Monday, April 1, 2013

Mulch–Choices that Affect the Soil

Mulch is a covering put on gardens and landscape that can benefit the soil. Mulch can be organic material.  Mulch can be inorganic material.  mulch can make a garden look finished.
   Mulch can also make gardening easier.  Mulch can save water.  Mulch can smother grasses and weeds in the garden.  Mulch can keep weed seed from germinating. Mulch can keep soil temperatures stable.  Mulch can reduce and prevent erosion.  Mulch can add organic material to the soil.  Mulch can keep soil borne diseases from splashing onto foliage.

This graphic is one of my favorites when mulch is being discussed.  The benefits of mulch being applied to the garden are many.  The materials that are used as mulch also are many.  Let’s take a look at some of the good choices for mulch 

Wood chips,and  wood bark are probably the most used mulches used in landscaping.  The wood make the landscape looked well groomed, and has all of the benefits of any mulch choices.  The size of the wood chips can be fine grind or course grind.  The larger nuggets tend to move around in the garden, especially if there are hard downpours of rain.  Smaller chips will decompose faster than larger pieces, and will need to be replaced more often.
One of my favorite mulches is pine needles.  Many of our gardening friends in the South US have unlimited supplies of pine needles.  But those of us in the North have to buy bales of pine needless to spread in our gardens.  Pine needles are ‘slightly’ acidic and are slow to decompose.
The acidic nature of pine needles benefits plants that need a low pH to grow.  pH below 7 is considered acidic, and azaleas, rhododendron, and holly need acid soil to thrive.  In fact, most plants, including food crops like a pH in the 6 – 7 range on the pH scale as slightly acidic.
Other mulch choices include straw, grass clippings, and cocoa shells.  I really like cocoa shell mulch.  It is dark, decomposes slowly, and – guess what! – it smells wonderful.
cocoa mulch


When using grass clippings to mulch, especially food crops gardens, be sure they are herbicide-free to reduce contamination of the food you are growing.
For many years I have used newspapers as mulch.  This helped reduce landfill contributions of tons of paper. When 5-6 layers are put on grass or weeds, it is a successful in smothering them and makes the area ready to plant in about 8 weeks.  Heavy cardboard works the same way.
Inks of most publications are soy based and will not harm the soil.  However, colored magazine or ads from the newspaper should be avoided, as these inks may contain harmful pigments.
Old tires are being recycled into mulches.  In theory this is a good way to keep tires out of landfills.  However, the rubber contains zinc and leaches into the soil.  I would hesitate using rubber mulches on food crops. 
Another source of mulch is recycled wood from pallets.  Many facilities are grinding this wood into shredded mulch, and offering it to the consumer in multiple colors.
The dyes used in this process are vegetable based and will bio-degrade safely into the soil.  However, some sources I have seen are cautioning  that this wood source maybe contaminated.  Shippers have issues with insects and rodents in cargo, and some of these pallets are saturated with these insecticides and arsenic. 


One other mulch I will ask you to NOT use is cypress mulch.  The problem with cypress is that the gulf coast region is being harvested of these trees, and area eco-systems are being destroyed.  Even small basins and swamps are drying out.  The natural floodwater controls are being affected. More trees are harvested than can regrow so this source is unsustainable.  Wildlife refuge and habitats are disappearing.


Gravel and stones can be used as mulch.  They can smother weeds, and look pretty at the base of some plants.  Careful plant choices are required with this type of mulch, however, since rocks can hold a tremendous amount of heat and plants can ‘bake’.  The use of succulents and cactus may be suitable for this type of mulch.  Alpine plants and other rock garden choices will hold up as well.
pebblesrock mulch

Springtime is typically time to mulch the landscape.  The soil should be fairly warmed up since mulch, while regulating soil temperatures, may hinder the warm-up if put on too cool of soil.  Some food crops, like tomatoes need warmer soils.
Another faulty practice concerning mulching is ‘volcano’ mulch.  We have all see this time and time again, only to see this result. The bark of the tree holds moisture and trees are set up to fail from bacteria, fungus, and insects. Never put mulch right up against the trunk and never more that 3” – 4” deep.

volcano mulch
mulch for trees

Mulch is a key to healthy soil, healthy plants, and environmentally sound gardening practices.  Mulch inhibits weeds – reducing herbicides and hand digging.  Mulch saves water – soil dry out less frequently which requires less supplemental water. Mulch – organic mulch- will gradually decompose and add nutrients back into the soil. 


Spring is Finally breaking in my Zone 6 garden, and mulch is not far behind.  We have Mulch to Do!

What is your favorite mulch?  Let us know.  I love to hear from my readers.  Have a great Spring.
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