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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Sunday - March 17, 2013

From: Round Rock,, TX
Region: Southwest
Topic: Compost and Mulch
Title: Use of free cedar mulch in Round Rock, TX
Answered by: Barbara Medford

QUESTION:

Round Rock provides city residents free mulch to pick up. It is all cedar apparently. I am turning my now dead, mostly clay, very alkaline and rocky thin soil front lawn into a bigger flower bed of mostly Texas natives for butterflies and birds. I'm expanding a flower bed into the lawn to do so. I have a 20 year old bed of blue mist flowers the butterflies love and flame acanthus that hummingbirds love. I've added Damianita, Blackfoot Daisy, Rudbeckia, Frog Fruit, Skullcap (may not be native), Aster, Butterfly weed, and I also have already some antique roses into the lawn area and around the porch. Question: I want to use this free Cedar Mulch all around the new native plants on the lawn. I put a couple of layers of newspapers down, then a 4" thick layer of cedar mulch. Is that too thick? Is cedar mulch OK to use on a native Texas plant bed? I know you usually don't answer about roses, I have also mulched around a Mutabilis rose with the same cedar mulch. Perhaps a friend can answer that one. The mulch is already dried and on its way to decomposition, not still green, but it does have a few big sticks in it still. Any advice appreciated. Thank you so much for the service you provide!

ANSWER:

Before we do anything else, let us congratulate you on your largely native-to-Texas garden you have been nurturing, apparently for many years. We are very tempted to say "whatever you have been doing, keep doing it." You obviously have also been choosing plants native to Central Texas, which can sometimes be a challenge with its alklaline, rocky soils.

To address your actual question, we are always in favor of using natural mulch, including that of shredded Juniperus ashei (Ashe juniper), better known around here as "cedar."  We are glad that cities are beginning to dispense this excellent mulch and discouraging burning cut-down Ashe junipers. You might be interested in this previous Mr. Smarty Plants article about using the wood ash from junipers to spread on the ground. Next, we suggest you read our How-To Article Under Cover with Mulch.

This article definitely emphasizes the many advantages of a shredded mulch, but also mentions some concerns, with which we agree. For some time, there was some discussion back and forth over the possibility of overdoing the mulch. One problem is that too much mulch around the roots of the plants can shelter insects that could be chewing on that plant, and may even promote mildew, which you don't want going on, especially on your (non-native) roses.

Another problem, chlorosis, might crop up if you have too much mulch around the roots. Please read yet another previous Mr. Smarty Plants answer (we are pretty lazy and don't like saying the same thing twice). That particular article is on Sophora secundiflora (Texas mountain laurel), but the same problem could apply. Also in that previous answer is a link to a university article on the process of chlorosis, itself. We hope you will read that too.

Summing up: We like what you're doing, and we know free mulch is very tempting, but you should watch out for some of the problems we have mentioned, and maybe back off a little on the depth of the mulch.

 

From the Image Gallery


Ashe juniper
Juniperus ashei

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