Don Kinzler, Published December 13 2013
Growing Together: Time to test your knowledge of holiday plants
Have you seen the new colors of poinsettias? Various shades of red, pink, white and speckled were developed by natural plant breeding. But how about the bright blue, purple and even orange specimens? And the flower bracts are glittery? I know Mother Nature doesn’t sprinkle her handiwork with gold glitter, so I decided to do some investigation.
The unusual colors are produced by spray-painting white poinsettias with vegetable-based dyes and then adding glitter while still wet. I peeked underneath the bracts, and sure enough, they’re white. I will admit they are pretty, so I won’t make disparaging comments questioning the morality of spray-painting plants and then dousing them with glitter.
Let’s test our holiday plant IQ with a true-and-false quiz:
Q: Poinsettias are poisonous.
A: False. They do exude a milky sap that can be a skin irritant, but America’s foremost poinsettia breeder, Paul Ecke, has eaten leaves numerous times on national television to prove their safety.
Q: Poinsettias are tropical in origin and should be kept warm.
A: True. When purchasing, insist that the retailer enclose the plant in a plastic bag secured at the top, enclosing it in a bubble of warm air. Even a few minutes exposed to temperatures below 45 degrees can cause irreversible damage. Protect poinsettias as you would an unclothed baby.
Q: Because they’re tropical, poinsettias should be placed close to a home’s heaters.
A: False. Although they don’t like being chilled, they also resent dry heat blasts indoors. Produced in greenhouses at temperatures between 60 and 70 degrees, they’ll appreciate similar conditions in the home, and added humidity is always a plus.
Q: Poinsettias should be watered every day.
A: False. The life of your plant will be decreased by both overwatering and underwatering. Water when the top inch of soil feels dry to the touch but you can still feel moisture below. If the pot is wrapped in foil, poke holes in the bottom for drainage. Apply enough water to wet the entire soil ball, but never allow the plant to stand in water.
Q: Poinsettias should be placed in sunlight.
A: True. They’ve been grown in sunny greenhouses, so providing sunshine in the home will keep them growing longer. It’s fine to display them in other locations if you aren’t intending to keep them past the holidays.
Q: Getting a poinsettia to re-bloom is difficult.
A: False. It’s easy, but it takes commitment.
Keep them growing in a sunny window for the rest winter. In early June, cut back to 4 inches above soil line, repot if needed, and sink pot and all into a sheltered flowerbed receiving full or half-day sun.
Bring back indoors in late August to a sunny window. On Oct. 1, begin a daily regimen of nine hours light and 15 hours dark, by covering the plant at 5 p.m. and uncovering at 8 a.m. until Dec. 1.
Flower bract formation is triggered by short day length, which occurs naturally in late fall, but our indoor lighting stymies the process, and so the need for covering the plant.
Q: Because Norfolk Island pine is an evergreen, it doesn’t need to be covered when purchasing in cold weather.
A: False. They’re evergreen but tropical. Cover all plants when purchasing and transporting during winter, especially across the parking lot to your vehicle. Enclose in a plastic bag warm air bubble.
Q: Norfolk Island pine can be grown as a houseplant.
A: True. Give it bright light with some direct sunlight in winter. Water thoroughly when soil feels dry. Dry heat and low humidity cause browning of needles, coupled with susceptibility to tiny spider mite invasions.
Q: Grandma was able to grow a Christmas cactus better than we can.
A: Probably true. Unless you’re turning your thermostat back at night. Flower buds are triggered by night temperatures between 45 and 55 degrees, which were common in older homes.
In today’s homes, proximity to a window can give a cooler microclimate, or locate the plant in a less-heated room. If night temperatures are kept closer to 70 degrees, a Christmas cactus can only be coaxed into blossoming if given a daily dose of 13 hours of uninterrupted darkness beginning in October.
Q: Because they’re a cactus, a Christmas cactus should be allowed to dry out thoroughly between waterings.
A: False when in bloom, true otherwise.
Although over-watering is a sure recipe for rot, when in bloom they require a more consistent moisture supply. Wide swings in moisture coupled with dry air cause unopened buds and blossoms to drop prematurely.
For after-holiday care of less common plants, feel free to email me.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler’s Greenhouse in Fargo. Readers can reach him at firstname.lastname@example.org.