Ornamental groundcovers that work well when the well runs dry
Water is waning and landscapes are feeling the squeeze. Lawns and landscapes are increasingly left to languish under water use limits.
In response to this pressing problem, Levi Dreiling and Jacob C. Domenghini of Kansas State University’s Department of Horticulture & Natural Resources set out to separate the survivors from the strugglers. Their study spotlighted ornamental groundcovers and turfgrass species, probing performance under prolonged drought stress and pinpointing plants poised to persevere when precipitation and irrigation prove parsimonious.
Conducted in the Throckmorton Plant Sciences Center greenhouses in Manhattan, KS, the research unfolded twice in 2024, once in spring and again in summer. Six groundcovers – Dianthus caryophyllus (carnation), Lysimachia nummularia (moneywort or creeping jenny), Phlox subulate (moss phlox), Sedum album (white stonecrop), Stachys byzantina (lamb’s-ear) and Vinca major (greater periwinkle) – stood alongside three turfgrasses – Buchloe dactyloides (buffalo grass), Festuca arundinacea (tall fescue) and Poa pratensis (Kentucky bluegrass).
Established in nursery containers, the plants endured a deliberate dry down while researchers monitored air temperature, relative humidity and photosynthetically active radiation. As soil moisture slipped, scientists tracked visual quality, leaf water potential, volumetric water content and stomatal conductance, linking physiological signals with aesthetic decline.
For most species, beauty faded fast. In both seasonal studies, visual quality for many plants bottomed out by day 50. Leaves wilted, color dulled and canopy cover thinned as drought deepened. Yet a few formidable performers pushed back against the pressure.
Lamb’s-ear stretched survival to an average of 91 days across trials. White stonecrop stood supreme, sustaining acceptable quality for roughly 160 days. The warm-season buffalo grass also maintained respectable form far longer than most counterparts.
These resilient selections showcased steady stomatal control and slower soil moisture depletion, signaling savvy survival strategies.
When each plant reached its lowest visual rating, irrigation resumed. Recovery revealed even sharper contrasts. After 15 days, green cover was sparse across the board, but buffalo grass led the laggards with about 15% green cover. Carnation, phlox, lamb’s-ear and periwinkle showed zero resurgence – their drought damage decisive and irreversible.
After 60 days, buffalo grass bounced back boldly, surpassing 90% green cover and signaling strong regenerative capacity. Tall fescue and white stonecrop staged moderate comebacks at around 50% green cover. Again, carnation, phlox, lamb’s-ear and periwinkle never recovered, underscoring susceptibility when water wanes too long.
The second summer study mirrored these patterns, though overall recovery was reduced, likely due to intensified evaporative demand and a greater vapor pressure deficit that sped soil moisture decline.
Physiological findings fortified the visual assessments. As volumetric water content dropped, leaf water potential became increasingly negative and stomatal conductance constricted, reflecting plants’ attempts to conserve moisture. In the summer trial, these shifts occurred more swiftly, emphasizing how seasonal severity compounds stress.
The data painted a clear portrait: species that slowed water loss and tolerated low tissue hydration sustained quality longer and recovered more robustly.
For landscapes facing fierce drought potential and strict water restrictions, buffalo grass and white stonecrop emerge as sensible, strategic selections, particularly in non-recreational settings where resilience outweighs refinement. Tall fescue, moneywort, Kentucky bluegrass and periwinkle fit sites with intermittent irrigation, offering acceptable endurance with occasional relief.
Phlox, carnation and lamb’s-ear falter under prolonged dryness and limited irrigation, making them risky choices where rainfall is unreliable and restrictions routine.
In a future framed by frugality and fierce climate variability, plant choice becomes powerful policy. By pairing prudent selection with purposeful management, landscapes can remain resilient, resourceful and remarkably refined even when water works on a whisper.
by Enrico Villamaino
