Now that you have enjoyed your poinsettias through the holidays, many people ask how to bloom them again next year. It can be done, but you need to know right up front that the plant isn't likely to have as large and beautiful bracts (the colored leaves) as it did this year. The techniques and conditions used in commercial production are beyond the scope of the average homeowner without a greenhouse. Bringing the bracts into color requires following a rigid schedule beginning the first of October and continuing until the bracts color, which may be ten weeks. Missing the schedule just one day or altering the conditions even slightly may undo all the earlier work. That said, here is how to rebloom a poinsettia.
After the holidays, maintain the plant indoors until the night temperatures outdoors reach 60º. There are two options for maintaining the plants: You can either treat your poinsettia as a houseplant or store it in a dormant state. If the plant is still gorgeous (many of the new cultivars will stay that way long into the new year) you can maintain it at normal home temperatures as you would a houseplant. Be sure it has your sunniest window. Give careful attention to watering, keeping it barely moist and do not allow the soil to become soggy. Feed with a houseplant fertilizer such as Bachman's Excel Grow at the recommended rate about every two weeks. In late March or early April prune the poinsettia back to 6-8 inches tall. Just before you put it out for the summer, you should repot it (described below).
If you choose to store the plant in a dormant state, reduce the water until the leaves dry and fall off, then put the plant into an area where it will receive minimal light (it does need some) and temperatures between 55-60º. It must not be over 60º or the plant won't stay dormant. In late March or early April, cut the plant back to 3-5 inches tall and repot into a slightly larger container. If there is more than one plant in the pot, give each its own pot slightly smaller than the original it shared with the others. You have too much effort invested to compromise the roots, so use a good, porous, professional potting soil such as Bachman's Exceloam. Water well and, when the new growth begins, start feeding as mentioned above.
Poinsettias should be grown outdoors for the summer. They need to do this to take advantage of the higher light levels available outside. Place them where they will receive at least 6-8 hours of direct sun daily. Protect them from the hottest of the afternoon sun if they are sitting on a masonry patio or other reflective surface. This isn't necessary if they are in a flower bed. Potted plants can be sunk into the ground to help keep them stable, cool and moist. If the pots are in contact with the soil, remember to turn the pots or lift them up each week to prevent the plants rooting out through the drainage holes. Roots will grow out of the holes whenever they get the chance and then you will shock the plants when you break the roots to bring them in. Increase the fertilizer applications to weekly. In late July pinch the plants (remove the growing tip and the upper 2-3 leaves on each stem) to keep them stocky and well branched. In early fall, when the night temperatures are starting to dip into the 50s, bring the plants in. Again, give them the sunniest window and continue to water as needed and fertilize regularly. Now you must make your plans to carry out the schedule that will cause the bracts to color again.
Starting Oct. 1 the poinsettias must be kept in the dark from 5 p.m. until 8 a.m. Then they must be put back in bright light for the day. The night temperatures should be between 65-70º and the daytime temperatures can be 70-80º. However, they need a 7-10º difference between the two, so you cannot keep them a uniform 70º. Continue the normal feeding and watering practices that have been established. This program needs to continue, without interruption, until the bracts have begun to color, usually until Thanksgiving, at least.
Deviation from any part of this schedule can result in delayed flowering or no flowering at all. The dark treatment is usually accomplished by putting the plants in a closet that will not be opened accidentally or under a box that has had the inside painted black (dried well, no fumes). Leaving them in an unused room is chancy since stray light from street lamps, passing cars, porch lights or accidentally opening the door can undo the work.
After the bracts have begun to color, you are still not home free. The plants still need to have 6-8 hours of full sun or the equivalent from high intensity lighting until the bracts are completely colored. When that has happened, you should stop feeding the plant to prolong bloom and can place it where you would like to display it for the holidays.
A Quick Overview For Reblooming Poinsettias
January thru May
Provide strong light all day and keep it barely moist.
Fertilize every two weeks.
Prune to 6-8 inches tall around April 1
June thru early September
Move the plant outdoors.
Provide 6-8 hours direct sun. Keep moist.
Fertilize every week.
Take the plant indoors.
Provide strong light all day. Keep moist.
Fertilize every week.
Early October thru Thankgiving
Days: strong light - keep moist - keep warm.
Nights: complete uninterrupted darkness - cool.
Continue fertilizing weekly.
As soon as the bracts develop some color, discontinue day/night treatment.
Provide bright light. Keep moist.
Quality Bachman's Grown Poinsettias
Exceloam Potting Soil
Excel Gro Fertilizer
Containers and Saucers
Gardening Books and Information Sheets
© Bachman's 1999
Author: Mary Henry and Margaret Purcell, Horticulturists