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 - June 10, 2011

From: Loveland, CO
Region: Rocky Mountain
Topic: Trees
Title: Are junipers tainting the soil in Loveland CO?
Answered by: Barbara Medford


Have several varieties of junipers around my yard. Each year I try to place a small garden in a corner of my yard, the plants don't do well at all. Growing up nearby, I gardened with my parents so I have a good basic knowledge of gardening. When we were at Travis AFB in California I found out that the eucalyptus tainted the soil. Do junipers do something similar? Thank you


We did some research and discovered no instance in which eucalyptus, which is native to Australia and therefore out of our range of expertise, poisons soil. We did, however, find this article from the U. S. Fish and Wildlife Service Environmental Containment Program Eucalyptus Trees Used to Clean Up Selenium in California. Since you say you were in California, perhaps this is what you heard about.

So far as we know, neither does any member of the Juniperus genus poison the soil around it. We don't know which members of the genus you have, but the ones native to Colorado are: Juniperus communis (Common juniper), Juniperus communis var. depressa (Common juniper), Juniperus monosperma (Oneseed juniper), Juniperus osteosperma (Utah juniper), Juniperus scopulorum (Rocky mountain juniper), and Juniperus virginiana (Eastern red cedar). You can follow each plant link to our webpage on that particular species of Juniperus, and read the information about its use and care.

The next question is: Are you trying to plant that garden under those junipers? From a previous Mr. Smarty Plants answer:

"As for the Juniperus ashei (Ashe's juniper) on your property, there is some disagreement whether anything will grow under them. Again, you have the heavy shade, and the litter of needles, berries and twigs always on the ground, which will discourage many plants and inhibit seedlings. 

From this article  Biology and ecology of Ashe Juniper by F. E. Smeins and S.D. Fuhlendorf, we extracted this paragraph on the allelopathy of the Ashe juniper:

'There is little evidence that the accumulated litter of Ashe juniper in any way alters the chemical nature of the soil as it relates to growth and development of other plants (Yager 1993). Soil chemical and physical properties are in fact "improved" by the presence of the juniper litter (Marshall 1995). No allelopathic effects have been shown to be produced by the litter. The major impact of the litter seems to be its physical presence and its alteration of hydrologic properties of the area under the canopy. The thick litter layer is a difficult physical medium for seeds of other species to germinate and grow in mainly because moisture either runs off (due to the hydrophobic nature of the litter) or it dries out very quickly after a precipitation event, which prevents seedling growth from reaching the mineral soil (Yager 1993).'

'Junipers create an environment under their canopy.' They do indeed. That environment includes dense shade and a lot of shed material like leaves, berries and bark (aka mulch).  Add to this that the shed material is hydrophobic ( it sheds water rather than absorbs it) and I ask you what could be less conducive to existing plants?"

You need to till the litter from the junipers and oaks into the soil and plant natives appropriate for your area, soil, light, drainage and enjoy. The juniper is considered a nurse plant for many plants that grow below it and bask in the conditions.

Now, here is the catch-did you note we said "plant natives?" If you are trying to grow plants not native to your area of Colorado, you may be blaming the juniper for something that is not its fault.




More Trees Questions

Pecan leaves falling off the trees in Austin, TX.
August 08, 2012 - Why are the pecan tree leaves turning black, sappy and falling off the trees, in great quantities? This has happened since the recent rains, all through the Allandale area.
view the full question and answer

Trees for privacy and filtering dust in NY
March 23, 2011 - I live on a very busy, DUSTY, dirt road in Putnam County NY. (zip code 10524) What is the best, fast growing evergreen that I can use for dust control and privacy? I would prefer something that requi...
view the full question and answer

Small flowering tree for Burbank IL
April 14, 2010 - Looking for a semi-dwarf flowering tree resistant to disease and insects. Current flowering crab has fire blight. What would you suggest planting. We live in a Chicago IL suburb.
view the full question and answer

Propagation of maple tree in Canada
July 08, 2008 - I have a gorgeous maple tree in my front lawn and I want to plant more like it. The tree gives off very few keys a year so I want to make sure this works. How do I go about planting a maple key?
view the full question and answer

Colorful Maples for Virginia and Pennsylvania
November 27, 2015 - We are trying to find out which trees have three or more leaf colors in the fall in Virginia and/or Pennsylvania. We found that Sweetgum and some maples do. Can you please let us know which maples hav...
view the full question and answer

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