Rose-of-Sharon is one of those plants that seems to thrive on neglect. A shrub that produces its hollyhock-like flowers in August and September, I’ve seen it turn up its toes and keel over the in the rich soil of manicured gardens; yet in dusty, neglected little front yards on high-traffic streets downtown where little else grows, it blooms its heart out.

Hibiscus syriacus, as rose-of-sharon is know botanically, is a distant relative of the tropical hibiscus (H. rosa-sinensis) we grow as an indoor flowering plant, and also a cousin to the moisture-loving perennial swamp hibiscus with the dinner-plate-sized pink, red and white August blooms (H. moscheutos).

Although purported to be hardy to Zone 6 (U.S. Zone 5), I’ve found that although the double varieties will tolerate our cold winters, the luscious single cultivars are reliably hardy only in Zone 7 (U.S. Zone 6). More’s the pity because the doubles have the unfortunate habit of hanging onto their brown, withered blossoms rather than dropping them, even as new flowers open over an extended bloom period. And, since I’m listing faults, the doubles also remind me a little of those too-perfect tissue-paper blossoms on a wedding limo or a parade float. Still, apart from hydrangeas, there’s little in the way of shrubs that flower in late summer, so rose-of-sharon can be a most colourful addition to the back of the August border.

Garden companions include summer phlox, purple coneflower, blue globe thistle, fragrant Oriental lilies, and August-blooming monkshoods (Aconitum napellus).

Many nurseries also sell standard or tree-form rose-of-sharon. In the oddity department, you can even find one called 3-N-1 with blue, red and white cultivars grafted onto one shrub.

Rose-of-sharon prefers full sun or very light shade and is best in a spot protected from winter wind. It flowers best in reasonably good, moist soil; dry conditions can be fatal. Since rose-of-sharon blooms on shoots produced during the current season, it’s possible to keep it in check by pruning back the previous year’s growth to 3 or 4 buds in spring. However, like all plants, it’s better to let it attain its natural shape (which is rather rigidly upright) and mature height of 8-10 feet (2.6-3.2 meters).

Many gardeners are alarmed to find that their rose-of-sharon, perfectly healthy the previous summer, looks dead-as-a doornail in late May when lilacs, roses and other self-respecting shrubs are in bud or bloom. That’s the thing with this plant: it doesn’t leaf out until it knows for sure that winter is over, and if that means waiting until mid-June, wait it does. Just as you’re ready to yank it out and toss it on the compost heap, the stick-like branches slowly unfurl the three-lobed leaves that signal all is well and winter wasn’t really as nasty as you thought it was.

Adapted from a column that appeared originally in the Toronto Sun

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