Column: The Wheelbarrow Gardener – There is much to consider about garden mulch

As a gardener there are many things to consider about the garden when designing, building or maintaining one. Types and quantity of plants, colours of flowers, heights of trees, garden decor such as lighting, bird baths etc, but few give consideration to what type of mulch if any they are going to use in the garden. 

Mulch comes in so many different forms, the choices are endless. Organic options are things such as bark / wood chips, straw, pine cones / needles, grass clippings, paper and cardboard. Inorganic options are plastic, landscape fabric, gravel / decorative rock and chipped rubber. 
So many think of mulch as a purely decorative element, but there are several important functions of mulch. Let’s consider the function of mulch, why do we want it and what do we need it to do?

The main function of mulch is as a barrier between the soil and the environmental conditions.

Mulch is great at preventing evaporation of moisture from the soil which conserves water preventing the need for frequent watering. It can also help prevent fluctuations in soil temperature, keeping soil warmer during cool periods and, keeping it cooler during hot spells, all of which benefit the plant’s roots. 

Mulch is also a barrier for sunlight which helps control the growth of weeds as they don’t get the required amount of sunlight to germinate. Keep in mind if it stops the weed seeds it stops the other good seeds (such as those from perennials that self seed to propogate) from growing as well.  Weeds that do manage to grow in the mulch are easily removed.

Mulch makes good walkways, especially in vegetable gardens. Layers of newspaper, grass clippings, or straw all help suppress the weeds but also help keep your feet clean when in the garden weeding or harvesting. These mulches will also slowly decompose and feed your garden as well. 

The use of organic options provides a much needed slow release of nutrients to your garden as it decomposes. 

Despite the many benefits of mulch, there are also some drawbacks. Especially when it comes to the inorganic variety. Plastic or landscape fabric with a layer of rock or chipped rubber on top can compact the ground preventing water and oxygen from getting to the roots of nearby plants. For that reason never use the plastic/rock combo in areas where plants are growing, and because plastic does not let water pass through it can cause flooding problems if some sort of drainage system is not built into the design.  Plastics and landscape fabrics do not breakdown, therefore they are not an environmentally friendly option and in comparison are more expensive than the organic counterparts which in some cases can be free. 

Some things to consider when choosing and placing a mulch: 

1/ Is this a temporary or permanent placement? If it’s temporary, an organic option may be a better choice. Less expensive and easier to change in the future, unless you enjoy moving yards of gravel or river rock. It is a great workout.

2/ How deep does it need to be? If you are putting a barrier underneath such as cardboard, plastic or landscape fabric you will need less, just enough to cover the ground evenly. If you are going barrier free then you will need more as you will want to make sure no sun or seeds can get through. Always speak to your mulch supplier for recommended depths. They will also help you figure out exactly how much you need to cover a certain area. 

3/ Keep in mind just because it is a bark mulch it may not be a great organic choice as coloured mulches are treated with chemical dyes. Stick with the natural mulches, it’s a much better option.
4/ Never put any mulch directly against the base of perennials, shrubs or trees. Keep the mulch at least 4-5 inches away from the base of perennials and 6-12 inches away from the trunk of trees and shrubs. During winter months, rodents can make homes in the mulch and if they can take up residence right next to a tree trunk they will have a constant source of food all winter long.  Keeping the mulch away will also aid in the quick delivery of nutrients such as fertilizers to the soil. 

5/ Using a cedar mulch can control certain pests as the cedar has a natural oil that acts as an insect repellant.

Mulch can add a beautiful element to any yard but visiting a landscape supplier can be a bit intimidating. With the many choices available you might want to have someone like myself come with you. We can provide suggestions, make recommendations and help liaison between you and the supplier. This will be a investment of time and money, make sure it’s done right.

Valerie Loseth, The Wheelbarrow Gardener

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