Step by Step Instructions and Timing for Getting
Poinsettia to Bloom Again
Getting poinsettia to bloom again is not complicated but it does demand specific cultural
controls with little room for error.
We'll assume you've grown your poinsettia since last Christmas and you've fed it
properly with lots of light - it has grown into a small shrub and you want to get it to
bloom again.
Here are the guidelines for successful growing of this plant you'll need to understand
these as well.
1
Poinsettia Is A "Short Day" Plant - Technical
Poinsettia are referred to as "short day plants" and they require a night time (lack of
sunlight) of 11 hours and 45 minutes to initiate flowering.
So as our summer days shorten towards fall, the increasing length of night triggers
flower formation.
This assumes a temperature of 65F.
If the temperatures are lower (say 62F) then the time of sunlight deprivation will be
longer - in this example 13 hours of night.
Cooler temperatures will require longer nights.
And temperatures above 70F will create a similar situation - too high a temperature
requires longer night hours.
The amount of darkness per night a plant needs to bloom depends on the temperature.
The 12-Hour Rule Of Thumb
Generally, in the home environment you need night darkness of 12 hours for good and
fast flower formation.
And you require this night darkness for approximately 6 weeks starting in midSeptember. After this, you only require regular day length (whatever that is in your
location)
How Much Light Will Ruin This Project?
If you put lights onto the poinsettia leaves (even for a few seconds during this 6 week
period) at night -photosynthesis will start and the plant will "wake up" and the dark
requirements will not be met.
Research shows that light as low as 1-2 foot candles will trigger growth. There is some
data indicating a few seconds of light will put the plant back a hour or more.
(As a sidenote -this is why some greenhouses in urban areas can no longer grow
poinsettia. Traffic moving past the greenhouses at night throw headlight beams onto the
plants and wake them up and street lights can be a major problem if they don't use
artificial shading on the plants.)
This means if you walk into the back bedroom where you're growing this plant, flip on
the light to see something - your plant will start growing and that night's darkness is
screwed up. It only takes a second of light to mess it up.
This Is A Southern Plant - How To Grow
Getting a poinsettia to bloom again requires full, bright sunshine. Anything less
will reduce flowering. In the home, this translates to a full south window (squeaky clean)
or supplemental grow-lighting. Low light levels will also produce small bracts.
Soil should be a high quality artificial mix. No garden soil as the soil has to be welldrained.
House temperatures should be in the 65-70F range during the night and 80F during
the day for best flowering.
Grower Trick
I hate heating an entire room or house just to grow one or two small plants. I found if
you use a heating mat (normally used for propagation) and sit the pot on it, you'll get
good results.
You heat the roots and this seems to work just as well as heating the entire plant.
Screw up the temperatures and the plant will not flower.
Feeding Poinsettia
Commercial growers feed with every watering in dilute concentrations but home
gardeners can get their poinsettia to bloom again by feeding a balanced houseplant food
once a week at full strength.
Failure to feed will produce tiny bracts.
Humidity Is Good
Maintain a high humidity for the plant if possible. Keep feeding.
Pruning - Important
Getting a poinsettia to bloom again means proper pruning as the plant sets a bloom
better on new growth than old.
The second week of September, cut all weak and spindly growth from the plant and
pinch the remaining growing stems to leave 4 to 6 leaves or leaf nodes per stem or
branch.
On short plants, you can simply leave 4 -6 leaves to survive and top cut the rest of the
plant off.
Third week of September. If warm enough and growing strongly the poinsettia
should throw shoots and by the third week of September, those shoots should be oneinch long.
Third Week September Onwards
After the third week in September, your job is to watch the temperatures, night light
and feeding. It's major growing time!
Keep feeding and watch for insects. It is at this point that whiteflies attack poinsettia
and you can control them with soap only until the color starts to show on the bracts. If
you spray soap on colored poinsettia leaves, they do not respond well (burning). Other
common pests include mealybugs and thrips.
When Do I See Color In My Poinsettia?
If you maintain the temperature, full light environment, watering and feeding, you
should see color by the middle of November.
Any deviation from the guidelines above and flowering will be delayed.
If you don't see color, you've messed up somewhere.
The Overall Schedule
This is the overall schedule for when you should be doing things to the plant.
January through mid-September - grow Poinsettia in full sunlight, feed at least once
a week and water when needed. It can go outside during the frost free summer but
when night temperatures start to dip, bring it indoors.
Mid-September - prune back as above
Mid-September - begin temperature regime as above
Mid-September - 12 hours of darkness and 12 hours of full sunshine as above for at
least 6 weeks
End October - can go into full sunshine all day long
Middle November - you should start to see color in bracts