Explore Plants

Share

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
    
 

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

Wednesday - December 02, 2009

From: Marble Falls, TX
Region: Southwest
Topic: Cacti and Succulents
Title: Potted crown of thorns cactus cold tolerance in Marble Falls, TX
Answered by: Barbara Medford

QUESTION:

I have a large potted crown-of-thorns cactus. Can it remain outside this winter in the Texas Hill Country?

ANSWER:

When we originally received this question, we went to our Native Plant Database and found Koeberlinia spinosa (crown of thorns), which grows natively in far South Texas and the Big Bend area, where temperatures are warmer than they are in Central Texas; however, this plant is known to be hardy to 0 deg. F. So, we replied that we thought the potted plant would be all right outside. Turns out we let the common name curse keep us from finding the plant actually referred to in the question. This old-fashioned houseplant, Euphorbia milii, crown of thorns, is more likely the plant about which the inquiry was sent. 

The Lady Bird Johnson Wildflower Center is dedicated to the use, care and propagation of plants native not only to North America but to the area in which it is being grown. This puts this native of Madagascar our of our realm of expertise. We can tell you that while we said the Koeberlinia spinosa could be wintered over outside in a pot in the Hill Country of Texas, we find that the Euphorbia milii is only hardy from Zones 9b to 11. Central Texas is generally Zone 8a. The plant itself would be threatened by a hard frost in this area, and certainly a plant with its roots exposed in a pot would be even more likely to be damaged by cold weather. Euphorbia milii should be treated as an indoor potted plant over the winter. Here is more information on this plant from Floridata and pictures from Google

One further note: neither the Koeberlinia spinosa nor the Euphorbia milii are cacti. Koeberlinia spinosa is a member of the Capparaceae or Caper family, while Euphorbia milii is a member of the Euphorbiaceae or Spurge family.

 

More Cacti and Succulents Questions

Wholesale dry yucca trunks and branches from California
January 29, 2012 - Where can I buy wholesale dry yucca trunks and branches? I have spent the last hour looking for them and can only find nurseries and decorative branches.
view the full question and answer

No blooms on Spineless Prickly Pear in Austin
June 07, 2012 - I've had a spineless prickly pear planted in the shade for about 3 years. It has done just fine there, but has never bloomed. I recently moved it to a full sun location(I'm in north Austin) and cove...
view the full question and answer

Debugging and Preserving Dried Cholla Cactus
January 04, 2014 - Hi. Recently found an intact skeleton of a cholla cactus. I want to Bring it in our house. Are there any dangers associated with this, like bugs inside the "branches?" how would you suggest I prese...
view the full question and answer

Native plants of Taos and Los Alamos NM from Houston
April 07, 2012 - Hi, Mr. Smarty Plants, can you recommend a guidebook for the native plants of the Taos/Los Alamos region? (I'm most interested in forbs.) I'll be headed there in May--is there anything I should es...
view the full question and answer

Source for Century Plant in Wilmington NC
June 24, 2012 - Where can I buy a Century plant in the Wilmington NC area?
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.