En Español

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

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

rate this answer
3 ratings

Thursday - April 20, 2006

From: Kansas City, KS
Region: Midwest
Topic: Trees
Title: Inadvisability of mounding earth around tree in ring
Answered by: Joe Marcus


We have a mimosa tree in our backyard. My husband wants to build a tree ring around it. My mother told me that some trees will die from having soil built up around it like that. Will a tree ring kill our mimosa tree?


This is one of the more controversial topics in arboriculture. Some arborists swear by tree rings, others say they're useless and, worse, detrimental to the trees. I take a moderate stand on this. In my opinion, tree rings are useful for two purposes: providing a temporary aid to watering a tree after transplanting and protecting the crown of the tree from lawn equipment.

The old donut watering dike that we've all seen for many, many years has recently morphed into a mound of earth around the base of the tree. I have seen these as much as 1 foot in depth! These mounds do no good and actually can do great harm. Soil and mulch mounded against the trunk of a tree can harbor both harmful insects and pathogens and provide the perfect environment for them to gain entry to the base of a tree. Moreover, some trees seem to have some critical gas exchange happening at the base and certainly depend on oxygen at the roots. A thick mound of soil over the root ball greatly diminishes the volume of gases available that are critical to the health of the tree.

Watering rings (the donut mounds) should be built outside the hole dug for the tree, not on top of the root ball as they almost always are constructed. They're really not necessary if the tree owner will spend six minutes watering their newly transplanted tree at low flow rather than two minutes with the hose gushing at full pressure. Little sprinklers running at low pressure do a great job of watering new trees.

Some people maintain rings or bare earth or loose mulch around their trees as a way to protect them from mowers and weed trimmers. This is in general a good idea as mechanical damage to the base of a tree is often the source of serious problems far into the future. However, care should be exercised not to mound soil against the trunk of the tree or to smother the roots. For small trees, I like to use curved clay tiles or bricks as a physical barrier around the base of the tree. Grass can grow right up to (and into) the barrier which I can mow up to. If grass or weeds pop up between the barrier and the tree it's a simple matter to remove the tiles or bricks, pull or trim the grass and replace the barrier. If the barrier is not placed directly in contact with the base of the tree insects and diseases won't have any better chance of getting started than if it weren't there at all.


More Trees Questions

Non-flowering mimosas in Texas
July 08, 2008 - I have two mimosa trees, about 3 years old. Both were grown from volunteer seedlings. Neither have flowers nor have they produced seed pods. Are they too young or do they need a source of pollenation...
view the full question and answer

Survivability of birch trees in Texas
August 16, 2006 - Is it known whether Gray birch (Betula populifolia Marsh) will grow in North Texas? It seems like the only birch variety which might - and how short is a "short lifespan" for a tree?
view the full question and answer

Can hackberry twigs and leaves be safely used in compost?
March 05, 2009 - If Hackberry trees and leaves have growth inhibiting compounds, should they not be used in compost piles?
view the full question and answer

Native plants for city lot in Longview, TX
March 19, 2008 - Just bought a city lot in Longview, TX and want to put in some plants at the periphery even before the house is built. Can you recommend any that would be from your list of East TX plants that are pa...
view the full question and answer

Huisache blooms when freeze is over
May 02, 2005 - I live in San Antonio, TX and have heard that when the Huisache blooms all danger of frost or freeze is over. Is that true? And, this year to date (April 22, 2005) we have not seen the Huisache bloo...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2016 Lady Bird Johnson Wildflower Center