by Helen Gordon, Kitchener Master Gardener
The Poinsettia (Euphorbia
pulcherrima) is a shrub in the Euphorbia family native to Mexico and Central
America. So we know that it wants a warm home. In fact it grows best at temperatures
of 20C daytime and 16-17C nighttime. Exposure to cold, even for
a brief period, causes it to droop and lose its leaves. So choose and transport
your Christmas plant keeping it cosy.
The brightly coloured parts of the
poinsettia are not the plant’s flower. They are actually modified leaves (bracts).
The flowers are the yellow-green knobs
at their centre.
Poinsettias exhibit photoperiodism flowering
in response to day length. To begin flowering
they need 12 to 14 hours of uninterrupted darkness for 7 to 10 weeks. They
bloom when nights are long and days are short.
The true flowers fade quickly but the coloured bracts last for four
months. This makes them ideal for indoor colour in winter.
- Place
your plant where it will get as much indirect sunlight as possible. Choose a
place without drafts, hot or cold.
- Water
it sparingly allowing the soil surface to dry out slightly between watering.
- There
is no need to add fertilizer until April when 20-20-20 will help new growth
along.
It
is fun to try to keep your plant from year to year. I had one re-bloom for five
years until it got nipped by a late Spring frost in the garden. The secret is
to prune it and repot it in late April. Cut it back by a third and mist it
well. (The cuttings can be rooted as well.) Fertilize it once new growth
appears. Set it out in semi-shade when all risk of frost is past and the
temperatures in the 20C to 24C range.
Water it as needed to prevent the
plant wilting. Add a soluble fertilizer (20-20-20) every two weeks. Shape it
with a second gentle pruning in July or early August. Never prune after
September 1st. Bring the pot
indoors in early September.
From mid-September to mid-November
allow it bright light for ten hours followed by 14 hours of total darkness
daily for eight to ten weeks. This can
be done by covering the plant with a black garbage bag each night and removing
it each day. Or you can place the plant under a box or in a cupboard at night
and put it under a light each morning. Remember that even the light from a
streetlight can ruin the dark cycle.