Plant This, Not That: Native Plant Alternatives to Common Garden Plants Pat Hayward
By Pat Hayward:
As Jennifer Bousselot explained in last month’s “Plant This, Not That” column, when switching over to natives or starting a new native garden, shrubs are a good place to start because they're “scaffolding” plants. Ornamental grasses and perennials are likewise important elements of the garden framework, especially larger-growing species. To that end, consider the following waterwise, native ornamental grass and spreading perennial to common, non-native water-hungry garden plants.
Ornamental grasses that self-seed are the bane of gardeners and commercial landscape maintenance folks alike. As ancient life forms, grasses and grass-like species evolved to be wind-pollinated, requiring no specialized insects to set seed. The seeds themselves are generally light weight and able to disperse through wind, or by attaching to a creature or object that helps the seed spread mechanically. It’s because of its success at procreation and distribution (think cheat grass) that Karl Foerster feather reed grass, a sterile selection, has become pervasive in landscapes across the country, including Colorado. It’s one of very few ornamental grasses that is completely sterile.
Unfortunately, exotic ornamental grasses such as miscanthus and hardy plume grass are still used extensively in designs (particularly commercial) yet are becoming more prevalent on states’ noxious and invasive weed lists. They’re especially threatening to riparian areas, and once established, eradication becomes exceedingly difficult.
Miscanthus is more of a problem in moister eastern and southern states, but Eurasian hardy plume grass (Saccharum [Erianthus] ravannae) is now invasive in six western states, including Colorado (invasiveplantatlas.org, moabsunnews.com), even though it’s still recommended by state universities and listed for sale at most local retail and wholesale nurseries!
Giant Sacaton (Sporobolus wrightii)
Instead of hardy plume grass, consider using giant sacaton (Sporobolus wrightii), a large clumping grass native to the southwest (CA, UT, AZ, NM, TX, OK). It grows to 6' tall or more and to 5' wide and is hardy to at least USDA Zone 5. It breaks dormancy in late spring with bloom stalks appearing late summer. It rarely self-seeds because of the late bloom time, reducing the opportunity for seed to ripen. Flower spikes hold up into early winter, and the fountain of foliage offers a strong winter focal point. Stalks are tough and rigid, but try to cut the foliage back as close to the ground each spring as possible to maintain the neatest appearance. Giant sacaton requires no additional irrigation once established, but will tolerate occasional irrigation, especially in the hottest parts of summer.
Desert Four O’clocks (Mirabilis multiflora)
Not every garden has room for the sizeable perennial, Desert Four O’clocks, but it’s a summer evening star for those that do. Like its cousin Mirabilis jalapa, the annual four o’clocks, flowers of this southwestern native (CA to TX, including CO) open in late afternoon. This adaptation of bloom time coincides with the flight of the plants’ primary pollinators, the white-lined and five-spotted sphinx moths. The caterpillar phase of sphinx (or hummingbird) moths are hornworms, including tomato hornworm, so remember that when you see horn worm damage on your precious tomato plants! Hummingbirds and butterflies are also attracted to the flowers, while deer and rabbits shy away from browsing these plants.
Desert four o’clocks can grow to 18" (or more) tall by 4-6' wide and are hardy to USA Zone 4. They thrive in the hottest, driest conditions in full sun, and prefer soils that are lean and low in organic matter. Flowers are magenta-pink and shaped like small petunias. Once established, they require no additional irrigation.
Because of their considerable size, brilliant blooms, and resilience to tough conditions desert four o’clocks should certainly be used more in commercial plantings, including roadways, HOA and business entrances, and parking strips. Use them instead of high- and moderate water-requiring, sun-loving annuals such as petunias and calibrachoas. Collette Haskell at Nick’s Garden Center recommends planting desert four o’clocks instead of overused landscape roses, spireas, and dwarf buddleias. Amy Yarger of the Butterfly Pavilion suggests they could even be used as an alternative to the very prolific Jupiter’s Beard (Centranthus ruber). The biggest drawback to these plants is how gangly and awkward they look in containers. That scrawny-looking specimen will surely grow to a magnificent diva once planted in the ground.
Pat Hayward is a long-time Colorado professional horticulturist now specializing in gardening communications and education.