When you think “wildflower,” what vision comes to mind? For the vast majority of American gardeners, it’s certainly not a 12-inch, hot pink, pinwheel-like hibiscus blossom. Yet there are hibiscus species native to much of temperate North America, and they have given rise to varieties that thrive as perennials in gardens as cold as USDA Zone 4.
Hybrid hibiscus entered the garden scene in the 1950s with Robert Darby’s ‘Lord Baltimore’, derived from several native species, including Hibiscus coccineus and H. moscheutos. The ’60s and ’70s saw additional hybrids enter the market, and later a slew of exciting introductions appeared from the famed Fleming brothers of Nebraska, including the still-treasured bronze-leaved ‘Kopper King’. Recent years have seen a wave of novel cultivars that are renewing interest in this beguiling summer bloomer.
Tips for growing hardy hibiscus
Hardy hibiscus are easy to grow. They prefer full sun. Although they can get by in a part-shade position, their best flowering will occur with more sun. Pinching back the stems as they grow, but prior to the formation of flower buds, can also promote a heavier bloom, since it will spur additional branching. Pinching back creates a shorter, bushier plant, too, although many of the newer cultivars boast naturally compact growth.
To keep the plant looking neat, with the focus on the flowers, deadhead spent blooms. This also prevents any self-sowing. The thick, woody stems can be left standing over the winter and then cut down to the ground in early spring with loppers or a hand saw.
Garden varieties of hardy hibiscus descend from species that naturally occur in swampy areas, so these perennials are not drought tolerant. They grow best in soil that drains well but remains consistently moist, and they will need watering in extended dry spells. Japanese beetles can be a problem with these plants, but because desirable wildlife such as butterflies and hummingbirds also visit regularly, pesticides are not recommended. An environmentally friendly control is to simply knock the Japanese beetles into a bucket of soapy water, where they will drown.
Hardy hibiscus are just that: hardy. They will prosper in USDA Zones 4 through 9. Provide a thick layer of winter mulch in the colder regions, but pull mulch back from the stems during the growing season to promote air flow.
The most difficult part of growing hardy hibiscus is exercising patience in spring, when they are notably slow to rise. In Zones 4 and 5, it may be mid- or late June before shoots appear, especially in a cold spring. There it may be helpful to leave short stumps when cutting back the prior year’s growth, as a reminder during spring planting of where the roots lie.
Companions for hardy hibiscus
Given their tendency to “sleep late,” hardy hibiscus need neighbors that shine early. The upside is that these bulky perennials can carry the show from midsummer into fall.
Peonies can be a good match for hardy hibiscus, since their shrubby shape and large flowers will hide and distract from the gap the hibiscus has yet to fill in spring. Better yet, plant your peony behind the hibiscus, so that when the latter reaches full size later in the season it can hide mildewed peony leaves. Salvia and veronica are other good spring-flowering companions to place in front of hardy hibiscus, since they can be sheared after bloom to open up the view of the hibiscus.
Repeat-blooming hardy geraniums can make a good skirt for this plant, since their habit remains low and their summer flowers often provide a color echo to the larger ones of the hibiscus.
Other summer-into-fall bloomers to place with hardy hibiscus include substantial perennials like ornamental grasses, various coneflowers and ironweeds. The annual cleome, or spider flower, can make a compelling neighbor, too, with its upright stems, heft and large flowers.
Although it may seem like a good idea to plant spring-flowering bulbs amid the hibiscus roots, the latter’s preference for more water in the summer can be a problem for most bulbs. A workaround is to use tulips and treat them as annuals, pulling them after they flower, since many of us find most tulips less than reliable to bloom a second year anyway.
Image courtesy of Walters Gardens