All About Mulches.

3/7/2011

Mulches,

Organic and Synthetic

The aim of this article is to clarify the meaning of the term “Mulches.” In our gardens, Mulch is a covering of the ground around single plants or an entire row of plants. Mulches, are either Organic in composition (plant material), or Synthetic, i.e., made of plastics (a.k.a. film) or consisting of fabric material. Both serve multiple purposes as, a weed inhibitor, a moisture retainer, microbe enhancer/inhibitor, and protect the prepared ground from ‘soil compaction’ due to rain. Certain organic mulches also serve as slow feeding fertilizer.

In a process call ‘over-wintering’, mulch is used to cover the entire plants, usually tubers or rootstock as a protection form the harsh winter conditions. Organic mulches are the common choice used for over-wintering, however, materials such as old floor carpet is often used. When using carpet for this purpose, it needs removed at the first signs of spring, so not to smother the fresh young growth sprouting from the tubers or rootstock.

Organic Mulches

Organic mulch consists of any plant material that is chipped, shredded, ground, or otherwise processed into small mass. Common organic materials used are grass clippings, shrub trimmings, wood chips, Straw, Peat Moss, and newspaper, whole leaf or shredded. Included also, is incomplete compost, i.e., compost that has not reached its final stage and contains a large percentage of ‘rough matter’.

Caution: fresh green organic plant material if piled or thickly layered, produces allot of heat. The high heat can kill young plants and seed starts. This is the case with grass clippings; spread out the clippings to dry for a couple days before applying to young plants or seed starts.

The resounding benefits of using organic mulches are, it breathes allowing airflow to and from the ground, it is water permeable while at the same time retaining moisture, and is self composting which applies nutrients the root systems of the plants.

The disadvantage is that it needs reapplied several times in the growing season due to its gradual decomposition. A good practice is to apply the organic mulch, and then cap it with a layer of Peat Moss or Straw. This allows the initial application of organic material to decompose while the Peat Moss or Straw, which is slow to decompose, continues providing moisture retention and weed control throughout the growing season.

Many gardeners opt to use Straw instead of Peat Moss as a cap over organic mulch. Compost may be added directly over the straw at the end of the growing season, in preparation for next years crops. With Peat Moss, its best to rake into a pile, cover and save for the following season. Peat Moss will lower the soil Ph value (more acidity) when incorporated into the soil over several seasons.

Synthetic Mulches

Synthetic Mulches consist of agricultural plastics (a.k.a. film), and fabrics. Usually sold in rolls 4ft. wide by 20ft., 50ft., 100ft., or longer, and come in various colors. The most commonly used film and fabric color is black. However, the reflective color of the film mulch can greatly affect different species groups by increasing plant yield and/or repel disease-bearing insects. This effect is due to the reflecting of a specific bandwidth of color back up into the plant. In research conducted by the USDA and universities such as Clemons University, University of New Hampshire, amongst others, has concluded some very interesting results concerning the use of certain reflective colors of film mulches. Like all mulches, these reflective color film mulches suppress weeds and retain moisture. Below are listed some of the research results as to color.

Red film mulch: Reflective Red increases yields by 12-20% of Tomatoes and Strawberries.

Green film mulch: Reflective Green, increases earlier and heavier yields by 20-40%, of cucumbers, squash, melons (all types), and pumpkins. Also, works with peppers.

Silver film mulch: Reflective Silver is in a class of it own. Reflective Silver mulch is renowned for its ability to repel harmful disease-bearing insects. It is effective on insects such as Aphids, Thrips, White Flies, and Flea Beatles. Reflective Silver mulch is as effective, as regular pesticide applications for protecting tomatoes form ‘Spotted Wilt Virus’. This makes it especially attractive for use in Organic Gardens. Many large vegetable farms use Reflective Silver Mulch on all their Brassica crops.

Brown film mulch: Brown is more efficient for warming soil then Black mulch and suppresses weeds better then Reflective Green mulch. Brown mulch is a great all purpose film mulch, and Cucumbers, Squash, Melons, and Egg Plant all benefit from its use.

One disadvantage of using film mulches, that it is best to use drip irrigation underneath the film. Drip irrigation systems can be costly and are not always practical for the common gardener. However, with a little ingenuity and the use of recycled or repurposed materials, even the nonprofessional gardener can build a drip irrigation system for little or no cost.

The other type of synthetic mulch is Landscape Fabrics. They offer the benefit of being ‘water permeable’ as well as a great weed suppresser. Landscape Fabric is usually more cost effective then film mulch. A ‘new’ product is now available, it’s a fabric ground cover made from recycled plastic bottles, and it is ‘water permeable’ and a very good weed suppresser. 

Mulches, Organic or Synthetic serve common functions, and are their use in the garden is highly recommended. The conveniences of less watering and weed control are alone worth the effort. It is evident that mulches contribute to increased harvest yields and the overall health and vigor of our gardens.