Drifts of groundcover are naturally beautiful and unifying elements in gardens. Yet these innocent-looking plants can become an H20-ingesting Little Shop of Horrors. It’s the nature of an abundance of alluring smallish plants, each dependent on a little irrigation.
Three sustainability pitfalls stem from groundcover’s seductiveness. Initially, with human nature being what it is, plants are set close together so emitter tallies escalate. That misstep led to our Myoporum parvifolium, Senecio mandralisceae, and Sedum rupestre consuming almost as much as the lawn they replaced. The remedy was to axe 80% of the new plants and cut flow rates on the rest.
Next, while lawn substitute examples such as Carex save water with less frequent irrigation, their plant proximity warrants spray. But spray uses 2 to 5 times more water than drip due to shooting beyond roots, wind, runoff, and evaporation according to WaterSense, Alliance for Water Efficiency, and others. Once rationing zeroed in on that reality, we removed our sprays and sprayees.
Finally, most groundcover easily propagates. ‘Free’ plants spring from nature’s miracles, but water use make free a mirage. A prime example is blue senecio, called “velvet on which to set your garden’s jewelry” by Dave Bernstein in Debra Lee Baldwin’s Los Angeles Times article. When cuttings expanded to use 8% of our water, we retrenched by reducing flows on those in 2 beds and replacing those in 3 beds with a few wider Portulacaria afra ‘Prostrate Form,’ Bougainvillea ‘Rosenka,’ Salvia leucantha ‘Midnight,’ and mulch.
So what’s a water-constrained gardener to do? Recognize groundcover is universally regarded as any plant that grows over ground to “provide protection from erosion and drought, and improve appearance by concealing bare earth.” It is rarely, if ever, the garden’s star. So use it sparingly as a supporting player and embrace the glories of broad plants and versatile mulch.
The pithy guide below shows how to rethink groundcover for water wise gardens:
|Old Que Sera Sera School||New Sustainability School|
|USE||Filler of big areas or backdrop to stars||Only ones you love, in moderation|
|SELECT||Based on color, flower, or other attribute||Only those that spread wide and far|
|SPACING||Close together to fill in quickly||At mature width to fill in over time|
|IRRIGATE||Spray emitters||Low flow rate drip emitters|
|MULCH||Covered by plant material||Visible design element|