Use Mulch

Boost your landscape with
smart mulching

Layers of organic litter. Deciduous forests are one of nature’s champion mulchers, shedding leaves in autumn that are transformed by the soil’s natural food web into plant food and the rich organic matter called humus that is the key to healthy woodland soil. This blanket of organic matter protects plant roots from extremes of temperature, limits soil erosion, and conserves soil moisture that could otherwise evaporate.

Mulching a garden:

• Conserves water by shading the soil and reducing evaporation
• Insulates roots by moderating soil temperatures
• Cushions the impact of downpours and helps prevent soil compaction, allowing water to penetrate and plant roots to breathe
• Adds nutrients and organic matter to the soil as it decomposes, improving water retention and nurturing the soil fauna that promote fertility
• Suppresses weeds, reducing the need for regular cultivation

Inorganic mulches, such as crushed stone, are appropriate for xeriscapes and rock gardens. In most cases, however, organic mulches are preferable for traditional planting beds because they eventually break down and enrich the soil.

Bagged and bulk mulches are commercially available, but you can save money and reduce your carbon footprint by mulching fallen leaves and other organic materials from your property.

How to apply mulch

• Mulches are not soil amendments, and need to be applied on the surface of the soil.  Do not mix mulch into the soil—then it’s not mulch anymore!
• Wood and gravel mulches should be about 4 inches deep to suppress weeds. At least 3 inches is recommended for preventing evaporation from the soil surface.
• Before applying mulch, pull any existing weeds or smother them with a layer of newspaper, then water well.
• To avoid certain diseases, keep organic mulch back like bark or wood chips back an inch or two from the base of plants.
• The best time to spread mulch around heat-loving vegetables like peppers and tomatoes is after the soil has warmed, usually mid or late spring. Cabbages, greens and other cool-weather crops can be mulched earlier. Mulch can be applied anytime in herbaceous perennial beds and around trees and shrubs.
• Don’t mulch seedlings planted in very moist soils because excessive wetness is an invitation for damping-off, an often fatal fungal disease. Once seedlings are established, it’s safe to mulch.
• Because organic mulches eventually break down and become part of the soil, they may need to be renewed every two or three years, depending on the climate and the type of mulch.

Some recommended organic mulches

• Leaves – Leaves make a great mulch, and they’re also free. Partially shredded leaves are less likely to mat and shed water than whole leaves, leaves can be run through a shredder or pass the lawn mower over them a few times to produce a finer mulch. Composting durable leaves that decompose slowly (like oak or cottonwood leaves) with grass clippings for a week or two will improve them as mulch.
• Bark – Because they’re often a recycled byproduct of the lumber industry, they can be a sustainable choice.
• Wood chips – Wood chips are also a byproduct of lumber and landscaping industries.  Local tree companies and municipalities may even make wood chips available for free.
• Pine needles – Pine needles are light and fluffy and don’t get compacted, so water penetrates easily. Like other organic mulches, avoid using them near structures in areas at risk for wildfire.  Contrary to popular belief, pine needle mulch does not acidify soil.
• Nutshells – If nutshells are an agricultural byproduct in the area, they are a good choice. If you’re a pet owner, beware of cocoa hulls, a byproduct of chocolate processing, which contain compounds toxic to dogs.
• Straw – Straw can be effective if short-lived mulch, but be sure you get straw and not hay, which can be full of weed seeds.
• Compost – Compost is not mulch. Top-dressing annual flower and vegetable planting beds each year with an inch of compost will provide most plants with a balanced source of nutrients but does not provide the same benefits as mulch – add a cozy blanket of mulch over your compost to reap maximum rewards.

Plant “green manure” cover crops

Growing “green manures” — grains and legumes used as cover crops — can be a good way to increase the amount of organic matter and nutrients in soil in annual or vegetable gardens. Cover crops reduce the need for fertilizer, help aerate the soil, increase its capacity to conserve moisture, and protect it from compaction and erosion during storms. They also help suppress weeds. Grains such as wheat and oats are especially good at increasing soil’s organic matter. Leguminous cover crops, like vetches, clovers or cow peas, contain nitrogen-fixing bacteria in their root nodules that remove nitrogen from the atmosphere and make it available in soil.

Growing tips:

• Use cover crops over bare vegetable beds in winter.
• For multiple benefits, grow grains and legumes together.
• To get them off to a good start, plant winter cover crops at least four  weeks before the expected first hard frost date in your area
• Plant cover crops with large seeds, like peas, in shallow, closely spaced furrows; broadcast those with small seeds, then rake lightly to cover.
• If the weather is dry, water to keep the soil lightly moist until the young cover crop is established
• DO NOT allow cover crops to go to seed
• Terminate and till in cover crops into the soil in spring, just before flowering, or about 3 weeks before planting to give the organic matter time to start breaking down.
• Avoid cover crops that are invasive in your region.