Ask a Master Gardener: Getting poinsettias to rebloom requires some effort
Yes, you can bring a poinsettia back to its holiday glory, but it does take a bit of effort.
Q: A friend gave me a poinsettia last year, and I’ve kept it alive since then. This year, she gave me a new one, and now I can see how shabby I’ve let the old one become! It’s leggy and only has a few red leaves. Can I make it beautiful again? Can I do better with the new one?
A: Yes, you can bring a poinsettia back to its holiday glory, but it does take a bit of effort.
I’d suggest treating both poinsettias the same way at this point, so they get onto the same cycle and give you a colorful show again next December.
In January, give them a bit of fertilizer and put them in a sunny window that isn’t subject to cold drafts, or put them under a shop light on a timer so that they get 6-8 hours of bright light every day. They prefer about the same temperature as most of us do: 65-70 degrees. Avoid putting them in a spot that is subject to cold drafts. Like other indoor plants, they should not be set directly on a radiator or in front of a heat vent.
It's a good idea to remove any fancy foil around the pot so that it can drain when you water it.
In February, trim back your leggy plant — and trim the new one if it has become leggy. Leave a good 6 inches. You can trim it back again in early summer to encourage it to bush out a bit.
Once summer is really here, you can put the plant outdoors. As with any plant you’re moving from indoors to outdoors, you’ll want to introduce it to outside conditions gradually. Keep it in the shade for a day or two, and bring it back in after a couple of hours. Gradually increase exposure to wind and sun. Eventually, let it spend the summer in a spot where it receives part to full sun.
The fussy part comes in the fall. By September, you’ll want to have brought the plant back inside, and in late September, you need to start giving it a prolonged period of absolute darkness every day. It needs eight hours of light and 16 hours of dark. You can put it in a closet if no light seeps in around the door. Seriously — no light at all. You can also just put a box over it.
This dark-light treatment goes on for two months. Then, you can put the plant back in a sunny window or under a light. If all goes well, you should be rewarded with new whorls of colorful leaves and two lovely plants — or maybe three, if your friend gives you another.
Unless she gave you a blue one. There are no natural blue poinsettias, and the ones that you can buy that are blue actually have cream-colored leaves that have been painted. They’ll come back cream-colored. But that’s pretty, too.
There’s more detailed information about growing poinsettias here: extension.umn.edu/houseplants/poinsettia#light-and-temperature .
Written by U of M Extension Master Gardeners in St. Louis County. Send questions to firstname.lastname@example.org .