One of the questions I receive most often concerns how to get a poinsettia (Euphorbia pulcherrima) to bloom again at home in time for Christmas. It’s possible, if you act now. But there’s one thing I want to stress: the easiest way to get beautiful poinsettias for Christmas is to buy new ones. Home-grown poinsettias will never be as compact, with foliage as green and inflorescences as large as the plants you buy. That said, it’s not difficult to produce poinsettias that are a little puny, a little crooked, but still in full bloom for Christmas.

Le secret de la floraison
It’s important to know that the poinsettia waits for a celestial signal to bloom: a drop in the duration of daily sunlight. Like the Christmas cactus, the kalanchoe and many other plants, the poinsettia is a short-day plant. It therefore needs days of less than 12 days to flower. If the days always remain at or above 12 hours, it will never flower.
Outdoors, it’s easy to have days of less than 12 hours: from the autumnal equinox, which occurs between September 21 and 24, days last less than 12 hours, and this will continue until the spring equinox next year. In the garden, the poinsettia will automatically receive the signal to bloom. But the poinsettia is frost-sensitive and can’t be left outside for long in autumn. In our climate, therefore, we have to find another solution.
In our homes, the poinsettia is well protected from frost, but doesn’t get the signal it needs. This is because we light our homes artificially, extending the day to 14, 16, even 18 hours or more. In this way, the poinsettia continues to grow, but never flowers. We need to find a way to protect it from our mania for extending the day beyond its normal duration.
The “Cardboard Box” and “Closet” Methods
Traditionally, the poinsettia is placed in a closed cardboard box or wardrobe every evening, to be exposed to the sun again the following morning. Of course, this “night” must always last more than 12 hours. So people often set themselves a timetable: put the plant in the dark at 6 p.m. in the evening and take it out at 7 a.m. the next day, for example. And you must never break this schedule: just a few minutes too long at the wrong time and the plant won’t flower.
In fact, in greenhouses where poinsettias are grown, it’s often necessary to lay out black sheets on the side of the road, because it only takes the headlights of a car shining on the plants at the wrong time to stop or delay flowering. If you undertake this program, there’s no question of having an irregular schedule yourself: for the next 2 months, you need to be there at the right time to put your poinsettia in the dark or take it out in full sun. If you have to miss your duty because of a short absence, err on the side of excess: it does less harm to the plant to receive 2 or 3 days of darkness than a single night at 12 o’clock with 7 minutes of light!

The Cellar Method
Another technique is even more radical: we suggest placing the poinsettia in a cellar, wardrobe, closed box, etc., until it flowers, i.e. for 2 months or more. This technique is risky for the plant: it’s hit or miss. Without any light, the poinsettia can no longer photosynthesize, so its energy is rapidly depleted. But at the same time, at least the plant receives the signal to flower. Often the plant dies before flowering, or flowers a little and then quickly dies, completely exhausted by its ordeal. Sometimes, however, the plant manages to survive this extreme treatment without too many after-effects.
The laidback gardener’s method
The easiest way to get a poinsettia to bloom is as follows. Find a room in the house that you don’t light at night (a guest room, for example), but which is well lit by unobstructed windows, and remove all the bulbs from the lamps that light it. Now place your poinsettia there. This way, even if you accidentally enter the room in the evening and try to open the light, forgetting that the poinsettia is there and that even a few seconds of light can cause it to miss flowering, nothing will happen and the poinsettia will therefore endure short days without further effort. Even if your poinsettia is no longer in a busy room, you still need to maintain it: water it when the soil is dry to the touch, give it a weekly quarter turn so that it grows evenly, etc.
When Leaves Turn Color…

Whatever method you use, when the poinsettia bracts start to take on their final color (red, pink, white, etc., depending on the cultivar), there’s no need to continue with the short-day treatment: once flowering has started, it will continue on its own, even under long days. As it takes a little over 2 months to bring a poinsettia into full bloom, this is the right time of year to start the short-day treatment if you want to have your plant in bloom for Christmas.
Good luck and… Merry Christmas in advance!
Larry Hodgson published thousands of articles and 65 books over the course of his career, in both French and English. His son, Mathieu, has made it his mission to make his father’s writings accessible to the public. This text was originally published in Le Soleil on October 2, 2005.
We just put them out in the garden and let them bloom after Christmas. They are prettier if they can bloom without manipulation. They need harsh pruning afterward though, so that they do not get too lanky.