You don't have to discard that favourite Christmas houseplant - the Poinsettia - after Christmas. Year round treatment discussed here!
At 55-60F red poinsettias will stay colourful for 6 weeks and white ones for about 2 months. The newer forms or cultivars often remain attractive until spring.
You can enjoy the challenge of bringing poinsettias into bloom for a second season by getting a head start on next Christmas. About 2 weeks after receiving the plant, fertilize it with a complete fertilizer. The plant should be fertilized every 7-10 days until the plant loses its bracts (coloured leaves).
The Euphorbia - Euphorbia pulcherrima has to be the all-time favourite Christmas Plant for indoors
Be sure to keep the soil moist until the plant drops its leaves. Then let the soil dry out and don't water it until the stems begin to shrivel or crack. Keep the plant in a cool, sunny place such as a basement window ledge.
Late April or early May, bring the plant out of its 'resting' stage. Cut the stems back to 3-5" from the soil and re-pot the plant if necessary. After re-potting, water whenever the soil begins to dry out - not too much until the new growth starts. Don't waste the stems - use the tips as cuttings - see below. This is the time to actually start preparing your Euphorbia for its next Christmas display.
Once the new shoots are an inch long, apply a complete fertilizer. When the new growth is 4-6" long, prune the plant to form the desired compact shape.
In mid September, your poinsettia will need complete darkness every day from 5 pm to 8 am so put a cardboard box over the plant to provide the necessary "short day". Continue the "short days" until the plant's bracts show colour sometime in late November or early December. The night temperature should be 60-65F to ensure flowering of the plant.
In areas of mild or hot summers, Poinsettias can be grown outdoors until autumn/fall when time to bring indoors before the frosts. They are surprisingly hardy. I have found one growing in the open ground near the summit of Thailand's highest mountain - also in several other high altitude areas! Not always totally frost free areas. I suspect that once established, the Euphorbia can probably survive a degree or so of frost! It will need a few seasons of frost-free growth first though - I think.
However, as a pot plant, once the bracts have changed back to green, the plants will be quite happy if cared for outdoors after the last of the spring frosts.
Poinsettias can be propagated from stem cuttings in spring. Best with a little bottom heat, so a heated propagator is a boon. The softwood cuttings - tip growths - should be cut cleanly from the plant, and the bases immediately dipped into warm water to prevent any bleeding of the milky say. Take care not to get any sap on skin - irritating at least. Powdered charcoal is also good to prevent the bleeding.
Hormone powder or gel dip is beneficial - if only because most a have a fungicide.
Getting the plants to flower the following winter is sometimes a problem - Read the procedure above.
Whiteflies are the main pest problem - easily found. Not too easy to deal with though. Killing whitefly is dealt with here.
Many problems with Poinsettias are bought about by sheer neglect of the plant after it has fulfilled its function during the festive season! Don't simply leave it in a corner and expect it to do well.
Poisonous - or not? There are conflicting theories as to whether this particular Euphorbia is poisonous. Most of the family are. Better to assume so.
By David Hughes - firstname.lastname@example.org