By Andrew Bunting, PHS VP of Horticulture 

Global climate changes are creating unpredictable weather patterns across the globe, including extreme heat and periods of extended drought -- even in the spring, when many parts of the country are normally getting ample rainfall. To combat this growing concern, we need to be aware and mindful of creating gardens that are resilient and “tough” in these dry conditions, and that require minimal watering or rainfall. 

1. Prairie Plants 

Over the last 25 years, many of the great Midwestern prairie plants have risen in popularity and are now becoming staples in many gardens. Many of the prairie plants can grow in full sun and, because they have significant root systems, they can tap into water sources many feet below the soil surface.  There are many species of Silphium including the compass plant, Silphium lacinatum; prairie dock, Silphium terebinthinaceum; and cup plant, Silphium perfoliatum that are all members of the aster plant family.  They have architectural foliage and stature, and towering stems that can reach over eight feet tall covered in medium-sized, sunflower-like flowers in the summer. As the flowers fade, it is common to see the American Goldfinch grasping the stems with their small talons and feeding from the developing seed heads.  

Another relative to the Silphiums are the coneflowers, Echinacea. Perhaps no other prairie plants have exhibited such fanfare as this genus. There has been amazing hybridizing and selection of the purple coneflower, Echinacea purpurea in particular.  Both the Chicago Botanic Garden and the Mt. Cuba Center in Delaware have conducted trials of the purple coneflowers which are noted for the raised dark brown central seed head and radiating purple petals. ‘Pica Bella’ is one with pink-purple flowers, while both ‘Fragrant Angel’ and ‘Snow Cone’ have white flowers. Echinacea pallida has long stems with very reflexed pale pink petals that create a very architectural effect in the garden. The Tennessee coneflower, Echinacea tennesseenis has more stout petals that create a pinwheel-like effect in the garden. All the coneflowers are also great seed sources for seed-eating birds like the American Gold Finch, the Purple Finch, and a whole host of native sparrows. 

2. Great Grasses 

Many of the best ornamental grasses are classified as native, with many being native specifically to the prairies of the United States. Due to their significant root systems (some have been documented to reach over ten feet deep), they can withstand long periods where there is a lack of moisture. Prairie dropseed, Sporobolus heterolepis has stiff upright foliage that creates a mounded tuft up to one foot tall. Wiry flowering seed heads rise above the foliage in the middle of summer, creating an airy effect. While the flowers themselves are discrete, the fragrance when they bloom has been described as “fresh,” and “cilantro-like.”  In the fall, the foliage turns golden yellow. In addition to being drought tolerant, the prairie dropseed is one of the few grasses that can tolerate poorly drained soils.  

Also hailing from the prairie are the switch grasses, Panicum virgatum. Several decades ago, one of the first introductions was a selection with upright steely-blue leaves, ‘Heavy Metal.’  Today, there are dozens of fantastic selections for the home garden. ‘Northwind’ is very upright with green to blue foliage. The airy seed heads sway in the wind above the foliage. This is a clumping grass, so it is most effectively used in masses in the garden. Like all the switchgrasses, they turn a tawny color in the winter and provide significant winter interest. ‘Shenandoah’ has airy pink flowers and flushes of red in the summer followed by great fall color. A large-statured grass is the big bluestem, Andropogon gerardii ‘Blackhawks,’ which has emerging purple foliage that intensifies with the season. 

3. Xeriscaping 

Xeriscaping is an approach to growing plants that need very little moisture or water. In the Midwest or East Coast, these types of gardens might be a gravel garden, and in the Mountain States, West Coast, and Southwest, this might be a garden style that replicates native Southwestern plantings or a Mediterranean-style garden that is often seen throughout parts of California.  

There is a myriad of plant types that can be used in these gardens depending on the USDA hardiness zone. For example, Cacti are one of the best choices for the dry garden or xeriscape. While Cacti are an iconic plant of the Southwest and are seen in amazing collections at gardens like the Huntington Botanical Garden or the Ruth Bancroft Garden, Cacti can grow in many climates throughout the United States. There are many species of Cacti, e.g., Opuntia and Cylindropuntia and more, that are native to high elevations of Colorado, Wyoming, Idaho, Utah, etc. They are perfectly hardy and can grow quite well in many of the Midwestern states and the East Coast.  

Additionally, the prickly pear, Opuntia humifusa is found natively in almost every state east of the Mississippi River. This spreading cactus has beautiful yellow flowers and can be grown in gravel, sand, and other well-drained soils. Another versatile group of the dry garden is the yuccas. The Adam’s needle, Yucca filamentosa has a base of sharp, upright, evergreen leaves. It is native and is found growing in natural habitats throughout the southeastern U.S., but is exceptionally winter hardy in many other states. It sends up dramatic spikes of flowers in mid-summer that are covered in pendant, bell-shaped, creamy white flowers. The flowering stalks can reach eight to ten feet tall. ‘Color Guard’ is a selection with striated yellow and green leaves that is very good for winter interest.

Also, for great effect and stature in the xeriscape, there are dozens of species and cultivars of Agave. Agave americana has striking steel-blue leaves with amazing flower stalks that reach over 25 feet tall and are covered in clumps of tubular yellow flowers that can attract a myriad of hummingbird species depending on where it is grown in the country. Hardy in Zone 8, Agave americana is best for the southern and western parts of the United States.

Feel free to contact the horitculture experts at PHS when you have questions in these areas!