Poinsettias are part of a huge range of often hardy plants – perennials and shrubs – in the Euphorbia family. Euphorbias generally share the common name of Spurge, Milkweed or Mexican Flame Leaf. (Spurge, as it was once used in medicine as a ‘purge’ treatment. Milkweed for the white latex sap – which incidentally, is at least an skin irritant, or can lead to other problems if ingested.) It is widely grown as an outdoor plant in parts of Mexico – and other warm countries.
You don't have to discard that favorite Christmas houseplant - the Poinsettia - after Christmas. You can make it burst into colour next year as well. The year round treatment of Poinsettias discussed here! But first – your Euphorbia at Christmas.
At 55-60F red poinsettias will stay colorful for 6 weeks and white ones for about 2 months. The newer forms or cultivars often remain attractive until spring.
It is a mistake to think that the showy parts are the flowers. In fact they are called bracts – modified leaves. In the case of the Poinsettia, the bracts surround the central flower cluster m- they simply serve as attraction and landing point for pollinating insects. Few insects would see the flowers from afar! As with most bracts, they are a different shape to the rest of the foliage.
Highly regarded as a Christmas house plant, Euphorbia pulcherrima is often grown as a garden plant – year round in warmer countries. In the UK and other cold-winter countries, it is normally bought just before Christmas when the bracts are fully in flower. The bract colour timing for Christmas is a result of special daylight length regime by specialist growers.
The main requirement for success with your Poinsettia is a warm room – not less than 55 deg day or night. (Higher in the day – ideally ‘human comfort’ temperatures)
Firstly, avoid buying your Christmas Euphorbia from a street market our outside the florist shop. Even a short spell in such cold and draughty situations will set the plant back and maybe even result in total demise.
Watering should be kept to a minimum – allowing the soil to drain and dry before the next spell of water. Do NOT stand it in a saucer of water. This will invariably lead to root problems or rot. If you have ‘under-done the watering and the plant starts to wilt, a good soaking with lukewarm water will normally bring it back to condition. Again – do not stand it in water.
Weekly feeding with a dilute houseplant food will be beneficial throughout its colour time. Feed only when the compost is moist – even if that means water one day and feed the next.
Position the plant in a light well ventilated spot – preferably not directly on a window ledge – or in direct sunlight. Good light is essential, or the colourful bracts will start to turn green. Draughts are to be avoided, as is moving the plant from place to place. It likes to settle down in a comfortable place.
There are many different cultivars now with red, pink, yellow or cream leaves. The red will always be favorite (for me!)
The only insect pests of indoor-grown Euphorbia pulcherrima are whiteflies. They hide under the large leaves, but will soon fly around if the plant is disturbed. Aphids generally prefer a tastier sap snack.
Getting your Poinsettia in colour for next year!
Over-watering can lead to root rot.
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.
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 sap. Take care not to get any sap on skin - irritating at least. Powdered charcoal is also good to prevent the sap bleeding.
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.