Organic mulches, such as aged hardwood bark mulch, is a wonderful thing.

It moderates soil temperatures, preserves soil moisture, suppresses weeds and as the mulch slowly decays, it contributes to the organic content of the underlying soil. If used properly, mulches enhance landscape aesthetics.

How do I know what organic mulch is best for my landscape? There are so many choices. Organic mulch is derived from once living plant-based products. When selecting a mulch, consider not only cost and color, but also where it came from.

Durability is another important consideration. Organic mulches decompose over time. As they do, they settle, reducing the depth of your mulch layer.

Common organic mulch choices include cypress, hardwood and recycled pallets. Cypress mulch is harvested from the cypress trees in the swamp areas of the South. One of the reasons these trees can grow in flooded conditions is their wood repels water.

Cypress mulch is ideal for use around walkways and driveways, and not flower or vegetable gardens, because of the tendency to repel water away from landscape plants.

Recycled ground pallets mulches are often dyed to add red, brown, black, or gray color to your landscape. The University of Massachusetts Extension gives information on the dyes used. The dyes used in coloring wood mulch are primarily of two types: carbon-based dyes and iron oxide-based dyes. Iron oxide, the most used dye, is simply a compound of iron and oxygen.

As the compound oxidizes, iron is released to the soil. Iron oxide dyes are often used in the floriculture industry to dye flowers. The other type is the carbon-based dyes. These carbon-based colorants are like those used in ink and cosmetics. Dyes that are not absorbed into the wood correctly may come off with contact, especially if the mulch is wet such as after a rain event, staining sidewalks, and other areas. At this time, there is no evidence that the dyes used to color pallet mulch is toxic.

Hardwood mulch is comprised of many different hardwood and softwood species. In general, hardwood mulches have a high carbon to nitrogen ratio. This means that in the process of decomposing, they may temporarily reduce the supply of soil nitrogen fertilizer to mulched plants.

Compared with other mulches , hardwood mulches tend to lose more of their decorative appearance over time, weathering to a gray or silvery gray color.

The proper application of mulch around trees and landscape plants starts with producing mulch rings or areas as large as is practical. Keep in mind that organic mulch is an effective stand-in for leaf litter found naturally under trees and shrubs. It is also a great way to reduce direct competition between turf and tree roots.

However, the mulch should be applied to a depth of no more than 2-3 inches. Mulch that finds its way onto the tree trunks should be pulled away from the trunk flare. The trunk flare is the area where the tree trunk and the roots are forming . The trunk will have a flared-out appearance.

Avoid piling mulch high around trees and shrubs, a practice that has been coined Volcano mulching. Excessive mulch more than 2-3 inches around trees and other landscape plants cause bark damage.

The excessive mulch retains water that causes the living tissue of the bark of your plants to decay. This allows insects and other plant pathogens to cause further damage. Of course, the pests and diseases get blamed if a tree or shrub declines and dies, and not the mulch that was applied to heavily in the first place.