Carol Stocker will be online live to answer your holiday decorating questions Thursday, Dec. 5 from 1-2 p.m....Many houseplants that bloom in December have become staples of holiday decorating, including azaleas, Christmas cactus, cyclamen, kalanchoe, paper whites, phalaenopsis orchids, amaryllis, and, of course, poinsettias.
Hot, dry, modern houses, however, are a trial for most houseplants, including Christmas plants, which are happier in drafty old homes with uninsulated windows. If you are going to discard the plants after blooming, don't worry about providing ideal conditions. However, if you want to keep them long term, consider setting them up in a cool, sunny area, such as a porch or sunroom, to be brought out for display when company arrives. Don't put plants near a radiator or on a TV set or they won't even last through Christmas. Most have received enough feeding from the professional growers to glide through the holidays without more fertilizing. Careful watering, though, will prolong flowering.
Azaleas: Many of the Indian azaleas (Rhododendron simsii) purchased as classy decorations each holiday season will wilt and drop their leaves in a week. The usual culprit is hot, dry air. The secret of enjoying many weeks of bloom is to make sure the soil is always wet. Not just moist. Wet. Don't despair if they wilt. Many are grown in peat that can become impermeable after it dries out. Just soak the entire pot in a sink. These plants also need a cool but bright location that is not in direct sunlight. The ideal temperature is 50 to 60 degrees. Obviously, this is cooler than most houses, but you can compensate by misting the foliage daily, removing at the same time any spent flowers.
Indian azaleas will bloom again next winter if you move them to a cool room after flowering, continue watering, and start fertilizing. Let them spend the summer outdoors in their pots and wait until October to bring them indoors to help set new buds. Then put them in a bright but cool room. When the flowers open, move them to their temporary display area. If you want holiday azaleas to enjoy now but plant outdoors later, look for the less common Japanese azaleas (Rhododendron obstusum), which look similar but are winter hardy.
Christmas cactus: Both the winter-blooming Christmas cactus and its popular cousin, the spring-blooming Easter cactus, have willing dispositions and flat arching stems that terminate in colorful flowers. They don't need as much water as azaleas. They make the best long-term houseplants on this list, so don't throw them out. Instead, to get them to rebloom next year, decrease moisture to almost nothing after they finish flowering so they can have a rest period. Then trim the ends of the stems to increase branching (and flowering), and move them outdoors in a shady spot from June until frost is predicted. They form buds in response to shortening daylight, so keeping them outdoors as long as possible helps set their flowering clock. Back indoors, keep them dryish and cool until they bloom again, then increase watering. If your plants have scalloped stems instead of stem margins with pointed projections, don't expect them to rebloom for Christmas. They are Easter cactus.
Cyclamens: Most homes are too warm to keep these as long-term houseplants. With care, though, you can keep the little flowers with their elegant swept-back petals in bloom for several months. They like to be in a cool, bright, north window where they won't get direct sunlight, and should be moist at all times. Like African violets and gloxinias, cyclamens will rot if their leaves and crowns become wet, so immersing the pots just up to the soil line in a sink or bowl of tepid water for 10 minutes is the best way to water.
Most people discard cyclamens after they bloom. To try to keep them, reduce watering and stop feeding them to induce dormancy until midsummer. Then repot them with fresh soil mixture, making sure the bulb-like corms are one-third above the soil line, and resume watering and fertilizing. Put these in a north window where temperatures remain between 50 and 60 degrees after their summer outdoors.
Kalanchoes: These long-flowering plants have large flower heads in red, white, orange, lilac, pink, or yellow that make me think of a Mexican fiesta. The palette is just too sunny for Christmas, but they tolerate warm temperatures better than most plants. After they bloom, discard them, or prune the tops and place the pots on a shady windowsill. Keep the compost nearly dry for a month and then put them in a sunny window and water normally. Growers are able to make them flower at any season, but you can't, so if they do rebloom, it will be in spring 16 months later.
Norfolk Island pine: Often sold as miniature potted Christmas trees, slow-growing araucarias will eventually reach 5 feet and are easy to keep. They need repotting only every three years as they like to be root-bound. Water sparingly in winter, but mist them occasionally.
Paperwhites: These fragrant narcissus bulbs are usually grown on top of a bowl of pebbles covered with water that just touches their basal plates on the bottoms. This is where the roots will sprout, winding quickly through the pebbles to anchor themselves. Some people find the smell of traditional white paperwhites too strong and prefer the more softly scented yellow varieties. Give them the sunniest spot you can so they don't grow too tall reaching for the light. They will probably flop anyway, unless you tie them up. Discard them after blooming.
Phalaenopsis orchids: These flat-faced moth orchids are the easiest orchids to grow and make tasteful gifts. All orchids need high humidity, which can be achieved by misting the leaves and placing the pots on top of large saucers filled with pebbles in water that evaporates and creates a moist, mini-climate without actually touching the roots. An east- or west-facing window is best if you have some lightweight curtains to shield them from direct sun, which will cause brown spots on leaves. They will greatly benefit from some supplemental grow lights in the winter, as they need at least 10 hours of light a day to rebloom. Fertilize them during the summer months. Well-grown phalaenopsis will bloom year-round. They have no resting period, so keep them moist at all times.
Poinsettias: These euphorbias aren't exactly made of plastic, but they are treated with chemicals to keep them compact, and engineered to bloom for up to six months, longer than most of us would like. What we think of as flowers are really colored leaves. When buying plants, look for the true flowers, which are tiny yellow buds in the center of the flower-head. They should not be showing pollen. Let poinsettias dry out between waterings but water them immediately if the leaves begin to wilt. Misting is also beneficial.
Poinsettias should be discarded after flowering, but if you like a challenge cut the stems back to 4-inch stumps after the leaves have fallen and water them very little. In May, move them to larger pots with some new compost and increase watering and start fertilizing. Thin the new growth to five stems. They can spend the summer outdoors until the end of September. Then comes the hard part. You must cover them each evening with black polythene bags so they get exactly 14 hours of complete darkness until their unveiling the next morning. This will add a glum note to your decor, and if you forget to cover them for even one evening, your plants won't color up. After eight weeks of this, treat them normally and they will bloom for Christmas. Without the greenhouse-applied growth retardants, they will be taller.