Plant people generally take midwinter in stride. After all, if not now, when will you rest? But even as you mull ordering from the seed catalogues that have recently arrived, some garden challenges are waiting unobtrusively for you.
Consider what's happened to your Christmas poinsettia. You could have predicted the plant's decline from the start. On the one hand, the green leaves dropped (one at a time or en masse) for want of nitrogen. If you had applied Peters's 20-20-20 fertilizer whenever the soil started to dry, no leaves would have dropped. It's a good point to remember for the future.
Poinsettias kept at temperatures at or below 60 degrees have not prospered, despite appearances to the contrary. Roots rot in cool environment, but it takes several weeks for the appearance of symptoms, generally drooping of leaves even though the soil is moist. If this occurs, bang the plant from the pot, cut away the jelly-like roots, then return the plant to the same plastic pot with fresh 1-1-1 soil having a pH of 6.
Now we come to healthy poinsettias, which have kept their colorful bracts and dark green foliage. While you want to perpetuate the plant as it is, this isn't your best option. Old leaves are just that and nothing more. Your smart move is to prune so you start growing the plant immediately.
Using pruning shears, trim all stems back to within four to five inches of the soil. Discard everything. Don't use these stems and stalks for propagating the plant; that will come in due time. Use a lighted candle to singe the ends of pruned stalks to stop the flow of the white fluid. For safety's sake, spray surviving stems with Safer's insecticidal soap to take care of any bugs.
Next, wet the soil thoroughly by applying warm water from the top. Wait a minute, then spoon off and discard the top inch of old soil, replacing it immediately with wet 1-1-1 soil (equal amounts of milled sphagnum peat moss, perlite and vermiculite) with lime added to adjust the pH to 6. Afterward, apply a small amount of warm water to eliminate air pockets. Let drain fully before moving the plant into bright indirect light in a warm room.
The care program that follows is designed to help this "stock" plant yield leaf-and-stem cuttings that will be used later to grow new poinsettias. Keep the soil lightly moist, using Peters's 20-20-20 instead of water. In normal-temperature rooms, you should be wetting the soil every four or five days. Consider keeping plants in your warmest room because growth will be faster and continuous.
After growth is well underway, finger-prune the ends of terminal shoots to create a bushy plant over the spring. When pruning, remove about an inch of stem-tip growth to stimulate branching. Normal greenhouse practice is to leave seven to eight leaves on the plant when you begin finger-pinching. Wait until new branches have five or six fully developed leaves, then pinch again so you leave only three or four developed leaves on each branch.
As for a timetable, leaf-and-stem cuttings will be taken in late May to propagate the plant, again in mid-July, and final cuttings taken the third week of August, after which the stock plant will be trashed. By then, you could have propagated as many as 100 new poinsettias.
For those holding on to poinsettias dating back to Christmas 1989, look for a half-dozen of the uppermost leaves to color up in the next two weeks. Enjoy this flowering while you can, but plan on a severe pruning of the stems between February and May. From then on, treat it as a stock plant, junking it in late August after final cuttings are taken.
Late January is ample time to start tuberous begonias on the path to spring growth. With begonias, remove tubers from peat moss containers. Place all tubers in a small plastic bag, to which you add a tablespoon of dry fungicidal powder, either Maneb or sulfur. Roll tubers in the powder to coat the outer surface, placing each tuber in its own paper bag, which is rolled up and closed at the top. Find a dark closet in a warm room and place the bags on an upper shelf. Bags should be left intact for almost a month until the first buds appear, after which tubers will be potted.
Jack Eden is the host of "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM).