How to Get a Poinsettia to Turn Red Again
A poinsettia colors when it gets 14 hours of total darkness every night for 8 to 10 weeks. Start around Oct 1 for Christmas. The nightly routine, the ligh...
Published by ThriveThyme
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The Short Answer
A poinsettia turns red when nights are long. Give it 14 hours of total darkness every night and 6 to 8 hours of bright light every day. Clemson Extension says to start the first week of October and keep it up for 8 to 10 weeks. Mississippi State says that from an Oct 1 start, bracts begin to color by late November and the plant should be in full color by Christmas.
The colored parts are bracts, which are leaves. The true flowers are the small yellow buds in the center.
Pick your bloom date on the Holiday Rebloom Desk and it gives your start window and a calendar reminder.
When to Start for 2026
| Bloom by | Start long nights between |
|---|---|
| Thanksgiving, Nov 26 | Sep 3 and Oct 1 |
| Christmas, Dec 25 | Oct 2 and Oct 30 |
These windows count back 8 to 12 weeks from the date: about 8 weeks to first color, and up to 12 for full color. Start at the early date if the day matters.
The Nightly Routine
- Every evening at 5 pm, move the plant into a closet or set a large box over it.
- Leave it in total darkness until 7 am. That is 14 hours.
- Bring it back to a bright window for the day. It needs 6 to 8 hours of bright light.
- Keep it at 60 to 70 F, away from drafts and heat vents. Below 50 F, leaves drop.
- Water when the surface feels dry. Mississippi State suggests feeding about every 14 days during treatment.
- Turn the pot every day so all sides get light.
The Light Leak Trap
This is where most attempts fail. Maryland Extension says even a small light leak prevents flowering, and delayed color is commonly caused by light during the dark period. A garage light, a lamp, or opening the closet door is enough (Mississippi State). Use a closet no one opens, or a box that sits flat with no gaps.
When to Stop
Once the bracts show color, the plant is far less sensitive to light. You can end the dark treatment and treat it like a new poinsettia (Mississippi State). Minnesota Extension ends treatment at Thanksgiving and moves the plant to a sunny spot.
Starting Late?
If you start now, in late October, expect color around late December into January. A poinsettia started after the window still colors, just later. Keep the routine going until the bracts turn.
Will It Work?
It is doable, but it takes steady care. Mississippi State notes that single-stemmed poinsettias do not reflower well and that home plants rarely match greenhouse quality. Plants that were pruned and grown on through summer have the best chance.
Pets
The ASPCA lists poinsettia as toxic to dogs and cats, but notes it is generally over-rated in toxicity. The sap irritates the mouth and stomach and sometimes causes vomiting. See pet-safe plants.
Next Steps
- Plan your plants on the Holiday Rebloom Desk.
- Have a Christmas cactus too? Read why a Christmas cactus will not bloom.
- For a sure bet this year, plant an amaryllis for Christmas.