Here at Gardening Know How we get lots of garden-related questions, and we strive to answer them in an easy-to-understand way. This includes mulch. The following information includes the 10 most commonly asked questions we’ve encountered with regards to mulch.
In nature, leaves that fall in the forest protect understory plants through the winter and add rich organic matter to the forest floor. Ground or shredded leaves make an excellent mulch for established trees, shrubs and flowerbeds. In fact, 50-80% of nutrients in a plant accumulate in its leaves. When you repurpose leaves by using them as mulch, you are adding nutrient rich organic matter to the beds. However, because some of these nutrients are in such high concentrates, it is recommended that you allow leaf mulch to sit for a while or compost it before using it around young plants which may burn. Shredded leaf mulch is also excellent for loosening up heavy clay soils. Leaves should be ground or shredded with a mower or mulcher before using as mulch.
Mushrooms tend to grow in areas that are very moist or damp, and also very fertile. Fungi help to breakdown decomposing materials…meaning if you see fungi forming on your mulch, it is probably decomposing into rich organic matter. While these mulch mushrooms are usually harmless, they may be a sign that you need to refresh your mulch. Raking and stirring up the mulch can also temporarily disrupt mushroom colony formation. You may also need to adjust your watering habits, to provide water directly to the root zones of plants without wetting the rest of the garden. Also, it may be necessary to do some trimming and pruning to increase air flow and sunlight to the area.
Little flying insects that hang around mulched beds are usually just fungus gnats, which are attracted to moist, decaying materials. Just as with those found in houseplants, fungus gnats don’t bother with the living tissues of plants. They feed on moist, decaying matter instead, such as decomposing mulch, fallen leaves or other garden debris. Raking mulch around or topping it with fresh, dry mulch can help get rid of fungus gnats. Also, try not to let the mulched beds stay too damp and moist. Watering plants directly at their root zone can prevent excessive moisture in the garden.
When using fresh mulch from a recently cut down tree, it is recommended that you allow this mulch to sit and cure for a while before applying it around young, newly installed plants. This is because wood chips let off high levels of nitrogen that can burn tender plants. Generally, it is not deemed necessary to treat new wood chips for pests or diseases. It is very unlikely that pests or diseases would spread from wood chips to garden plants.
Commercial dyed mulches must comply with government safety standards….meaning that if you’ve bought red mulch from a reputable business, the dye used on it is non-toxic. Cats generally don’t eat mulch, but they can be a nuisance by using freshly mulched beds as a litter box. Dogs, on the other hand, sometimes chew on wood chips in the landscape. Usually, they do this because of some sort of nutrient deficiency. If you see Fido chewing on mulch every time he’s outside, you should probably contact your vet. Although mulch dyes are usually non-toxic, the sharp wood chips can cause internal damage to dogs who eat them. Always watch and monitor your pet’s outdoor activities to ensure their safety around mulch.
Using hay or grass clippings as mulch can be an excellent cheap or free alternative to traditional mulch. However, hay may contain a lot of weed seeds. This can result in more work for the gardener, so try to use only hay from locations that you know have few weeds. Hay or grass clippings can also break down much more quickly than wood mulches. This will mean more frequent applications. It is recommended that fresh clippings be spread thinly on gardens, as they can become smelly and slimy as they decompose. Dried clippings can be applied deeper.
As a landscape designer, I hate to see a landscape bed with landscape fabric poking out of thin layers of mulch. According to most reputable resources in the field, anywhere from 1-4 inches (2.5-10 cm.) is the recommended depth of mulch application for flower beds. I, personally, always recommend a depth of 3 inches (7.6 cm.) to my customers, as this amount of mulch is a perfect depth to suppress weeds and retain cooling moisture around plant roots.
As shredded pine bark sits on a garden bed, slowly breaking down, it begins to form almost a crust over the garden. The more it is raked or turned, the less likely it is to meld together, so sometimes being patient and leaving the mulch alone will cause it to withstand wind better. Wood chip mulch does not meld together like shredded bark, though, and may not be suitable for windy sites. Alternatives to wood mulches that can blow are to use rock mulches or low growing groundcovers in windy locations.
Controlling weeds in mulch need not be difficult. Applying a pre-emergent herbicide to mulched beds in early spring can help suppress many weeds before they sprout up. However, this only works on weeds before they emerge. Contractor grade weed control fabric beneath the mulch can also prevent a lot of weeds. However, in time even the best quality fabric can rip or break down. Aggressive weeds can poke through fabric and cause more tearing as they are pulled out. There are also herbicides that specifically kill grass but not ornamental plants. These can be carefully sprayed on unwanted grass weeds as they pop up in flowerbeds. Generally, a combination of pre-emergent herbicides, weed fabric, RTU spray herbicides and hand pulling weeds will be necessary in any mulched flower or landscape bed.
Newspapers, cardboard, grass clippings, fallen leaves and homemade composts are some things you can repurpose for free or very inexpensive mulch. Straw or hay can also be acquired at very low costs to use as mulch. Many cities or townships offer wood chips or compost to residents at low costs. Arborists and tree services may also sell inexpensive wood chips or shredded bark. Rock or rubber mulches tend to be the most expensive mulch choices.
We all have questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We’re always here to help.