Fall Mulching

After removing annual plants and veggies—and cutting back herbaceous perennials—add a 1-3” layer of finished compost or manure directly on top of the ground. If there are evergreen perennials, shrubs, or trees—avoid covering the root zone or mulching against the trunk. Remember, there’s no need to dig! The compost will work its way into the soil throughout the winter while helping to create a nice loamy texture. It will also add important micronutrients, beneficial fungi, and bacteria into the soil food web.

It’s also a good idea to add greensand, rock phosphate, bone meal, or any dry organic amendments at this time. They will slowly break down and provide nutrients just in time for spring planting. Fall is also the perfect time to add lime to vegetable beds and lawns. Our soils tend to be a bit acidic, and a yearly dose of lime helps raise the pH.

Mulching with bark, straw, leaves, or other materials can also be done in the fall. Mulch can help insulate tender plants. Covering the soil also helps reduce compaction due to rainfall while helping to keep weeds at bay. Please note, plant-based mulches hold in moisture, so it’s important to avoid covering plants that need good drainage with these sorts of materials. You can mulch around drainage-sensitive plants with pumice or gravel instead. If there is still a thick layer of leaves or other mulches that haven’t decomposed by springtime, simply rake up the material. The soil will warm up faster in the spring if it is bare.

When cleaning up dead plants or fallen leaves, remember to remove and discard any plants that had mildew, black spot, insect infestations, or other pests and diseases. These problems can live in the soil from year to year if infected parts are left trot on the ground or in the home compost pile.

When applied correctly, mulch has the following beneficial effects on plants and soil:

• Mulches prevent the loss of water from soil by evaporation.
• Mulches reduce the growth of weeds—but only when the mulch material itself is weed‐free and applied deeply enough to prevent weed germination while smothering existing weeds.
• Mulches keep the soil cooler in the summer and warmer in the winter, thus maintaining a more even soil temperature.
• Mulches prevent soil splashing, which reduces erosion while keeping soil‐borne diseases from splashing up on plants.
• Organic mulches can improve the soil structure. As the mulch decays, the material becomes topsoil.
• Decaying mulch also adds nutrients to the soil and promotes the health of microscopic flora and fauna within it.
• Mulches prevent crusting of the soil surface, thus improving the absorption and movement of water in the soil.
• Mulches prevent the trunks of trees and shrubs from damage by lawn equipment.
• Mulches help prevent soil compaction.
• Mulches can add to the beauty of the landscape by providing a cover of uniform color and interesting texture to the surface.
• Mulched plants have more roots than plants that are not mulched, as mulched plants will produce additional roots in the mulch that surrounds them.

There are basically two types of mulches: organic and inorganic. Both types may have their place in the garden.

An organic mulch is a mulch made of natural substances such as bark, wood chips, leaves, pine needles, or grass clippings. Organic mulches attract insects, slugs, worms and the birds that eat them. They decompose over time, adding nutrients to the soil. They need to be replaced every few years.

Inorganic mulches—such as gravel, pebbles, plastic and landscape fabrics—do not decompose. While they are longer lasting, they add nothing to the soil.

Organic Mulches
Your yard debris can be recycled as mulch with the advantage of retaining the nutrients found in these organic materials. Additionally, you will save money and reduce your environmental impact by not transporting and disposing of it.

Grass Clippings
The best use for grass clippings is to leave them on the lawn. Grass clippings will decompose rapidly, adding nutrients back into the soil. If it’s not full of weed seeds, a two‐inch layer of grass clippings provides weed control. It is best to build up the layer gradually using dry grass, not fresh clippings, to prevent the formation of a solid mat. Be careful not to use clippings from lawns that have been treated with herbicides.

Hay and Straw
Hay contains too many weed seeds and should never be used as mulch. Straw decomposes rapidly, so you will have to replenish it to keep the weeds down. Straw is not very ornamental and is best for a vegetable garden or over newly sown lawns. Straw will improve the soil as it decays.

Leaves
A 2 to 3 inch layer of leaves provides good weed control. It is best to shred the leaves coarsely, using a shredder or your lawn mower. Whole leaves have a tendency to blow away, while finely shredded leaves do not allow water to penetrate. Oak and beech leaves help to acidify the soil for acid‐loving plants. Leaves are usually easy to get, attractive as a mulch, and they will improve the soil once they decompose. After the leaves decompose, dig them into the soil and add a new layer of mulch on top.

Fir or Hemlock Bark
A 2 to 3 inch layer of softwood bark is good for weed control. Softwood bark makes an attractive, medium to dark‐colored mulch. It can be purchased in various particle sizes, from shredded to large‐sized chunks called nuggets. Large bark nuggets float in water and may not stay in place during a heavy rain, especially on slopes.

Wood Chips
This material contains bark and pieces of wood of various sizes and makes an attractive mulch. A 2‐3 inch layer of wood chips provides good weed control. Small wood chips decompose very rapidly, drawing nitrogen from the soil which will need to be replaced by nitrogen fertilizer.

Ground Cover
Many perennial ground cover plants—such as thyme, pachysandra, mondo grass and liriope—will cover the soil and act as a mulch.

Gravel, Pebbles, or Crushed Stone
These materials are permanent and are best used for permanent plantings such as foundation plants. A 1 inch layer of small rocks will provide good weed control. Do not use them around acid‐loving plants, as the rocks may add alkaline elements and minerals to the soil. These materials reflect solar radiation and can create a very hot landscape environment during the summer months.

Black Plastic
Black polyethylene film is very effective in preventing weed growth. That said, it also holds water in the soil and is not recommended for poorly‐drained areas. Doing so may cause the soil to remain too wet, resulting in root disease problems. You may have to cut holes in the plastic if water does not go through it, although there is black plastic available that has small holes in it to help with drainage. If exposed to sunlight, black plastic breaks down quickly, losing its effectiveness as a mulch. However, if you bury black plastic in the soil, it will last for many years. Covering the black plastic with a layer of wood chips or pine needles will reduce heat absorption and mask its artificial appearance.

Clear Plastic
Clear plastic will not suppress weed growth because light penetrates the film and raises the soil temperature, which may result in an increased growth of weeds in early spring.

Landscape Cloth or Woven Ground Cloth
Materials woven of fabric, plastic, or paper are available in various lengths and widths. The materials are treated to resist decomposition. Unlike plastic films, woven materials allow water and air to move through them. They are very effective in controlling most weeds, although some grasses may grow up through the holes in the fabric. Landscape cloth needs to be fastened down so it will not be pushed up by perennial weeds. Better moisture, temperature, and weed control will be obtained by adding several inches of another mulching material on top of the landscape cloth.

Ground Rubber Tires
Mulches made of ground rubber tires do not decompose and will therefore never need to be replaced. However, the use of ground rubber tires is relatively new and its effectiveness as a mulch is still being evaluated. Be aware that rubber contains many hazardous chemicals which may leach into your soil over time.

Tumbled Glass
Tumbled glass is extremely durable and comes in a wide range of colors, but is also expensive and not widely available. Because of the cost, it is best used in small areas such as containers.

Mulching is very important for establishing new plantings. It helps to conserve moisture in the root ball of the new plant until the roots have grown out into the surrounding soil. The growth rate and health of trees and shrubs increases when there is no competition for water and nutrients from weeds. Mulch also helps to prevent tree trunk injury by mowers and trimmers. Newly planted trees require a circle of mulch 3-4 feet in diameter.

Maintain this for five years. Mulch entire beds of shrubs, trees, annuals, herbaceous perennials and ground covers.

Mulch can also be used to cover trails, driveways, play areas, and natural areas.

Light‐weight mulch—such as dried grass clippings and pine straw—can be used temporarily to cover low‐growing tender plants and protect them from frost injury.

The best time to mulch new plantings is right after you plant them. For established plants, mulch is best applied in early spring. This is when plants are beginning to grow and before weed seeds start to germinate.

How often mulch needs to be replenished depends on the mulching material. Grass clippings and leaves decompose very quickly and need to be replenished frequently. Inorganic mulches, such as gravel and pebbles, rarely need replenishing. As the plants grow and fill in the bed areas, less and less mulch is needed.

Before applying any type of mulch to an area, it is best to weed the area thoroughly. Next, spread a layer of mulching materials over the entire plant bed. Keep mulch 2-3 inches away from the stems of woody plants. This will prevent decay caused by wet mulch and rodent damage during the winter.

Keep mulch 6-12 inches away from the walls of buildings. Subterranean termites nest in the soil and feed on materials that contain cellulose. Termite treatments are applied to the soil around buildings, so keeping mulch away from walls will prevent termites from using it as a bridge to cross treated soil.

Newly planted trees require a circle of mulch 3 -4 feet in diameter. Maintain this for at least three years. Do not pile mulch against the trunk. For established trees in lawns, create a circle of mulch about 2 feet in diameter for each inch of trunk diameter. Increase the size of the mulched area as the tree grows. Try to apply the mulch at least 6-12 inches beyond the drip‐line of the tree. Because the root system can extend two to three times the crown spread of the tree, mulch as large an area as possible.

Proper mulch depth depends on the texture and density of the mulch material. Many wood and bark mulches are composed of fine particles and should not be more than 2-3 inches deep. Excessive amounts of these fine‐textured mulches can suffocate plant roots, resulting in yellowing of the leaves and poor growth. Coarse‐textured mulches, such as fir bark nuggets, allow good air movement through them and can be as deep as 4 inches.

Mulches composed of grass clippings or shredded leaves should never be deeper than 2 inches. These materials tend to mat together, restricting the water and air supply to plant roots.

To determine how many cubic feet of mulch is needed, calculate the surface area and the desired depth of coverage. There are 27 cubic feet in a cubic yard. One cubic yard will cover a 324‐square‐foot area with an inch of mulch.

Figure out the square footage of your bed. For square or rectangular shaped beds, multiply the length of the bed by the width of the bed. The square footage of a circular bed is the distance from the middle of the circle to the outside, multiplied by itself and then multiplied by 3.14 (which is pi).

Multiply your square footage by the depth desired (in inches) and divide by 324 square feet. This will tell you how many cubic yards you will need. Feel free to ask us for assistance with mulch questions, selection, and calculations. We are always happy to help!