The Guide to Organic Mulches

Wood chips are available in various sizes, catering to different needs. Some smaller-sized wood chip mulches are often referred to as "ground" wood mulch. These wood chips are derived from the lumber industry and are typically dried and aged before being packaged in large bags. To suit various garden decors, they can also be dyed in colors like black, brown, or red.

When it comes to choosing the right mulch for flower beds and borders, hardwood chippings that have started to decompose are highly recommended. These chippings break down more quickly, contributing to soil improvement. Additionally, they blend naturally with garden landscapes, providing a pleasing aesthetic. On the other hand, softwood chippings, especially pine, decompose at a slower rate and can have a more acidic effect on the soil. Therefore, they are better suited for use around trees and large shrubs.

It's important to consider the size of the wood chips when selecting mulch. Smaller chips are more likely to stay in place, while larger chips are lighter and more prone to being blown around or washed away during heavy rainstorms.

Wood chip mulch is best for: 

• mulching trees and shrubs
• flower beds
• perennial flowers
• orchards
• walkways in flower and vegetable gardens

Depth: 2-4 inches, depends on the size of the chips or how finely ground it is. Bigger chips can be applied more deeply.

Advantages: 

• attractive
• adds organic matter
• allows water in
• prevents evaporation of water
• suppresses weeds well
• moderates soil temperature
• free of weed seeds
• smaller chips are less likely to blow or wash away than larger chips
• doesn’t readily compact
• reduces and/or reverses soil compaction
• inexpensive

Disadvantages: 

• Larger chips can blow or float away 
• It must be topped off — top-dress larger chips every 1-3 years, smaller chips every 1-2 years

Notes:

• Avoid mulch volcanoes when you mulch your trees
• Wood chip mulch isn’t recommended in vegetable beds next to plants but is fine to use in vegetable garden pathways
• In annual flower beds, rake off the mulch before planting and re-mulch after your plants are in to avoid turning it under and creating a possible nitrogen deficit

Grass clippings are best for:

•  Your lawn, if you have a mulching mower. Mulching your grass clippings can reduce your lawn fertilizer needs by up to 25%. 
• The next best place to use them is your compost pile. 
• You can use them in your vegetable garden if you’re careful about how you apply them.
• Ideally, use grass clippings in a flower bed and turn them into the soil at the end of the season. This will prevent a smelly build-up and will allow the nutrients of the mulch to blend into the soil and improve it. 

Depth: up to one inch.

Advantages: 

• allows water in
• prevents evaporation of water
• adds organic matter to soil
• typically free of weed seeds
• can be turned under at the end of the season
• they are free
• suppress weeds

Disadvantages: 

• can mat down into a stinky, slimy mess
• can blow away

Notes: 

• Allow the clippings to dry out first and apply them in thin layers. Add additional thin layers as they decompose
• Don’t use clippings in your garden if they were sprayed with weed killer, if the lawn has gone to seed, or has many weeds

Straw mulch is the best organic mulch for vegetable gardens and newly seeded lawns. It’s especially helpful for keeping your soil cool in the warmer months. When used in vegetable gardens, it provides a welcoming home for spiders and beneficial insects, which will help to keep pest problems under control. It also prevents soil-borne diseases from making contact with the lower leaves of vegetable plants.

Depth: 2-3 inches

Advantages: 

• allows water in
• prevents evaporation of water
• adds organic matter
• suppresses weeds well
• moderates soil temperature
• can be turned under at the end of the season
• a barrier when growing vegetables that would otherwise come in contact with the ground
• prevents lawn seeds from being washed away
• pretty inexpensive

Disadvantages: 

• can blow around easily
• may have weed seeds in it
• has to be replenished annually 
• flammable
• not super attractive

Notes:

• Purchase straw, not hay. Hay has lots of weed seeds in it 
• Pre-sprout weed seeds in your straw by watering the bales a couple of weeks before spreading the straw. Remove any that have sprouted as you spread it.

Composted food waste, garden products, and manure can be used to create an excellent soil mulch. Before applying it, make sure your compost has been broken down well and then spread it around the base of your plants. The compost will provide the soil with a slow-release nutrient boost and add a layer of insulation to protect plant roots from extreme temperatures, improving drought tolerance.

Besides, compost works great between other layers of mulch. To do this, apply a thin layer on top of the soil, and then cover it with a different mulch type such as bark or wood chippings.

Cover crops can improve your garden soil and reduce weeds. Ryegrass, winter rye, oats, buckwheat, barley, and annual clovers are examples of cover crops that you can grow.

Cover crops are best for:

• vegetable gardens
• orchards

Advantages: 

• improves soil structure
• add lots of organic matter
• prevent water from evaporating
• suppress weeds
• soil protection
• pest control
• allows water in
• moderate soil temperatures while they’re growing
• attract many beneficial insects when they flower
• providing habitat for pollinators
• harbors slugs and snails

Disadvantages: 

• won’t be able to grow vegetables while you’re growing a cover crop

Notes: 

• You must turn cover crops under or cut them down before they go to seed or they’ll spread and become a nuisance
• Depending on where you get your manure, you may find weeds and other sprouts pop up occassionally

Shredded leaves are another type of mulch you can get for free by collecting the fallen leaves from around your property and shredding them. Leaf mulch is high in nutrients and will help to improve the condition of your soil; it also provides a home for earthworms and other soil-improving creatures.

Leaf mulch is best for:

• vegetable or ornamental garden.

Depth: 2 inches

 Advantages: 

• allows water in
• prevents evaporation of water
• adds organic matter
• typically, free of weed seeds
• can be turned under at the end of the season
• leaves are free

Disadvantages: 

• can easily mat or blow away
• must collect them in the fall and have a place to store them over the winter if using them in the spring
• can look messy

Notes: 

• Mix shredded leaves with straw to prevent matting

If you have pine trees on your property, then you can rake up the fallen needles and spread them amongst plants as mulch. They make an attractive, natural-looking mulch, and are of course, completely free. 

Pine needles work best for: 

• ornamental plantings
• orchards
• vegetable garden

 Depth: 1.5 – 3 inches

 Advantages: 

• allows water in
• prevents evaporation of water
• moderates soil temperature
• suppresses weeds somewhat
• lasts a long time
• free of weed seeds
• provides good winter protection for fall transplants because it resists compaction

Disadvantages: 

• can’t be turned under at the end of the season
• fire hazard
• can look messy
• adds little organic matter
• doesn’t suppress weeds as well as other mulches like wood chips or straw

Notes:

• Pine needles don’t affect soil pH, contrary to popular belief
• You may only need to top off this mulch every few years
• If you have large, long-needled evergreens, you can harvest your own mulch.

Cocoa hulls fall in and out of favor among gardeners, as information regarding its safety fluctuates. They are widely regarded as poisonous to dogs and other wildlife, and though this claim sometimes gets refuted, it is best to steer clear of cocoa mulch if you have pets in the home. 

For some people, though, cocoa hulls are a popular choice of mulch, thanks to their warming brown color, and their rich, chocolatey scent. 

Cocoa hulls are best for:

•  vegetable gardens

Depth: 1-inch max

Advantages: 

• are attractive
• allows water in
• prevent evaporation of water
• add organic matter
• suppress weeds
• moderate soil temperature
• free of weed seeds
• can be turned under at the end of the season

Disadvantages: 

• expensive
• can be poisonous to dogs and other wildlife
• decompose quickly
• can blow around because they’re lightweight
• may get moldy if it’s used in humid or damp conditions

Notes: 

• cocoa hull mulch must be replenished annually

Shredded newspapers or whole sheets may be used in the vegetable garden. Mulching with a layer of cardboard or paper under grass clippings is a labor-saving way to suppress weeds while naturally improving soil quality. It can also be used to keep prolific garden plants from encroaching beyond their desired location. 

Newspaper and cardboard are best for: 

• anywhere you want to suppress weeds

Depth:

• Newspaper, a few sheets thick
• Cardboard: 1 layer thick

Advantages: 

• smother weeds
• adds organic matter to improve soil
• use instead of weed fabric
• to create paths
• free

Disadvantages: 

• cardboard can be plastic coated
• cardboard can be covered in tape
• can attract bugs
• can take 3 to 6 months to breakdown in your garden

Notes:

• Always wet the newspaper as you lay it down and overlap the edges
• Soak the cardboard before laying it down to be sure that both sides are wet
• Cover the newspaper or cardboard with 2-3″ thick layer of either straw or woodchips for added protection and nutrients
• Keep the mulch and soil moist. Check to make sure that the newspaper and cardboard aren’t drying out

The advantage of evergreen boughs layered on your garden bed is that they are easy to gather up in the spring when temperatures begin to rise. Also, they do not provide a haven for burrowing voles and mice the way leaves or shredded bark can. 

Evergreen branches are best for:

• Perennials
• Small shrubs that need protection over the winter.

Depth: Several layers.

Advantages: 

• Good for insulation during the winter to prevent frost damage
• Good cover for strawberries
• Free if you have them in your yard
• Easy to gather up in the spring

Disadvantages: 

• Evergreens can be prickly, will need to wear gloves

Notes: 

• Remove them in the spring when the soil warms up and the threat of frost has passed