Pine Bark - Bad Mulch Choice Newsletter
Q: I think it would be good to have an answer about why pine bark gets an F, in your estimation. I know why, I think, but a published explanation might be helpful to your readers.
A: OK. First, it doesn't behave itself - wont stay in place. It washes and blows around. When it does stay in place, it's not very good for plants. As pine bark breaks down, some rather nasty natural chemicals are released - such as phenols and terpenes that outgas and damage biological activity in the soil. These chemicals are basically antimicrobial. That works fine while on the tree trunk but not well in the soil.
Pine bark is used widely as a bed preparation material but should not be. The fine and medium sized products are the worst choices. Very fine particles of pine bark mulch can rob nitrogen from the soil. The large size deco bark is a fair mulch to use for shrubs and ground covers. The large chunks stay in place a little better and allow air to flow around the large pieces and down to the soil and to the plants’ roots. But, there are much better choices.
The best mulch to use is shredded native tree trimmings. Ground up trimmings straight from the tree care company’s truck are a perfect balance of carbon from the wood and bark along with protein (nitrogen) from the flowers, fruit, buds, stems, cambium and green leaves. Some people object to the coarse texture but the horticultural aspect is perfect. Not only is the product a perfect balance of carbon and nitrogen (C:N), the shredded texture functions to hold the mulch in place even on slopes. Shredded cedar is available and is really an excellent mulch but a shredded mix of trees types and bushes is even better. Variety is the spice of life! Some compost companies regrind and partially compost the product to produce a more visually pleasant look but the raw product works just as well or better.
P.S. Pine bark is better than no mulch at all – but barely.
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