Question:

I have winter-hardy hibiscus - one tree and several bushes. I collected seeds from the bushes. Will they grow, and when should I plant them? Should the bushes be cut down, and how far?

- Joan M. Elm

Answer:

Hibiscus seeds should be sown outdoors in spring and should germinate easily. Some self-sow and germinate with no effort on your part.

For the winter, store collected seeds in a labeled paper envelope that is placed in a zipper-style plastic bag; keep this in the refrigerator until sowing. I suggest that you plant the seeds in two or three plastic pots in a sterile commercial soilless mix; since squirrels and other fauna seem incapable of leaving pots alone, cover with some screening. When the seedlings have developed two or three sets of true leaves, thin them.

But which "winter-hardy" hibiscus is involved? Rose of Sharon (

Hibiscus syriacus

) is a woody shrub that can be pruned pretty much as it suits your whim. It blooms in late summer on new wood, so there's no peril of eliminating flowers by pruning before winter, during winter, or in early spring. Note that this plant is considered an invasive exotic (it is native to China and India) because the old-fashioned fertile varieties produce so many volunteer seedlings.

But if you're lucky you have one of the native rose mallows, which look like bushes but perform as perennials, dying back to the ground over winter. Swamp rose mallow (

H. moscheutos

) has large flowers - sometimes 6 inches in diameter - in white, pinks or almost red. Its leaves are relatively large, pointed ovals.

Scarlet rose mallow (

H. coccineus

) has red flowers, also large, but the foliage is the way to identify it - the leaves are deeply palmate (like splayed fingers), and many a non-gardener has mistaken them for marijuana.

For both of the rose mallow, you may cut the stems to the ground after frost. They will sprout new growth in late spring.

Q:

Should I prune my spent

Clivia miniata

flower stalks? When is the best time to prune dead or damaged leaves?

- Jacky

A:

I'd get rid of the spent flower stalks promptly - they are, well, ugly. Remove crummy leaves as soon as you think they look crummy. But if your flowers were successfully pollinated, it isn't a spent flower stalk - the seeds are visually appealing, and you might even venture to plant and grow them.

In this world of a scrillion clubs and associations, there exists the North American Clivia Society. It may be found at

, and the site will give you an indication of how clivia breeding (and one-upmanship) has evolved well beyond anything a plant catalog or garden center would suggest. Clivia devotees without Internet access may contact the society's secretary, Kathryn Andersen at 610-933-1855 or 2565 Charlestown Rd., Phoenixville, Pa. 19460-2870.

Send questions to Michael Martin Mills, The Inquirer, Box 41705, Philadelphia, Pa. 19101 or gardenqanda@earthlink.net. Please include locale. Read his recent work at http://go.philly.com/michaelmartinmills.