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| Type | Minimum Depth | Advantages | Disadvantages | Durability |
| Organic Varieties | ||||
|---|---|---|---|---|
| Leaves(shredded) | 2 in/5 cm | cheap, attract earthworms | may mat down and inhibit air/water penetration if too thick | 1 season |
| Grass clippings (dry) | 2 in/5 cm | cheap, attract earthworms | may mat down and inhibit air/water penetration if too thick, compost first if sprayed with weed killer | 1 season |
| Pine needles | 3 in/6 cm | cheap, boughs are good winter mulch | may mat down and inhibit air/water penetration if too thick, will gradually raise soil acidity | 1-2 years |
| Sawdust | 2 in/5 cm | cheap, attracts earthworms | do not use near buildings (termites), acidic: compost first or mix with nitrogen | 1-2 years |
| Wood Chips (home made) | 2 in/5 cm | decompose slowly, improve soil | do not use near buildings (termites) | 1 season |
| Straw | 4 in/10 cm | attracts worms, good winter mulch | may contain seeds & some diseases | Reapply 2x/season |
| Bark (commercial) | 2 in/5 cm | decomposes slowly; attractive | do not use near buildings (termites), expensive | 1-2 years |
| Inorganic Varieties | ||||
| Plastic | 6 mils | stops weed growth until tears or decomposes | allows no air or water to soil/roots, raises soil temps, expensive | 1-2 years |
| Landscaping Cloth | 6 mils | allows air/water to soil, suppresses most weeds | cover with light top mulch to delay deterioration, expensive | Indefinite |
| Newspaper | 3 sheets | cheap, prevents weed germination | needs top cover to prevent blowing away, can’t use color sections | 1 season |
| Lava/Stone | 2 in/5 cm | formal look, permanent | allows weed growth, expensive, lava is light and washes away | Indefinite |
| Rubber | 2 in/5 cm | low fade colors, permanent | raises soil temps, very expensive | Indefinite |
Step Two: How Much?
This is really three questions:
The quantity needed is calculated by: length of plot x width of plot x depth of mulch = cubic volume needed. For example, a 10 ft x 15 ft garden with 2 in. deep mulch is 10 ft x 15 ft x .17 ft (2 in = 2/12 or .17 ft), which equals 25 cu. ft. needed. To convert to cubic yards, divide by 27. If you work in metric measure, simply use meters for all dimensions.
The time it takes to acquire your materials depends on whether you do it yourself or purchase it. Raking, chipping and shredding takes time. But so does a trip to the store, plus the time it took you to earn the money for the purchase. If you don’t have enough free organic material available, you may choose to make some and buy some.
Cost considerations should consider both time and money. If one choice needs less time commitment because it is permanent like stone, balance that against a higher initial monetary cost. Do you need to do something with your leaves anyway? Perhaps shredding them with a mower or in a barrel using a trimmer and saving them until they can be applied is a more efficient use of your time than bagging them for disposal in the Fall and then buying wood chips in the Spring.
Step Three: How to Get the Best Results
This depends on whether your application is for a growing season or a dormant season. There are also some special considerations for grass, in particular soil types and around buildings.
During Growing Season
In Spring wait until temperatures have been above 70 F for two weeks before adding mulch to your vegetable or flower beds. Early season annuals like pansies or daffodils are fine once shoots appear. This will ensure that you do not inhibit seed growth or contribute to decay by locking in cooler soil temperatures.
During Dormant Season
These applications reduce erosion, moisture loss and plant injury from frost heaving. Wait until after several hard freezes below 20 F/ -7 C, but before consistently cold weather arrives. This will allow the plants to ready themselves while discouraging rodents from nesting in your garden area, as they will already have found another nest. Use loose material such as pine boughs or straw which will not compact under snow.
Special Considerations
Be sure to dry any grass clippings before application, and either compost or avoid altogether any herbicide or pesticide treated grass. To balance its nitrogen content, mix grass with some carbon-containing composting material such as chopped leaves, shredded newspaper or pine needles.
Do not place any mulch in contact with plant stems, as this may promote rot.
Next to buildings, avoid using either wood or bark since termites may find this attractive and then migrate to your home. Likewise, reflective white stone near a building will add heat during Summer months, so use dark stone here.
Finally, avoid using mulch over poorly drained soils. Since mulch promotes water retention, you will only be risking root rot. If you feel it necessary, use only a coarse variety.
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