With the summer heat already here and severely limited water supplies, many of us are anxious to be able to keep our gardens beautiful during the long dry months ahead. Mulch can be a very good tool in this endeavor. But what is mulch and how do you use it?
Mulch is an organic material spread on the soil that can have many very useful functions for gardens and plants if you use the right materials. It cools and protects the soil from the drying and heating effects of the sun and helps retain soil moisture.
Mulch made from green waste and composted manure can increase soil organic matter levels over time, so the soil can hold more moisture and plants can withstand drought better. The right mulches can give all the fertility plants need, eliminating the need for fertilization. If you apply it thick enough, the mulch can suppress weeds. Mulch also dresses the gardens and highlights the foliage of the plants. Mulch makes our gardens much easier to maintain.
Chocolate cake consistency
Many materials are used as mulch. The best mulches for building healthy soil are organic materials that have been composted.
Composted green waste offered by local businesses or municipalities is often a good choice. Look for green waste that is mostly, but not entirely, decomposed, so there are coarser pieces as well as a compost-like component. Avoid green waste that contains large pieces of wood chips or bark.
Green waste with manure as an ingredient is exceptionally good. Composted manure is excellent as a mulch but difficult to find.
Many people use wood chips as mulch. These are not ideal unless used under mature trees like native oaks. Soil organisms very gradually break down wood chips. This long process uses a lot of nitrogen, depriving plants of essential nutrients. In fire-sensitive areas, wood chips around homes can also be a poor choice as they are flammable. Composted green waste has a texture similar to that of the soil and is not flammable.
Mulches contain varying amounts of nutrients. If you have drought tolerant plants and native plants, the composted green waste will likely contain enough nutrients. If you have more water-loving perennials or shrubs, you may want to look for composted green waste that contains manure or a fertilizer like feather meal (chopped chicken feathers). Bark mulch looks great but does not break down for many years and contains very few nutrients.
The organic matter in good mulch nourishes soil organisms that help develop healthy soil with good structure and porosity so that water seeps in and is retained. The goal is for the soil to have a chocolate cake-like structure that allows water and oxygen to pass through it as well as earthworms and other vital soil organisms. Water also adheres to humus and greatly helps develop the soil’s water-holding capacity.
A dressier look
Spread mulch on flower beds about 2 to 4 inches deep, depending on the size and age of your plants. The bigger and older the plants, the deeper the mulch can be. Small and young plants may only need a few inches of mulch initially. You can add more later, if needed. You want to keep the mulch from touching the stems and foliage of the plants. Applied a few inches thick, mulch helps cool the soil and protects against water loss. Plastic landscaping fabric, on the other hand, acts as a physical barrier for soil organisms and prevents nutrients from being recycled and soil organic matter from increasing.
Mulch is best used with drip irrigation. The mulch surface is often dry, so when you water from above with a hose, it can be difficult to get wet.
Bare soil invites weeds. Windblown seed weeds like dandelion, sky tree, poplars, and wild lettuce, germinate easily on bare soil. Most weeds produce large amounts of seeds and it can be difficult to weed plants on bare soil. Mulching the soil creates good structure and friability of the soil and makes weeding much easier. The plants are easy to pull up. Over time, pernicious perennial weeds like bindweed lose strength and vigor as soil structure improves. Just be sure to pull the plants out before they produce seeds.
In terms of appearance, mulch, like a crisp tuxedo, really dresses gardens. The brown color brings out the foliage and flowers.
The ideal time to apply mulch is in early spring, before the plants have grown much. But you can mulch now when the plants are tall, although it is a bit more difficult. You may need an assistant to maintain the foliage of the plant so that you can spread compost on the soil around the plant. Or you can just spread mulch over any bare soil. Again, don’t let it touch the foliage or stems. You can also apply mulch in the fall after you cut your plants for the winter.
With the water-saving and healthy soil benefits of mulch, try making mulching an annual practice.
Kate Frey’s column appears every two weeks in Sonoma Home. Contact Kate at: [email protected], Instagram @americangardenschool