What kind of mulch should I use? Wintertime for the gardener is planning time. When snow comes and the frigid winter winds keep us from tinkering in the garden shed, we curl up on the couch with seed catalogs, garden magazines, and design ideas. It is usually in the spring we start thinking about mulches and groundcovers. But winter is a good time to learn and plan on what mulches we want to use, either to update existing gardens or for adding new.
There are a plethora of choices for mulch. However, we need to remember that each region of the United States has its own availability of mulch choices. Because we are talking about organic mulch, we can leave out things like rock and rubber. On the west coast you may find redwood and pine mulches, by the gulf it may be cypress.
Here in the Great Plains and Midwest regions, we find cedar, hardwood, sawdust, and alfalfa mulches. Let us discuss those.
This is probably the most commonly used mulch here in the Central Great Plains. We have an overabundance of eastern red cedar trees, which is where cedar mulch comes from. There is a mill for it in southern Kansas, as well as others throughout the region. It is cheap and you can buy in by the bag or bulk. We sell it here both ways.
Cedar mulch is chunky, with pieces in size from 1 to 4 inches long by 1/2 to 1 inch wide. When first laid down, cedar mulch is golden in color, but fades in 1 year to a grayish tan. It is easy to lay down, but can be difficult to make smooth. I like to use a metal leaf rake, turned upside-down to smooth out mulch clumps, but cedar is tricky.
One of the benefits besides cost is that cedar mulch can help keep weeds and pests down. Cedar has both aromatic and allelopathic compounds in the oils of the bark and wood. These chemical compounds suppress some weeds ability to germinate and grow. The aromatics in the oils also deter some moths, beetles, and other pest insects.
What I do not like about cedar is that it does a poor job of holding in soil moisture. This is one of the main reasons we use mulches on landscapes. Because of the density of the wood and bark mixed in the cedar mulch, there is a lot of pore space, creating more air movement through the material. This results in more air reaching the soil surface.
Mulches labeled as hardwood tend to be dyed with colors such as black, brown, or red. I get a lot of calls for red mulches in Nebraska, and dark brown mulch everywhere else. These mulches can be great color addition to the garden or walkway and can help plants pop out in the garden.
However, dyed mulches are chemically colored and these chemical colors can leach into the ground and be detrimental to the garden. I generally only recommend using dyed mulches on permanent walkways or where there are few if any plants.
Hardwood mulches can be chipped from any source, including recycled pallets or brush brought to the recycling yard. The problem is that pallets are often treated with chemicals to reduce rot and these chemicals can affect plant health. Hardwoods like oak, hickory, and walnut have natural allelopathic compound which inhibit plant growth.
Therefore, if you must use hardwood mulches, use them where you have no plantings but need a mulched surface, such as walkways, parking areas, or strips along buildings to keep back plant growth.
We started using sawdust mulch about 7 years ago. It comes from a local company and is the ground cover for their hog trailers. They apply this mulch to the inside of their trailers. Then, after hauling hogs to market, they dump the mulch out into piles at a recycling facility where we pick it up.
This mulch is finely chopped pine and cedar flakes, which we call sawdust. It has been heated with hog manure and urine, and retains the moisture that it collects from watering and rain. While it may not sound like something you would want in your garden, we recommend it.
We have done various testing and trialing to determine if there are any lasting parasites or diseases being transferred from the mulch to garden plants, and have found nothing. This mulch is easy to lay down, easy to make smooth, and give a natural fertilizer boost to the plants. Also, it retains moisture and does a great job of retaining soil moisture.
We usually apply sawdust 4 to 6 inches deep and it compacts down to 3 to 4 inches. At this rate, it breaks down and composts in about 18 months, so another application is necessary every other year. But it is very cheap, and we sell a lot of it. The color is dark brown to tan-brown and does not age to gray.
This organic mulch is produced by a local grower in our region. They chop alfalfa into small clippings and bag it for sale. Alfalfa mulch is lightweight, but the particles lock together when laid down and watered, holding in moisture very well.
The biggest drawback to alfalfa is the cost. It is expensive. I recommend using alfalfa for annual plantings of flowers and vegetables. It has minerals and nitrogen that helps plants grow. I would not use alfalfa over the whole landscape unless you had really poor soil which needed amending.
Other Organic Mulches
The above mulches are the most used and most recommended mulches in the Central Great Plains and Midwest regions. However, if you are shopping for mulch at most garden centers or big box stores, you may see the following other organic mulches as well.
This mulch is from the logging industry in the southeast United States and comes from cypress trees. Cypress mulch lasts as long as cedar and has similar allelopathic and aromatic compounds. However, cypress is not a regional choice and does not support local logging, trucking, or shipping companies.
This organic mulch is by-product of the chocolate industry. Cacao beans are shelled (hulled) and the hulls are packaged to use as mulch. They are very lightweight and should only be used in areas that get little wind. They do have a chocolate-like aroma, but are not toxic to dogs. Cocoa hulls as mulch are expensive, more even than alfalfa mulch.
Pine Straw Mulch
Pine needles straw is used as mulch mainly in the southeast and along the gulf states where it is common. They slowly acidify the soil, not quickly as is sometimes reported. When applying it takes more than other mulches to cover the same area because the needles are thin. They do not do a good job of retaining soil moisture unless they have been chopped.
Pine Bark Mulch
This mulch is made by shredded pine bark into different size chunks or nuggets. There are usually 2 sizes available; small and large. Small pine bark nuggets are 1/2 to 1 inch long by wide. It makes a nice, dark brown mulch that lasts for at least 2 seasons, but it does fade to gray in 1 year. The bigger size is 2 to 4 inches wide and long.
Tips for Spreading Organic Mulches
- When spreading organic mulches, lay down at least 3 inches of mulch. Never lay less than 3 inches and try not to lay more than 6 inches.
- Use a metal, spring-type leaf rake, upside-down to smooth out fine mulches like sawdust, cocoa hulls, and pine bark. A hard garden rake, turned upside-down can be used for smoothing out cedar, cypress, and hardwood mulches.
- Use a wheelbarrow to move bulk or bagged mulches.
- Leave a space of 3 to 8 inches between the mulch and plants. Shrubs and trees should have the largest spacing, while perennials can be closer.
- Never pile mulch on top of plants.
Now you can decide which mulches to add to your garden or walkway. Knowing this helps you in the long run, as mulches are beneficial in retaining soil moisture and preventing excessive weed growth.