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Mulches – the do’s and don’ts

I love winter mulches for many reasons. However, I dislike some of the current mulch types and practices that are not only ugly, but dangerous and unsustainable. I will start with the ugly and then move to the superior choices.

Both dyed mulch and rubber mulch are hideous. You might see these used at fast food joints that hire uninspired, low-bid landscapers to do their artificial-looking landscapes. Dyed mulch is sometimes made from old pallets, decks or containers that have been treated with chromated copper arsenate (CCA) once used as a wood preservative. This mulch can be unsafe for humans, soil, plants, and animals. The use of CCA was banned in 2002 but old woods continue to be used. Today, to be certain it is safe, dyed mulch should be certified by the Mulch and Soil Council (MSC).

Rubber mulch is made from recycled tires. This material is toxic due to the chemicals that leach from the tires. These include heavy metals and a host of hazardous chemicals which are dangerous to both humans and the environment. To me, it is unnatural having shredded rubber mulch in a garden.

My number one choice for a winter mulch is shredded dry leaves gathered from the garden. One reason to shred the leaves is that they are more attractive and will break down easily, thus becoming an important nutrient source for the plants. I like to wait until the plants are dormant and then apply around 2 to 3 inches of my mulch around the garden. This mulching acts like a soil blanket as it helps insulate the roots and protect them from drastic temperature changes. A good organic mulch enhances soil quality as it gradually turns into a rich humus. Humus will help soil tilth as well as provide nutrients along with beneficial microbes. Mulch can assist in preventing weed seeds from germinating as well as holding in moisture during dry periods.

Small bark nuggets or small wood chips are also excellent mulches because they add soil nutrition as they break down. The most attractive and finest hardwood mulch is triple-shredded bark. Single shredded has long strands, around 9 inches, and looks coarse. Double shredded mulch, the most frequently used, has 4 to 6 inch strands. Using a variety of mulches is a good idea and can depend on what is available and affordable.

The Do’s

- consider mixing shredded hardwood bark and small bark nuggets for a mulch. It is attractive and can be used on slopes helping prevent erosion

- if your plants like drier soils, such as lavender, thyme, or rosemary, try using small pea gravel or chicken grit (sharp granite pieces) as a mulch

- pine needles are excellent for woodland gardens and areas where acid loving plants are growing (such as azaleas)

- cocoa hulls are a great mulch, they give off chocolate fragrance, but beware, they can be poisonous to cats and dogs and can blow in the wind

- use good compost as a mulch as long as it does not have weed seeds in it

The Don’ts

- don’t use more than a 3-inch layer of mulch, 1-3 inches is recommended

- mulch should never be up against the trunks of trees, keep it at least 3 inches away from a trunk

- never make mulch volcanos around trees; these are created when woodchip mulch is piled high and thick around a tree trunk giving it the look of a volcano. The area around trees should be at ground level

- avoid placing mulch right on the crown (growing points) of perennials

- keep soil bare in areas where you want seeds to germinate

- fresh wood chips do not make a good mulch because they take nitrogen from the soil as they are breaking down – once composted they are fine

- long term use of hardwood mulch can cause manganese and other elements to build up to toxic levels

Mulch will give your garden a finishing touch along with providing a host of other benefits. Working in the garden in winter will provide a great head start for your spring gardening chores.


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