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 ixora full of weeds in Miami FL
July 29, 2011 - My Ixoras are full of weeds look like some kind of berry. Is there a way to get rid of them?
view the full question and answer

Caring for non-native Peace Lily
July 04, 2005 - I have given my closet plant too much miracle gro and the leaves are drooping really bad. What do I need to do?
view the full question and answer

Camellia seeds
September 21, 2008 - Hi Mr. Smarty Plants; I have a Camellia plant that has bulbs that look like they could be fruit. And when this bulb opened, four or five little nuts came out. Are they fruit or nuts and can they be e...
view the full question and answer

Yellowing leaves on non-native jasmine from Austin
June 25, 2012 - Hi, I have a mature jasmine plant in the ground in a very sunny courtyard which gets watered daily. The lower leaves are turning yellow and am wondering if this is too much water for it. The top lea...
view the full question and answer

Problems with non-native Carrotwood tree in Toluca Lake CA
June 25, 2009 - My Carrotwood tree leaves are turning yellow and curling down, Why? Also due to a bad trim, the outer limbs are dying. Can you tell me what is wrong? It is an old tree and I would like to save it!
view the full question and answer

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