The use of primarily bark mulch in the landscape has been common now for years. The benefits of mulches include the retention of soil moisture, suppression of weed seed germination and the aesthetic appeal of a freshly mulched area. With so many types of mulch available, what is the best one to use? Well, it depends.
Hardwood bark mulch that is hammer-milled into uniform pieces is probably the most common as it is relatively inexpensive, has an appealing dark brown color and is readily available in bulk or as a bagged product. Hardwood bulk mulch is usually applied around trees and shrubs at a depth of 2-3 inches and about 1-2 inches deep around herbaceous perennials and annual flowers. As long as it is not applied too deeply and the nitrogen starvation to plants during this mulch’s decomposition is compensated by adding additional nitrogen in the form of a garden fertilizer like 10-10-10, this mulch works great.
Pine bark mulch is generally lighter and consists of finer particles than hardwood and is easier to spread around small plants than hardwood. Generally, pine bark mulch is available in a bagged product and not so much in bulk. Another form of pine bark is that of pine bark nuggets or mini nuggets. The larger particle size has great aesthetic appeal in some landscape settings.
Cypress mulch is somewhat common and has a great smell and is usually, like pine, available as a bagged product. The reddish-brown color of cypress, appeals to the eye along with this mulch decomposing slower than hardwood or pine. In recent years though, some controversy has arisen from the use of cypress mulch because of the harvest of younger trees to be turned into mulch instead of the mulch resulting as a by-product of the lumber industry.
Another mulch is the product known as Sweet Peet, which is not peat at all but largely made up of composted horse manure and other proprietary ingredients according to the Sweet Peet people. Sweet Peet when used as a mulch, is denser than most other mulches so that it need not be spread as thick. The very dark brown to black color of Sweet Peet is pleasing in a garden setting. Usually, Sweet Peet is spread to a depth of about 2 inches deep around trees and shrubs and about 1 inch deep around annual flowers and herbaceous perennials. The lesser depth needed compared to other mulches makes it cost competitive to most other mulches. Another cost advantage is Sweet Peet in bulk can be as much as $100 less per cubic yard than the equivalent amount of 1.5 ft³ bags when larger quantities of Sweet Peet are needed. One more advantage of Sweet Peet over bark mulches is that it does not “rob” the soil of nitrogen but instead supplies nitrogen to the soil and plants. The above fact is especially noticed when nitrogen-hungry annual flowers have Sweet Peet as a mulch as they seem to thrive compared to bark mulches that “steal” nitrogen from the soil. While there are many other mulches that can be found, the ones mentioned in this article are ones used mainly in this area. A few rules of mulching are given below:
- Never mulch too early in the spring, as cold wet soil will remain wetter and colder longer which is detrimental to plant root growth.
- Never over mulch, as mulch piled too deeply around plants can cause bark cracking and even death among larger trees such as some are now mulched in what are called volcano mounds.
- Never mulch with hardwood bark mulch that has a strong manure or vinegar smell as this mulch is severely acid from the action of anaerobic bacteria that produce vinegar. Mulching of young plants can cause death and sometimes the death of older trees up to 2-3 inches of the trunk caliper when acid mulch is used.
- For larger quantities, picking up mulch in bulk yourself is best as you are able to see the quality or sometimes the lack thereof, as well as saving money.
- For bark mulches, especially hardwood bark mulch, an addition of 1 lb. of actual nitrogen per 1000 ft² in a landscape bed will overcome the nitrogen “pull” of the mulch causing stunting of growth of the plants. A fertilizer such as 10-10-10 applied at 10 lbs./1000 ft² will accomplish the 1 lb. of actual nitrogen rule. Applying the fertilizer around May 1st, July 1st and October 15th is all that is needed. Just be sure to brush any fertilizer off the plant foliage.
- Calculate the amount of mulch by using the following formula: (Area in square feet) * x/12 = cubic feet needed where “x” is the depth in inches of the mulch desired. To get cubic yards needed, just divide the number of cubic feet by the number 27. For example a landscape bed of 4 ft. wide by 25 ft. long has an
area of 100 ft.² with the desired mulch depth of 3 inches. Using the formula 100 ft² x 3″/12″ = 25 cubic feet divided by 27, the cubic yards needed is .93 which is rounded to 1 cubic yard.
By following the few simple rules above, the benefits of mulch greatly outweigh a few disadvantages, so why not mulch!