Thursday, June 7, 2012

Mulch? This is not Mulch!

Mulch is, and should be, a critical part of your gardening routine.  The material  I have seen used to mulch with can be quite variable: Bark, wood chips, leaf mold, compost, buckwheat shells, cocoa shells, crushed stone, shredded rubber tires, colored rubber mulch, colored chipped wooden shipping crates.

Six inches of mulch smothering a plant
I am not joking about some of those items!  You might be surprised to learn how much poor quality mulch is currently available.  The demand continues to grow and outstrips the supply of quality mulch.

Adding mulch is critical to suppress weeds, keep moisture in, keep soil temperature even and it should add organic material to the soil.  The organic material, with the right balance of nutrients and water is what gives you plants.  For organic material to be useful for growing plants, it must break down to elements that can be utilized by the root system.

Above and below are some images of that recycled and artificially colored stuff.  When it goes down it may look nice and fluffy, but after a good rain all the small fluffy particles disappear, and you are left with a bunch of chunks of wood, colored an unnatural color.  

Gas Station mulch
The problem with this mulch is that it does not break down easily.  It needs nitrogen to aid in its decay, and it will steal it from the soil and significantly decrease the nutrients available for your plants.  The result is poor plant growth and flowering, as well as a yellowing of leaves.

Always talk to your landscape contractor or nursery to determine the source and contents of your mulch.  Remember that anything you add to your garden will effect the health of your plants in both a positive and negative manner, and sometimes you need to balance out what you add.  To help the mulch break down, in the late summer I will often apply some Dried Blood.  This product is pure nitrogen and is a critical element to aid decomposition.  It is also an important product to help green up plants that have turned a little yellow from chlorosis

Of the natural bark mulches, Hemlock has the best red/brown color.  Often times it will be blended with Pine, Spruce and Fir bark which will give it a more brown color.  Pine, Spruce and Fir mulch is a medium brown color, and it tends to to be fluffier and more interwoven with the bark fibers.  Both of these natural bark mulches will partially breakdown over the season, and any leftover should be removed in the Spring before more mulch is added.  If you don't remove old mulch that hasn't broken down, it will continue to take nutrients from the soil to help in its own decomposition.  A tip for this mulch, give it a refreshed look in mid-Summer by using a hard/bow rake and loosen up and mix the mulch.  This will also help it to break down more easily.

The 'Black' mulch that a lot of people use is an excellent choice because it is well on its way to decomposition into useful organic matter.  This mulch is aged and can have all sorts of aged wood chips, bark and organic matter.  Beware of contractors and nurseries that use dyed 'Black' mulch.  This mulch may not be aged at all and may consist of the same materials as the previously mentioned mulch, just colored black.

I prefer a good aged black mulch on shrub and tree beds, and good compost or leaf mold around perennials.  I find it hard to differentiate between the two colors, and it is a truly natural look.  If you are partial to the red or brown mulch, just make sure you are buying a natural and not processed product.  If you do add wood mulch around perennials, be careful not to smother them.  Add just a light layer of no more than an inch.

Some companies will produce their own mulch with the proper blend of materials to ensure good decomposition and ultimately usable organic material for the soil.  Ask about these products and they will gladly tell you more than you could possibly want to know. Hartney Greymont is an excellent local arborist that will help to manage all aspects of your garden and they produce a super mulch.

Tree Volcanoes
A couple of inches (2"), at most, is all that is needed to keep the weeds down.  Anymore and you can start to hurt the plants you are trying to protect.  The picture on the top right shows about six inches of mulch applied and it will kill the Azalea this year by rotting out the crown of the plant.  The 'Tree Volcanoes' at right show how after years of accumulating mulch, big mounds form around your trees and cause problems.  These trees, if you look closely, are dying.  The last two years large branches have fallen and they have been significantly pruned, and they continue to add piles of mulch.

Sometimes, mulch will smell bad like a science experiment went wrong.  This is often the result of poor practices in producing the mulch and it can damage your plants very quickly.  This is called sour mulch.

It is also important to get your shrub and perennial fertilizer down before the mulch is applied so it will be immediately useful for the plants and not absorbed by the mulch.

Adding mulch can be an aesthetic improvement to your gardens, but really, mulching should be considered your annual opportunity to improve the quality of the soil in your garden beds.  Adding some compost around plants under your mulch is another way to improve soil.  The Rhododendrons, Azaleas, Andromeda that are such a big part of our New England Gardens are very shallow-rooted plants and will respond quickly to good organic mater and good mulch.  The most important fact to remember is not to raise the grade around the base of your plants.

I hope you have learned some good information that you can put into practice.

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