Mulch can be a gardener's best friend. When correctly applied, it can help you spend less time weeding, less time watering and less time fighting pests. It also improves the appearance of your garden, and depending on the color and texture, it can actually be a significant element in your overall garden design. Here's what to consider when choosing organic mulch for your garden.
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What is "Organic" Mulch?
Organic mulches are made from living material (straw, bark, grass, leaves). In general, they offer greater benefits to your garden than their non-organic counterparts because as they decompose, they add nutrients to the soil and encourage earthworms-which aerate your soil and add additional nutrients.
Comparing Common Organic Mulches
There is no perfect organic mulch. When choosing mulch for your garden, consider the color, the cost, the plants you're growing and the condition of your soil.
Bark (Shredded)
Appearance: Shredded bark is generally made from cypress, cedar, redwood, or eucalyptus trees and has an attractive appearance. The color usually fades quickly.
Insulation: Good
Cost: High
Water Penetration: Fair, but may actually repel water if improperly applied.
Moisture Retention: Good
Weed Control: Fair
Depth of Application: 2-3 inches
Decomposition Rate: Very slowly. Microorganisms use nitrogen as bark decomposes. Because nitrogen is taken out of the soil during decomposition, bark should not be dug into the soil unless a high-nitrogen fertilizer is used along with the application.
Pros: Shredded bark can repel some insects; it also holds well on sloping grades and lasts several seasons before needing replacement.
Cons: Earthworms avoid redwood. The color fades quickly and applications may need to be balanced with the addition of nitrogen.
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Cocoa Bean Hulls
Appearance: Cocoa Bean hulls are by-products of the chocolate industry. They have a fine texture and a lovely dark brown appearance.
Insulation: Good
Cost: Moderate to high
Water Penetration: Good
Moisture Retention: Good
Weed Control: Fair
Depth of Application: 2-3 inches
Decomposition Rate: Rapid. Cocoa shells disappear after one season and need to be reapplied yearly.
Pros: Wonderful chocolate smell (although it fades) and nice appearance. Cocoa Bean hulls hold their color all season and will not weather like wood mulches.
Cons: Not suited for grades with a slope or in areas that experience heavy run-off. When hulls dry, they may form a crust. If applied too thickly, they get moldy. Not safe for ingestion by cats and dogs.
Grass Clippings
Appearance: Grass clippings should not be applied as mulch until they dry and turn a yellowish brown. If applied fresh (green), they can heat up enough while decomposing to harm plants.
Insulation: Good
Cost: Low
Water Penetration: Good if not matted
Moisture Retention: Good if not matted
Weed Control: Fair
Depth of Application: 1/2 inch to 1 inch maximum
Decomposition Rate: Rapid. Quickly adds nitrogen to the soil.
Pros: Grass clippings add nutrients and nitrogen to the soil quickly and are extremely inexpensive and easy to obtain.
Cons: Can contain herbicides and other chemicals from lawn care. Clippings also have the potential to introduce new seeds into your garden and if added while fresh, can heat up and cause damage to nearby plants.
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Leaves (Shredded)
Appearance: Once dry, shredded leaves are brown in color and fade over the course of time. They tend to be poor in appearance if not dried.
Insulation: Good
Cost: Like grass clippings, shredded leaves are readily available and cost effective.
Water Penetration: Fair. Can have problems with matting.
Moisture Retention: Good
Weed Control: Fair. Can have problems with matting.
Depth of Application: 4-6 inches
Decomposition Rate: Shredded leaves decompose fairly rapidly and add nitrogen into the soil. Some leaves, like oak, can slightly increase acidity levels in the soil.
Pros: Shredded leaves add organic matter and nutrients to the soil. They are inexpensive and can be added to other types of mulch.
Cons: Leaves break down quickly and have a tendency to form a mat over the soil.
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Newspaper
Appearance: Poor as a design element.
Insulation: Good
Cost: Newspaper is readily usually readily available and inexpensive.
Water Penetration: Fair
Moisture Retention: Good
Weed Control: Excellent
Depth of Application: 1 to 2 layers
Decomposition Rate: Rapid. Newspaper will generally last one season.
Pros: Newspaper provides excellent weed control, is inexpensive and readily available. It works very well when used between rows and on paths.
Cons: Newspaper works excellent as weed control, and will also inhibit new growth. If used as fall or winter mulch it needs to be removed in the spring to allow emerging growth. Needs to be held in place by heavier objects.
Peat Moss
Appearance: Has a natural, organic appearance.
Insulation: Good
Cost: Moderate to High
Water Penetration: Poor. Peat moss absorbs
water and can actually draw moisture up from the soil.
Moisture Retention:Poor. Draws moisture away from soil.
Weed Control: Good
Depth of Application: 1 inch
Decomposition Rate: Very slow
Pros:Peat moss is valuable as a soil conditioner
Cons: Peat moss adds little or no nutrients to the soil and should be used only as a soil conditioner. It also absorbs water and can draw water out of the soil rather than helping soil retain water.
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Straw
Appearance: Good if chopped.
Insulation: Good
Cost: Low to moderate depending on availability
Water Penetration: Good
Moisture Retention: Good
Weed Control: Good, but may contain weed seeds
Depth of Application: 4-8 inches
Decomposition Rate: Fairly slow. Straw is the perfect mulch for digging in at the end of the season.
Pros: Straw holds well and resists matting. It's commonly used in vegetable gardens and is one of the best mulches for strawberry plants.
Cons: Straw needs to be replaced every season and can contain weed seeds.
Wood Chips/Nuggets
Appearance: Attractive colors and textures. May retain pine or cedar scent.
Insulation: Good
Cost: Moderate to High
Water Penetration: Good
Moisture Retention: Good
Weed Control: Fair
Depth of Application: 2-4 inches
Decomposition Rate: Fairly slow. Large chips can take several seasons to decompose and don't deplete the soil of nitrogen as much as shredded bark.
Pros: Wood chips/nuggets are attractive, readily available and retain their color fairly well.
Cons: Wood chips/nuggets are not suited for sloping grades or for areas that experience heavy water run-off. Coarse nuggets are less effective at retaining moisture and weed control than finer nuggets.
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Determining How Much You Need
To figure out how much mulch you need, measure the size in square feet of the area you want to cover in your garden (multiply garden's length x width). Decide how deep you need it to be in inches (usually a minimum of 2 inches). Now multiply the square feet of the area you're covering by the depth you need in inches and divide that number by 324. The resulting number will be the amount of mulch you need in cubic yards, the measurement mulch is commonly sold in.
Mulch can be a gardener's best friend. When correctly applied, it can help you spend less time weeding, less time watering and less time fighting pests. It also improves the appearance of your garden, and depending on the color and texture, it can actually be a significant element in your overall garden design. Here's what to consider when choosing organic mulch for your garden.
