves Held Vertically

Leaves that stand upright escape the full impact of the midday sun. Bearded iris is a perfect example. It thrives when planted in that hot, dry strip between a driveway or sidewalk and a brick house foundation. Yuccas and many ornamental grasses also employ this clever tactic.

Even large leaves can survive in a drought if arranged vertically. Prairie dock and compass plant have huge leaves that stand straight up, resembling canoe paddles on a sandy beach. These plants impress me the most during dry years, standing tall and producing sturdy flowering stems.

On the other hand, understory species planted in direct sunlight, such as flowering dogwoods, Japanese maples, redbuds, and hydrangeas, wilt because their leaves are parallel to the ground. This position allows them to capture every ray of sunlight that filters through the forest canopy, but it also leads to wilting and a compromised ability to photosynthesize.

Leaves with a Furry Coat

The gray or silver hair on leaves acts as insulation. It traps water released from breathing holes, preventing direct evaporation. Even a small amount of hair, like the downy foliage of Tellima or the bristles on prairie dock and annual sunflower, can make a significant difference. Blue mist spirea and Russian sage have a coating on both their leaves and twigs, providing extra protection.

However, leaves may fail to develop their furry coating if grown in cool, moist shade. Blue globe thistle and dusty miller can lose their downiness and sag in the face of drought.

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Waxy Coatings on Leaves

A wax coating on leaves slows down water loss. Myrtle euphorbia’s wax coating allows it to withstand winter’s freeze-drying and still look cool and comfortable in the summer. Sea crambe, a waxy blue cousin of giant crambes, thrives even in the driest conditions.

Tap Roots

Plants with tap roots can draw water from deep underground, allowing them to survive for extended periods while other plants wither away. Some plants, like waxy myrtle euphorbia and yucca-leaf sea holly, possess both vertically-arranged leaves and tap roots.

Wide-Reaching Roots

Junipers, butterfly bushes, and hawthorns rely on far-reaching roots to survive drought. Their extensive root systems enable them to draw water from beyond their immediate surroundings.

Succulent Foliage

Cacti are well-known for their ability to store and utilize water during dry periods. Similarly, Michigan native prickly pear cactus and many sedums can make use of water absorbed weeks before.

Bulbous Plants and Others with Avoidance Syndrome

Certain plants, like tulips, daffodils, and foxtail lilies, have developed the “grow fast, then hide” strategy to cope with bone-dry summers. These plants rely on cool and moist conditions throughout summer to prevent ripening. Without proper ripening, they may fail to flower or develop a protective layer, leading to potential winter rot.

Nature’s Enigmas

Some plants seem to thrive in drought conditions without an obvious explanation. Hostas like ‘Gold Standard’ and ‘Sugar and Cream’ continue to stand tall, while other hostas succumb to the heat. Tovara, Solomon’s seal, and goatsbeard also perplex me with their ability to endure. These shade-loving plants could not solely rely on shade alone, as they thrived among other shade-loving species that couldn’t withstand the drought.

If you decide to grow any of the perennials or hardy woody plants from this list, remember that they may require some adjustment. If they were grown in a nursery or irrigated bed, they’ll need time to adapt their root system from a compact, watered-every-day ball to something larger and more extensive. Some may come to you with less hair or thinner leaves due to their protected growth environment. Once established, these plants will develop leaves suited for hotter and drier conditions. However, during the first year, provide water during dry spells to help your drought-tolerant plants shine in the face of future droughts.

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Butterfly bush may hang its leaves on the hottest dry days, but it comes through with flower even so. Now, if we could only help it stay ahead of the spider mites that also like hot, dry conditions!

Drought-Tolerant Plant Recommendations

If you’re looking to create a garden that can withstand drought and still provide beauty and color, consider these plant recommendations:

Annuals

  • Dusty miller
  • Gazania
  • Licorice plant
  • Red fountain grass
  • Sunflowers
  • Verbena bonariensis

Perennials

  • Allium
  • Amsonia
  • Baby’s breath
  • Barrenwort
  • Bearded iris
  • Blue globe thistle
  • Blue lyme grass
  • Butterfly bush
  • Catmint
  • Compass plant
  • Daffodil
  • Dianthus ‘Bath’s Pink’
  • Fountain grass
  • Foxtail lily
  • Goatsbeard
  • Goldenrod
  • Hosta ‘Gold Standard’
  • Hosta ‘Sugar and Cream’
  • Lavender mist meadow rue
  • Leatherwood fern
  • Michigan lily
  • Myrtle euphorbia
  • Perennial ageratum
  • Prairie dock
  • Prickly pear cactus
  • Rose mallow
  • Sea crambe, sea kale
  • Showy stonecrop
  • Solomon’s seal
  • Starry false Solomon’s seal
  • Tellima
  • Tovara
  • Tulip
  • Yucca
  • Yucca-leaf sea holly

Shrubs

  • Barberry
  • Blue mist spirea
  • Juniper
  • Siebold viburnum

Trees

  • Hawthorn
  • Honeylocust

Please note that some plants marked with an asterisk (*) should be grown in shade or partial shade.

Remember, selecting drought-tolerant plants is only the first step. During their initial growth, these plants may need some extra attention and watering to establish themselves. Once they’ve settled in, they’ll reward you with their resilience and beauty.

Article by Janet Macunovich and photos by Steven Nikkila, Ames Farm Center.