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Dallas Morning News - November 7, 2019

Mulches – Why Shredded Tree Trimmings Are Best


Bare soil is a bad thing so any natural mulch is better than no mulch - so why am I so negative about some mulches and positive about others, especially shredded native tree trimmings? Let’s review the negatives about the poor and so-so choices first.


Shredded native tree trimmings are excellent even if some large pieces need to be removed

Shredded native tree trimmings behave and stay in place 


Shredded rubber tires claim the position of absolute worst choice. They hold heat but not water and don’t stimulate beneficial microbes. Plastic sheets and weed blocking fabrics don’t control weeds well and plant roots are damaged from heat buildup. Plastic also fouls up the flow of oxygen in and carbon dioxide out of the soil.


Second worst choice is ground up and then dyed lumber. You probably know this stuff as the ubiquitous black and red mulch. It’s horrible. Chemical contaminates are one issue but more importantly these ugly mulches are nothing but ground up wood products - mostly cellulose made of carbon and contain no protein, a source of nitrogen. This imbalance of carbon to nitrogen causes nitrogen drafting from the soil and yellow plants unless lots of fertilizer is used.


Pine bark, especially the fine textured material, won't stay in place

Pine needles are much better than pine bark


Third worst choice is pine bark. It has a bad habit of blowing and washing away. Besides not behaving and staying in place, natural chemicals such as terpenes, although helping protect the tree when on the trunk of the tree, are quite harmful to the beneficial life in the soil.


Shredded native tree trimmings can be from a mixture of tree types


Shredded native tree trimmings are also good for paths in the vegetable garden and in the landscape


Cypress that is not high on my list because it doesn’t break down well. We want mulch to decompose. That's what creates the true natural food for microbes and plant roots. There’s also an environmental issue of harvesting depleting the native wetlands.


Pine needles makes good mulch but look a little out of place when used on property with no pine trees. Pecan shells are so-so but also move around too much and fresh shells can attract fire ants. Lava gravel is the only gravel that works well for mulch. It works almost as well as plant based mulches and helps to keep the neighborhood cats out of the beds. Shredded hardwood bark is a good choice. Like the shredded tree trimmings, it stays in place well, looks good, smells good and breaks down properly.


Shredded hardwood bark makes quality mulch

Shredded cedar makes excellent mulch for all plants


The best mulch is recycled woody plant material. Our native cedar is one of the best choices. It stays in place, breaks down well, provides fragrance, repels insects and feed soil microbes beautifully. All parts of all cedar trees make excellent mulch. A mix of tree species in the shredded mulch is also just fine.


Some companies grind the rough textured shredded tree trimmings into a finer texture and even add compost. That makes prettier products but the material right out of the tree care company’s grinder is fine for all plantings other than very small transplants. I use compost for them.




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