En EspaŅol

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?


Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
rate this answer
Not Yet Rated

Friday - October 28, 2005

Region: Southwest
Topic: Non-Natives
Title: Hours of darkness for non-native poinsettia to bloom
Answered by: Joe Marcus and Nan Hampton


I have a poinsettia from last Christmas still alive. I was told to get it so many hours of darkness. Do you know how many hours? When would be the best time to start displaying the plant again?


The poinsettia (Euphorbia pulcherrima) is native to southern Mexico. They are "short-day" plants which means that flowering is in response to long nights. It varies among cultivars, but 16 hours of uninterrupted darkness per night for several weeks is sufficient to induce the flowering response in any poinsettia. Any light at all will delay or stop the flowering response. There are classic stories about automobile lights from nearby highways and even flashlights from night watchmen delaying flowering on greenhouse grown poinsettias. People commonly put their plants in a dark closet each night for a few weeks in the fall to induce flowering and the red bract development (they bring them out each day). It is a little late to get your plant to flower by Christmas, but you can still get it to turn red just the same. If you start now, it may be red in time for St. Valentines Day! You can read more about the care of poinsettias.

More Non-Natives Questions

Non-native invasive chickweed in Collegeville PA
December 31, 2011 - My problem is chickweed. I have found considerable information on how to eliminate the chickweed. My question is after following a suggested elimination process: How and when do I reseed with grass?...
view the full question and answer

Problem with non-native bower vine (Pandorea jasminoides)
September 27, 2011 - I live in Temecula, CA I have grown pink bower vines before with great success. I recently purchased 2 bower vines and planted them on each side of a trellis in full sun. They flower but do not grow...
view the full question and answer

Insects on hybrid 'Ann' magnolia in Morrow OH
June 17, 2010 - I have an Ann Magnolia. It is covered in all kinds of stinging insects and flies. This has never happened before. Is this a common problem for the tree? What should I do?
view the full question and answer

Care for non-native Easter Lily (Lilium longiflorum)
June 07, 2005 - How do you care for an Easter Lily once the flowers have fallen off?
view the full question and answer

Did Mexican fire bush (Hamelia patens) survive winter cold?
May 05, 2010 - I have a Mexican fire bush that I planted last spring and it bloomed beautifully last summer. It browned and we cut it back to the ground. Right now it's showing no signs of life and I'm afraid it m...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2015 Lady Bird Johnson Wildflower Center