Hibiscus Solved

By: John Degroot

June 9 2012

Hibiscus Solved - Garden Clippings for June 9, 2012

Can a plant be an annual and perennial and flowering shrub?  Only if it is a Hibiscus.

If we lived in the Caribbean or anywhere in the world where temperatures don’t reach the freezing point, the only Hibiscus we would know is one that grows to become a large shrub or small tree.  In tropical climates it is so common that it is almost weed-like.

That same Hibiscus grows as an annual here in Canada.  Its stunning flowers are highly decorative and will add thrill to a flower garden or container.  Enjoy your Hibiscus all summer long and bring it inside through winter where it will double up as a houseplant.

Hibiscus has dark green leaves that resemble small maple leaves.  Flowers are trumpet shaped and open wide to about 3 or 4 inches in diameter.  Flowers are bright and bold primarily in shades of red, orange and pink and also in white, pink and salmon.

Hibiscus flowers are not plentiful, but their large size and bright colours make them one of the showiest annuals.  The individual flowers won’t last long, perhaps only a day or two, but they produce new flowers as fast as old flowers drop.

Plant Hibiscus in well-drained soil with good fertility.  For best performance, find a spot in full sun.  Hibiscus loves heat, humidity and fertilizer so feeding with water soluble plant food will pay off handsomely.  Hibiscus makes a fine focal point or thriller for a container.  Use a good soilless potting mix and be faithful and generous with water.

In fall, when frost approaches, you can allow your Hibiscus to die off with the rest of your annuals, or you can bring it indoors to be grown as a tropical plant.  Give it plenty of light and with luck, it will continue to thrive.  You can expect the leaves of Hibiscus to suffer after bringing indoors, but in due time it will bounce back.  If you’d rather, cut the plant back and allow it to go dormant through winter, and then bring it outdoors again in spring.

The perennial form of Hibiscus is equally impressive but with flowers that are huge, sometimes reaching 12 inches in diameter.  This Hibiscus, sometimes called Rose Mallow, Swamp Hibiscus or just Mallow.  The plant has an informal shape, grows to 4 to 6 feet or more and is ideally suited for the back of a perennial garden.  Like the tropical Hibiscus, it wants a sunny spot with good garden soil, well drained with plenty of moisture.

Rose Mallow begins blooming in mid-summer and continues producing flowers into fall and right up to the first good frost.  In late fall, it dies down and goes to sleep and is ready to sprout again in spring.  It needs warm weather to grow, so it won’t begin to grow until after all other perennials are growing actively.

The final Hibiscus group is the outdoor shrub, most often called Rose of Sharon.  This shrub is a favorite for shrub borders because it blooms in late summer and into fall, when little else is blooming.  Flowers are similar to the tropical Hibiscus but longer lasting.  Use it in the rear of a shrub border where it can grow 8 to 10 feet high.  Give it sun and it will be happy.

Rose of Sharon can easily be pruned back to keep it smaller in height.  Do so in later fall or early winter in order to maximize flower production.  Like the perennial hibiscus, the Rose of Sharon shrub waits for warm weather to arrive before it decides to produce green leaves.