To Mulch or not to Mulch

A major lawn herbicide was taken off the market eight to ten years ago because compost made with lawn clippings caused damage to plants the compost was applied around.  A specific herbicide sprayed on the lawns survived the heat and microbial process of composting.  A subsequent study found lawn clippings used as mulch after common lawn herbicides were applied damaged several vegetables.  Clippings from treated lawns caused damage for a few weeks after the herbicide application.  The bottom line is, “use caution” if you make pesticide applications to lawns then use the grass clippings for garden mulch.   

When planting beds, whether flower or vegetable, consider mulch for both aesthetics and weed control.  Below is a short discussion of different mulch or weed barriers.

Landscape fabrics – These are great for long term use in perennial plant beds or as removable weed mats in vegetable and ornamental gardens.  They are quite costly but last for years.  If in permanent landscape, bury under rocks or wood mulch and cut holes where plants will be planted.  Water and nutrients will filter through the mat but weeds won’t grow through the mat.  A few weeds may grow through the transplant hole and eventually enough dirt and weeds seeds will be present to grow a few weeds on top of the mat.  They are usually black on not very pretty.

Red plastic mulch

Plastic mulch – Plastic mulch works well in seasonal gardens, especially in vegetables.  They mainly keep weeds out but also can keep soils moist, and heat the soil for quicker growth in cold climates.  Water doesn’t penetrate plastic mulch so it must soak in from underneath the edges or have a water line under the plastic.  Clear, black, or colored plastic all work.  Weeds will grow under clear plastic but not colored or black plastic.  The aesthetic value is very low if using in ornamental beds.  Plastic is inexpensive.

Properly transplanting and mulching of a tree

Wood, Straw, Pine bark nuggets, Pine straw (needles) – These work similarly with the only variable being the texture and color.  Basically any vegetative material would work if it didn’t overload the soil with excess nutrients.  Most mulch is applied more for the aesthetics and then provides the weeds control.  In times past it was applied for weed control then when the mulches were visually appealing in the landscape the purpose shifted.  The problem with most mulch is it gets applied way to thick.  The worst is when it is mounded around tree trunks.  Many over mulched trees will eventually die. Organic mulch should be one to 2 inches thick and not cover the root flare on trees or lower the soil line on perennials and annuals.  These mulches have been shown to provide 80+ percent weed control when an inch thick.  A product of herbicide impregnated mulch now is on the consumer market for homeowner use.  It works and definitely should not be over applied. Tender transplants may not grow in around herbicide treated mulch. 
Grass clipping do work as mulch.  They have some nutritive value, but usually during the next year.  They can provide weed control just like any other mulch for weed control.  Some people have used odd materials such as cardboard.  Weeds rarely push through items like cardboard but it isn't very pretty.

Years ago a local scout troop I was associated with got the contract to supply mulch to several local church houses.  The troop was able to sufficiently fund its activities for two years with one day of several folks working hard.  A wood products company about a mile from my house has a major seasonal business of providing colored mulches bulk to homeowners who pick up one small pickup load for $30.  His mulch comes in two or three shades of red to brown, black, blue and who knows.  Blue wasn’t the most popular color but eventually disappeared.

The mulch business is big business.



Avoid volcano mulching trees