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

Tuesday - May 15, 2007

From: Austin, TX
Region: Southwest
Topic: Cacti and Succulents
Title: Root depth of opuntia
Answered by: Nan Hampton


What can you tell me about the depth of roots of the opuntia? Does it vary with different varieties or is there formula to estimate the depth according to the mature size or to the culture - garden soil - wet or dry - etc ?


As far as Mr. Smarty Plants knows, there is no magic formula to determine the depth of the roots of Opuntia spp. In general, the Opuntia cactus have tap roots with extensive shallow lateral roots. The size of the tap root and the lateral root expanse has to be correlated, to some extent, with the plant's age and size; however, environmental factors, such as abundance of water, soil temperatures, and CO2 concentration, also have a large effect on tap root depth and lateral root extension. For instance, a study of certain Opuntia species naturalized in Africa has shown that water stress increases the length of the tap root and reduces the size of lateral roots. In Opuntia ficus-indica increasing soil temperatures and CO2 concentrations cause the lengthening of tap roots.

You can read more about cactus survival strategies.



More Cacti and Succulents Questions

Large agave (century plant) flower stalk
June 17, 2008 - HI.I live in Blythe, Ca. and have a GIANT of an agave in my back yard. It is now over 40'high and is blooming. I first noticed the stock growing at Easter when it was about 12' high. It is now t...
view the full question and answer

Controlling Cochineal Insects on Cholla Cactus
July 07, 2011 - We have cochineal insects on a cholla cactus. Will they kill the plant? What should we do to get rid of them if water spraying them won't work?
view the full question and answer

Black rot at center of Agave from Clovis CA
May 12, 2013 - We have some beautiful variegated "Green & Cream" Agave plants in our cactus garden. One in particular has done quite well for several years and is the largest, about 18" tall & across, it has neve...
view the full question and answer

Puncture wound from Blue Agave leaf.
October 19, 2015 - A blue agave leave went through my glove and into my hand. It's swelled up a bit and hurts. Is this just a passing thing.
view the full question and answer

Cleaning up Adams Needle yucca in Vancouver Island BC
May 19, 2009 - We have Adam's needle yucca's in our the flower bed of our newly purchased home here on Vancouver Island BC. They thrive and produce impressive flowers. How do I clean them up in the spring time ...
view the full question and answer

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