Have you noticed the big white flowers blooming now along Route 1? Those are our hardy hibiscus, the Swamp Mallow, or Hibiscus moscheutos. It is one of our larger perennials, meaning the top dies back in winter but the roots live, unlike a shrub or a tree whose top does not die back, even if it loses its leaves. It brings a touch of the tropics to our gardens with its huge, exotic flowers, each lasting just a day.
This hibiscus grows anywhere from 3 to 6 feet tall, and almost as wide, with a number of sturdy, unbranched stems rising from a central crown in a vase shape. The leaves are a medium green, with a grayish cast which helps it reflect heat and thrive in our hot, humid summers. From mid-summer till fall, many large — 2 to 6 inches — flowers cover the plant. The flowers are generally white, funnel-shaped like a hibiscus with five petals, with a deep pink throat. Some can be a light pink, however.
The plant loves moisture. It will grow well in a low spot in your yard and can survive flooding, even some salt water (not a lot though — for that you’ll need its cousin, the Salt Marsh Mallow, Kosteletzkya virginica, also beautiful). It does well in our sandy soil but likes some organic matter — its natural habitat is fresh and brackish tidal marshes, or non-tidal freshwater wetlands — so you know it appreciates some muck to grow in. Mulch it well to preserve moisture and give it the organic matter it likes as the mulch breaks down.
It will survive some drought once it’s established, which, like any perennial, will take about a year, so water it deeply twice a week until then. It does need full sun (six-plus hours a day). It doesn’t need any pruning, just cut the dead stems back sometime in winter (many people like the look so leave them if you want till spring). It does come up late in the spring though, so leave a few inches of the stems to mark where it is, and don’t give up.
There are a lot of cultivars (cultivated varieties) available at garden centers which are breathtakingly beautiful. Starry Starry Night is a personal favorite with large pink and white blooms and deep maroon leaves only getting to about 4 feet. Ballet Slippers is also nice, and Luna Red is a deep red, shorter at 3 feet. But there are many more ranging in ultimate size. Try one or two in your garden today, you won’t regret it!