Mulch plays an important role in your landscape. Proper mulch application provides benefits to water retention, soil temperature, weed inhibition, and soil erosion. These qualities can help reduce fuel risk in fire prone areas, but also introduces a new combustible material into your landscape. For this reason, it is important to consider the type, location, and quantity of mulch used.
Maintaining noncombustible, ignition–resistant areas immediately adjacent to structures (within 5 ft) is particularly important. Embers often accumulate in these areas, providing an ignition source for combustible materials. Further away from the structure, mulch-covered areas should be separated by noncombustible materials. This is to prevent the mulch, if ignited, from spreading the fire in a continuous manner.
Irrigating wood and bark mulches should not be relied upon to lessen fire hazard. Irrigation does reduce the ignitability of mulches, but water supply and pressure may be limited or unavailable during a wildfire. Furthermore, the dry, hot and windy weather seen during wildfires will dry out the mulch bed well in advance of the flaming front.
Material options
Composted Wood Chips under 3 inches in size, should be applied 2-4 inches deep. This material has low burn characteristics, but may smolder. Smoldering combustion produced by this mulch treatment may not be readily noticeable during a wildfire event and may go undetected by firefighters.
Rice Straw or Coconut Fiber mulches are often the most effective treatment to protect gentle slopes from erosion. Find more information about installing post fire erosion control here.
Shredded Rubber, Pine Needles and Shredded Cedar Bark have among the highest hazardous combustion characteristics and are recommended for use only in areas more than 30 feet from the house. Although shredded rubber is not a natural woody mulch, it is still flammable and will smolder and flame. It should be limited to use under play equipment and more than 30 feet from structures.
Paving Stones, Gravel, and Decomposed Granite are non-combustible and should be used within 5 feet of the home, along pathways, and to segment patches of combustible vegetation.
References
Check out these additional wildfire preparedness resources from UC ANR Fire Network Members and our colleagues!
Mulch flammability
FAQs
Mulch helps conserve and extend available water, protects the soil from erosion, reduces competition by suppressing weeds, moderates temperature extremes, and acts as a barrier or visible marker of gardening beds to limit damage by landscape maintenance equipment.
What is the disadvantage of mulching? ›
Disadvantages of Mulching
Excessive mulch that is a layer more than 3 inches deep can suffocate and bury plants. In this case, oxygen and water are unable to reach the roots. A layer of 2 to 3 inches of mulch is enough.
What is the best mulch to use? ›
But, generally, using organic mulch made from wood chips or bark will be the best choice. It's one of the easiest and least expensive ways to ensure the long-term health and fertility of your soil and the health of your trees and shrubs.
What is mulch for soil? ›
What is mulching? Mulching your garden is when you add a thick layer of organic matter (usually manure, compost or bark) on the surface, this will help to retain soil moisture, suppress weeds, add nutrients and insulate plant roots.
What is the best time to put down mulch? ›
In general, mid- to late-spring is mulching season; this is when the soil is warming up from the freezing temperatures it experienced all winter. Mulching too early will slow down the warming process, which the soil needs to do its job.
Does mulch attract termites? ›
The presence of mulch in your yard might not mean you're going to get termites, but it does mean that you're increasing your risk. The best way to decrease the risk of termites in mulch is to maintain a long-term termite prevention and control with a pest management professional.
When not to use mulch? ›
When Not to Mulch. Don't mulch just before major rainfall is expected. Too much rain might cause your mulch to run right off your flower beds or away from the base of a tree. You also shouldn't mulch right before a very windy day.
Is it better to mulch or not? ›
Most of the time, mulching your clippings is the best option. You should bag your clippings if the grass is tall, leaves are covering the lawn, or you need to prevent disease and weeds from spreading.
Can old mulch be reused? ›
If it still looks like mulch, you can reuse it. If it resembles dirt, it's lost its functionality as mulch. If it smells of vinegar, rotten eggs, or alcohol (“sour mulch”) it is temporarily unusable until it's rinsed and dried. If the mulch has any signs of disease, fungus, or parasites, it should be disposed of.
What color mulch lasts longer? ›
Over time, mulch colors fade due to frequent exposure to sunlight. Regular non-dyed mulch may become a grayish color in one to two months, while dyed brown or black mulches may keep their color for a year or longer.
Brown mulch is a nice touch to any lawn and garden, and its natural color makes both light and darker-colored plants appear vibrant when paired together. This color mulch works well in small areas, but tends to lose its beautiful color after just one season.
What plants don't like mulch? ›
There are some species that tolerate excessive mulch better than others. Some of the worst effected plants are grassy plants (iris, daylilies, liriope, etc.), Indian Hawthorn, Azaleas and Loropetalum.
Should I water mulch after putting it down? ›
You should spread your mulch to be two to four inches thick. If your mulch is too thin, then weeds can push through. If your mulch is too thick, it prevents water from reaching the soil. Water after mulching — This is an optional step, but a final watering can help settle the mulch into place.
Can you put mulch directly on soil? ›
Greg Baka, a long-time gardener and the owner of Easy Digging tools, notes that it's OK to mix compost into your topsoil to improve it, but let bark mulch lie on the surface of your soil. "Mulch mixed with soil causes difficulties in digging and weeding," Baka explains.
Is mulch really necessary? ›
Mulch can mitigate soil compaction, and it is better than bare soil at capturing water and fostering water penetration, so it reduces runoff. It also slows water evaporation from the underlying soil by up to 35 percent, Dr. Fonteno said, and it moderates soil temperatures in the summer and winter.
Does mulching really help? ›
Mulching grass clippings provides more nutrients for your soil. As they break down, the clippings will release nitrogen, potassium, and phosphorus. These are essential nutrients that your lawn needs to stay healthy.
Does mulch turn into soil? ›
Over time, mulch will break down and effectively become topsoil but it shouldn't be used in lieu of topsoil. That said, while you could leave your topsoil uncovered, it is wise to cover it with mulch to avoid erosion from the rain and overheating from our hot sun.
