Garden Detective: Make your own hardy hibiscus

I have a Minerva Rose of Sharon that I would like to clone. I have read the “how-to” directions, but none give the ideal time of the year to do so. Can you help me?

Bob Shapro, Fair Oaks

Despite its nickname, Rose of Sharon is not a rose but a hardy hibiscus – Hibiscus syriacus. “Minerva” is a hybrid, released in 1986, with large pink flowers. A favorite of hummingbirds, this plant can reach 10 feet high and 6 feet wide and thrives in full sun to partial shade.

This summer-flowering woody shrub may die back in winter, but unlike its tropical cousin – the familiar Hawaiian hibiscus – Rose of Sharon can bounce back from winter cold and is well suited to Sacramento’s USDA Zone 9b climate.

With that in mind, there are two periods to propagate this kind of hardy hibiscus. Before frost in fall, you can take healthy (green) cuttings of stem, about 6 inches long, and root the cuttings indoors during winter. Or you may make cuttings in late spring or early summer when they grow easily outdoors.

Either time, the method is the same. When you take the cutting, make a 45-degree angle cut (that allows for more surface area to root) just below a leaf node, where the leaf meets the stem.

Remove most of the leaves except for those near the top of the cutting. Gently scrape off the outer bark of the bottom inch of the cutting. Dip the bottom into rooting hormone (available at nurseries).

Plant indoors in a pot filled with a good rooting medium. Some gardeners recommend a 50-50 mix of peat moss and vermiculite (both retain water and keep the cutting moist). Others recommend two parts Perlite to one part peat moss. Water well.

Encase the cutting and pot in a clear plastic bag for the first two weeks. That holds in moisture. Gradually open the bag to expose the cutting to air and allow the new plant to start growing.

It takes six to eight weeks to take root. During this process, make sure the cutting receives sufficient light and stays moist. A sunny window, grow-light or fluorescent light is ideal. In summer, cuttings can be started in light shade outdoors.

Another method can be done in summer with little effort. Bend a cane of the shrub down to the ground. Weigh it down with a rock or brick, or tie it to a stake. Cover part of the branch (but not the growing tip) with soil.

Over several weeks, the branch will root where it meets the ground. After it has rooted, the branch can be trimmed from the mother plant and a baby hibiscus bush is born.

Rose of Sharon also can be grown from seed. Some varieties reseed so prolifically, they can become invasive.