You loved your poinsettia during the holidays, but (news flash!) the holidays are over. Now your plant is starting to look a little sad. One overarching question courses through your brain. What am I supposed to do with the dang thing now?
Should you plant it outside? Should you grow it as a houseplant? Or should you just chuck it and buy a new one next Christmas? The answer depends on where you live and how much trouble you're willing to go to.
Outdoors Native to Mexico, the poinsettia (Euphorbia pulcherrima) doesn't like cold. If you live in the Coastal and Tropical South (USDA Zones 9-11), you can plant it outside and it will grow into a large shrub or small tree covered with blooms each winter. If you live farther north than that, your poinsettia will freeze into mush.
Indoors What about growing it indoors as a houseplant? That's fine, as long as you accept that it will never be as showy in bloom as it was when it first came from a commercial greenhouse that provided the perfect amounts of light, humidity, water, fertilizer, and growth regulator. Assuming you're cool with that, as soon as the poinsettia drops its green leaves, do this:
1. Cut it back to 4 to 6 inches tall and move it to a slightly larger pot with good drainage. Add new potting soil to fill the extra space.
2. Keep the soil moist, but never soggy.
3. Provide bright light.
4. Feed weekly with liquid houseplant fertilizer diluted to half-strength.
5. Every 3 to 4 weeks from spring until early September, pinch back the growing shoots, leaving only 5 to 6 green leaves per stem. After that, just let the stems grow.
6. Bring the poinsettia into the house in October, before your first frost. In order to set flower buds, it will need 14 hours of complete darkness per day for about 6 weeks. How you provide this is where the "how much trouble you're willing to go to" comes in. Some people move their poinsettia into a closet when they get home from work and take it out to a sunny window when they leave for work the next morning. Just remember -- without 14 hours of complete darkness per day for 6 weeks, it won't bloom.
7. When you begin to see the bracts at the top showing color, the dark treatment is no longer necessary. Your poinsettia can come out of the closet at last. Don't be too disappointed if the blooms are sparse and dinky. You won't be alone.
Heave-Ho! But because Grumpy would be disappointed, I always toss my old poinsettia into the compost and buy a new plant every year. This makes the poinsettia growers very happy.