Question
QUESTION: We recently started a project replacing our landscape bark with limestone and was told this will cause problems with our plants, flowers and trees. Is this correct and if so would it work to remove the rock 6-10 inches from the root area? We liked the color with our brick and have a large project that is now 1/2 done. Thanks for your help, Sheryl

ANSWER: Hello,

Stone mulch absorbs heat and the surrounding soil will get somewhat warmer,but there does not seem to be any reported instances of serious damage occuring from this. Of course,a darker colored stone will absorb more heat than a lighter colored stone mulch. The lighter colors reflect heat. Reflected heat can be a problem on surfaces such as parking lots or roofs but once again I do not know of any problems with stone mulch.

Limestone is sometimes added to soil to increase alkalinity but I would not think that enough of it would leach out from your mulch to greatly effect your soil pH.

As long as you do not exceed a depth of a few inches,the mulch will not harm your plants around the root zone. An interlocking (a stone mulch that has narrow spaces between the individual pieces) would not be a good idea around the root zone. This will impede water and air penetration to the roots. Angular cut pieces are more interlocking than round cut pieces. Good luck. Let me know if I can be of further help.

Mark Harshman
http://www.harshmandrafting.com

---------- FOLLOW-UP ----------

QUESTION: I'm still concerned about our Evergreen type trees as they like an acidic soil?? Thank-you! Sheryl in NW Iowa

Answer
Hello,

I do not think that the small amount of lime that may leach out of the mulch will affect your trees. If it would give you peace of mind,keep the limestone mulch outside the root zone. Do a soil pH test. I would also advise you to get a second opinion about this from someone knowledgeable in horticulture. Your state extension agency may be able to help.

While it is true that evergreens prefer an acidic soil,most plants tend to grow close to the neutral pH range. One particular example of a plant that is particularly sensitive to soil pH is azalea,which requires an acidic soil. Good luck. Let me know if I can be of further help.

Mark Harshman
http://www.mahdrafting.com
Email: [email protected]

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