There are many jobs required to keep a garden in good shape; weeding, composting, mulching, pruning, dead-heading (depending upon plant), watering, pest control and use of IPM principles, lawn care, edging, tool maintenance, chasing squirrels, and on and on. Of course, my favorite job – choosing the plants!
But in my experience, applying mulch is most important and beneficial of all garden chores. In addition to the most obvious benefit – aesthetics – mulch keeps roots cool in summer and protected from freeze/thaw in winter, conserves moisture that sandy soil loses so quickly, alleviates compaction and keeps soil friable by improving its structure, slows or stops erosion of top soil, counteracts the effects of poor soil texture, and makes weeding much easier. (Contrary to popular belief, weed seeds will germinate in mulch but the openness of the soil structure allows the plant and root to be pulled out intact. The exception, of course, is the dandelion.) But, the greatest benefit derived from mulching a garden is that it feeds the soil. It is said that one teaspoon of healthy soil contains millions of micro-organisms, and it is those micro-organisms that support plant growth and can make or break a garden. For soils such as we have in much of the PNW – sandy, lean, acidic, with little water-holding capacity – mulch is essential for improving pore space for water retention which in turn makes nutrients more available to plant roots. Mulch is crucial in xeric gardening, or in the gardens of those who put off watering in the summer months as long as possible (I water ornamentals only once or twice during summer months.) Mulch will break up the tight structure of soils comprised of heavy clay, giving roots ease of movement, greater access to water, and improved availability of essential nutrients.
In nutrient-poor soil, mulch supplies needed nutrients as it breaks down. Greater pore space facilitates the exchange of gases that roots require to maintain healthy growth. Better soil structure allows a greater number and variety of plants to be grown in the same bed, as is often the case in perennial beds. And last, mulch provides habitat for insects and the countless small creatures that help build soil.
Mulching twice a year (late fall and early spring) is a good habit to develop, but if time doesn’t allow then a deep layer of mulch once each year can do wonders for the garden. Keep fallen plant debris on the soil surface, also, unless it is diseased. Fallen leaves, twigs, cones, etc. are a good addition to mulch. If it looks messy to you, cover it with a light layer of mulch (or lower your standards). I’ve found this to be a very successful practice which keeps the garden looking tended and cared for.
One note of caution: while mulch is most effective when applied in a 3 – 4 inch layer in beds, keep it light around the root zone of plants (no deeper than 1 inch). Mulch applied too deeply around a plant’s root zone can prevent needed air from reaching the roots. And make sure not to touch the crown of the plant with mulch – this can cause rot.
Autumn is an important time of year to apply mulch – a surplus of fallen leaves and other plant material available and free to the first taker is a gift of health and beauty for your soil, and a gift to be treasured. Give your soil a little TLC and you will be richly rewarded.