Plant Profile: Hardy Hibiscus – Bringing the Tropics to Maine

Some of the most stunning plants in the late summer garden are the Hardy Hibiscus. Whether perennial or shrub, they bust forth with a plethora of tropical-looking blossoms in August and September, reminding us that summer isn’t quite over. Bees, hummingbirds, and butterflies all adore the trumpet-shaped blossoms and sweet nectar within, giving them a reason to stay around so we can admire their beauty a little bit longer.

There are several species of hibiscus that are native to the US, mostly the central and southern states, but some will survive and thrive up here in Maine! The most hardy, Hibiscus moscheutos, also known as Swamp Mallow or Rose Mallow, is native to wetland areas and along rivers from Texas to the Atlantic, and northward to Southern Ontario. The species blooms pink, but hybridizes quite readily, and varieties can be found ranging in color from palest pure white to deepest, darkest red, with color variations of swirls and eyespots. The blossoms themselves can reach ten inches in diameter, most lasting only a day, but the abundance of flower buds on a single mature specimen will continue the show for nearly a month. A single plant can reach 10 feet tall and wide, making it a beautiful centerpiece. Leaf color can range from solid green, to green with red tint, to a coppery color, found on a white-flowered variety called ‘Kopper King’. ‘Lord Baltimore’ is one of the best true red rose mallows, reaching a height of nearly 6 feet, and blooming continuously from late August through September. A companion, ‘Lady Baltimore’, has a slightly smaller flower at only 6 inches across, and blooms pink with a red center. ‘Blue River II’ is a pure white variety that is beautiful in a moon garden. The ‘Luna’ series is a shorter selection, reaching a mature height of only 3-4 feet, and is much better for small spaces.

Full sun and moist but well-drained soil is best for Rose Mallow. Rose Mallow is a woody perennial, so it can and should be cut right back to the ground in late fall after the leaves have fallen. Don’t worry, it will come back next year, and be just as beautiful! They can be late starters, so don’t worry if it doesn’t appear to be growing when the rest of the plants in the garden have nice green foliage on them. Few pests bother them, and though they can be a late season snack for Japanese beetles, the damage is hardly noticeable.

Hibiscus syriacus, commonly called Rose of Sharon, or Althea, is another excellent shrub for beautiful summer color. They are native to Asia, and are hardy to around zone 5, so will live quite happily in the southern portions of our state. They can reach heights of up to 15 feet, but can be kept smaller. It blossoms on new wood, so pruning can be done in the spring without fear. Full sun and well-drained soil are again good conditions when planting, and they benefit from a bit of shelter from the wind to help eliminate tip dieback in winter. They are very easy to propagate, either from stem cuttings or seed, and have some invasive tendencies. Cold winters will usually keep the seedlings in check, but we are watching the spread closely. Flower color ranges from pure white, through a full spectrum of reds, pinks, and purples, to a nearly true blue selection called ‘Blue Satin’. Red eyespots are common, as are double flowers. ‘Ardens’ is a double flowered variety that is a lavender-blue, and ‘Lucy’ is a double red selection.

The days will start getting cooler soon, but we can still enjoy what is left of summer, and imagine tropical breezes wafting through the hibiscus…