The Virtues of Organic Mulch

By Andrea Laine

I used to look upon mulch as “icing on the cake” in my landscaped beds; a finishing touch that added visual benefit, but not much else. Boy, was I wrong! Mulch, especially the organic variety, is so valuable to vegetable gardens and flower gardens. Once I understood the wondrous things a mulch could do, I found it well worth the investment of time, energy and dollar to apply mulch every one or two years.

Herbaceous Border


Here are five benefits of using an organic mulch in your garden:

  1. Helps soil retain water – Mulch slows evaporation of water from precipitation or irrigation, which will help your plants weather hot, dry periods.  
  2. Reduces weeds  – A thick layer of mulch (two to four inches, no more) will prevent sunlight from reaching weed seedlings and block their growth. Weeds hardy enough to poke through mulch will be easy to spot and pull by hand.
  3. Insulates soil –  Mulch keeps soil cooler in summer–by as much as 10 degrees–and warmer during cool nights. During winter, mulch prevents the soil from freezing and thawing quickly minimizing damage to plant roots.
  4. Improves soil quality – As organic mulch decomposes, it enriches the soil below. Mulch also encourages earthworms to proliferate. Worms create spaces for air and water in soil and add nutrients to the soil via their castings.
  5. Protects soil from erosion and plants from disease – Mulch prevents plants and produce from coming in direct contact with soil. That helps protect the plant from soil-borne diseases and wet spots that may invite rot.  

When, What & How Much?

Mulch is best applied in the spring and/or in the late fall, after the ground has frozen. Various grades of pine bark or hardwood make good springtime mulches. Straw, shredded leaves, or pine needles make good fall mulch. Evergreen boughs are also useful as an overwinter mulch.
A coarser mulch, such as wood chips or nuggets, will last longer. You may be able to get away with replacing it every other year. Keep an eye on it, though; over time it can become compacted and begin to shed water. Gently cultivating it will solve the problem. A finer mulch, such as pine bark fines or triple-shredded hardwood, will break down faster thus improving the soil faster. It can do almost as much good as applying a layer of compost. The choice is yours to make depending upon the needs of your garden and personal preference.

Mulch For Gardening

Whatever type of mulch you choose, apply it in a two- to four-inch layer across your beds. Keep the mulch six to 12 inches away from tree trunks and plant stems. Without this breathing room, a plant may become too wet and invite disease or rot.  

You can purchase national brands of mulch at garden centers or buy it in bulk by the cubic yard* from a local distributor. These places typically sell sand, soil and compost in addition to mulches. Fresh wood chips are okay to use as mulch, so feel free to recycle a newly fallen tree from your land provided it is disease free.

Reap the Rewards

As you begin to prepare your spring gardening to-do list, consider working a mulch application into your plans. Your plants will be appreciative and reward you accordingly.

References & Resources

*Here is a step-by-step guide to calculating cubic feet/yards.

How to Mulch: Save Water, Feed the Soil, and Suppress Weeds by Stu Campbell and Jennifer Kujawski, Storey Publishing, North Adams, MA, Copyright 2015