Mulch is generally sold in bulk by the cubic yard. Remember from last month, never put more than 4 inches thick (3 inches is better) total including existing mulch, or nutrients, water and air can’t penetrate and mold or diseases may develop. 

How to calculate the mulch needed:

1. Measure area to mulch. Multiply length (feet) by width (feet)
2. Divide by 27
3. Divide by 12
4. Multiply this answer by the depth desired (2 or 3 inches)
5. This is the total number of cubic yards to order
1. 20 ft x 30 ft garden = 600 sq ft area
2. 600 divided by 27 = 22.22
3. 22.22 divided by 12 = 1.85
4. 1.85 x 3 (inches deep) = 5.55 or order 6 cubic yards

What are some recommended mulches? Mulch differs in availability by area. Look around your neighborhood and see what works successfully year after year, not just when it is first applied.

Organic mulches are best for the environment and your plants. They break down, which is good for the soil in most cases and must be replaced. A rule of thumb is the finer the material the quicker it breaks down.

Straw is good winter protection, but if left on the garden additional nitrogen must be added. Shredded leaves are free and a nice mulch (whole leaves mat and don’t allow water and nutrients to penetrate), but nitrogen must also be added. Black walnut, camphor and eucalyptus leaves contain substances that inhibit growth and shouldn’t be used. Shredded hardwood bark is popular and useful as are the relatively new double and triple shredded bark. The black lovely looking triple shredded bark can be used as planting soil, but it breaks down rapidly and needs to be replaced frequently.

Mulches that don’t break down and should be avoided include the new designer colored rubber. Studies, not funded by the rubber industry, have found these mulches are dangerous to plants, soil and possibly children and they stink. They are touted as recycled, but elevated zinc levels along with cadmium, arsenic and other trace heavy metals can be present. I would stay away from them until further research and regulations are present. Read your regular mulch bags and make sure crumb rubber fillers aren’t included!

Also, beware of cocoa mulch with dogs and other animals. If they ingest this mulch, which smells sweet, compounds found in chocolate (theobromine and caffeine) can be hazardous and even deadly to them. And, please, don’t put white rocks as mulch. It is aesthetically ugly (author’s opinion), doesn’t decompose or help plants, looks dirty because soil splashes during rains, is expensive and it can heat up and cook plants.

Go forth and mulch!

Next month, part three…final in series…Do’s and Don’ts of mulch!

Sandie is a freelance writer and photographer. Her mother started her passion for gardening by "letting" her help her plant and water annuals, paint stepping stones and mow and edge the grass. Some of the "dirt" must have been absorbed. She consider herself to be a plant collector. Her garden had a plan, but it has been overrun by cool and not so cool plants. If they grow and bloom or look nice, they stay. That includes what many people might call weeds! Sandie calls them wildflowers or native plants. Check out her website at www.SandieParrott.com for more info. She currently writes garden articles and profiles of passionate gardeners for "the Michigan Gardener" and "the Herbarist" along with other non-gardening writing. 

User Guides (Slide)