Question:

What do I do with a gloxinia that has grown too sprawling to fit on my windowsill? It bloomed all summer, but by fall had stopped. How do I make it bloom next summer? Can I make cuttings from it?

- Hope Punnett

Answer:

All should be aware that gloxinia (

Sinningia speciosa

) is a fussy plant. Ron Smith, a horticulturist with the North Dakota State University extension service, writes, "They make good 'housewarming gifts,' but don't expect to see them there a year after giving them." Hmmph.

Here's what makes them difficult: They are gesneriads akin to African violets, also quite finicky. But African violets are daintier, and there's plenty of lore about their needs, so people aren't surprised by finickiness. Gloxinias are more exuberant, so why, some might wonder, can't they be treated like other houseplants? They need moist but not wet soil, no moisture on the leaves (rambunctious watering is a no-no), high humidity (but do not mist the leaves), night temperatures around 65 degrees, days around 75 but never up to 80, and bright indirect light (no sunny windowsills). Overwatering is perhaps the biggest contributor to their demise.

Classic gloxinias should be allowed to rest over the winter. When the plant goes into post-bloom decline, reduce watering, remove dry leaves, and allow the tuber to dry out. It should be stored in its pot in a cool location (60 degrees) for eight to 10 weeks. In spring, repot in new medium that is high in organic matter, and resume watering.

But, Smith points out, newer strains have been hybridized to come into flower quickly for sale; they die back quickly, too, and the tubers are too insubstantial to be coaxed into another season of growth and flowering. Sort of like paperwhite narcissus. If you do not know which gloxinia you have, treat it as an older strain; if failure results, oh, well, it may have been a new, "improved" variety.

Propagation is quite doable, if you have mature, healthy, undamaged leaves. There are two methods (with both, use a 50-50 mix of perlite and peat moss):

Method One:

Select a flat leaf; use a clean, very sharp blade (one book suggests a scalpel!) to cut the leaf into 11/2-inch strips, cutting perpendicular to the central rib or vein of the leaf.

Half-fill a small tray (such as a well-washed takeout food container with a fair number of holes poked in the bottom) with moistened perlite-peat mix. Place the leaf sections, separated by a half-inch, on the surface and use short wire hoops placed over them to keep the main veins in contact with the medium. Enclose in a clear plastic bag to maintain humidity. Keep at 65 degrees out of direct sunlight.

In a month, there should be tiny tubers forming at the main veins. After the leaf segments have rotted away, pot the little tubers at twice their depth and bide your time.

Method Two:

Select a whole leaf and with that sharp, clean blade remove it from the plant with a heel - a small piece of the main stem. Plant upright in the moistened peat-perlite mix in a small pot, such that the base of the leaf just touches the medium. Enclose in a plastic bag using some internal support to keep the bag from touching the leaf.

Follow Method One for temperature, timing, etc.

Ron Smith's accumulated tips on many topics (houseplants, trees, weeds, etc.) can be found at

. Keep in mind that he is writing for the Dakota climate, of course.

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