It is almost an annual spring ritual for many gardeners to add mulch to their garden. Using the word ‘mulch’ can mean a variety of different materials, but here in the Pacific Northwest, it usually refers to bark dust or compost and is often a blend of the two. In some areas where there are mushroom growing facilities, the material left over after the harvest is sold as mushroom compost and it is usually mixed with bark dust. Mulches also include peat moss, shredded and un-shredded leaves, hay, straw, paper, lawn clippings, gravel and other material that is spread on the ground and around plants.
There can be many reasons for using a mulch, one of which is simply visual. A garden with a new layer of black mulch is perceived as visually very appealing. In my own garden, we add a layer of garden compost each spring and the ‘before’ and ‘after’ look is amazing.
In addition to the visual aspect, a mulch has many benefits to both the soil and the plants growing in it. A mulch provides weed suppression and it also makes those weed seeds that do germinate easier to pull. A garden compost mulch should have generated enough heat in the compost making process to kill most weed seeds. Of course, there will be weed seeds in the existing soil, but with a layer of garden compost, they are much easier to remove. With a yearly addition of mulch, I have found that each year weeds become less and less of an issue.
Another benefit of adding a layer of garden compost is the benefit it provides to plants. The mulch will help to retain moisture which can be especially beneficial for those plants like hydrangeas and many ferns that prefer a moist soil environment. In addition, a garden compost mulch helps retain soil moisture and can also help the soil structure as well as provide some nutritional benefits. Compost has nitrogen, phosphorus, and potassium and it also provides some nutrients that plants need in small amounts. Garden compost is available in bags and Wilco has a good selection to choose from.
I have found that bags are useful in the summer when I need small amounts. During the past several years, I have found it is beneficial to add a top dressing around plants that are in pots, especially those that are located in a sunny location. Adding a mulch will help prevent the soil from drying out so quickly on some of our hot summer days. For larger quantities, many gardeners will order their mulch in bulk and have it delivered. When placing a bulk order, it is a good idea to know the square footage of the area to be mulched. To figure square footage, multiply the length times the width. A ‘unit’ is a term often used when ordering bulk mulches. One unit is equal to 7.4 cubic yards and if spreading the mulch one inch thick, a unit will cover about 2,400 square feet.
As mentioned earlier, there are other materials that can, and often are, used as mulch. Lawn grass clippings are often used in small areas. Be sure not to spread grass clippings too thick as they will form a mat that can actually inhibit water penetration. Also, be certain that a weed and feed product has not been used on the lawn as this could cause damage when the clippings are used around plants.
Sometimes even gravel can be beneficial when used as a mulch. Joy Creek Nursery in Scappoose uses ¼-10 crushed basalt as a top dressing for certain plants such as penstemon and some salvia. These plants need excellent drainage to survive our wet winters and the gravel helps wick the moisture away from the stems.
Just like we learn about our plants and their needs, we need to also learn about our soil and the needs that is has. I recommend having a soil test every couple of years to give you the information you need to determine if your soil needs the addition of the organic matter that a mulch provides. In my garden, a spring ritual is two units of garden compost.