The general rule of thumb is to spread mulch about two to four inches thick over the soil surface. When mulch is too thick, it can be counterproductive and prevent water from reaching the soil. On the flip side, too thin a layer of mulch may not adequately stop weed growth or prevent evaporation as intended.
When spreading your mulch, it's very important to keep the mulch three inches away from the base of your plants and the trunks of trees (no mulch volcanos!) Keeping distance between plants and mulch helps to avoid plant rot and other diseases, prevents nesting grounds for insects, and promotes air circulation.
Focus on getting the bulk of the area. The next step is to decide how deep you would like the mulch to be. We recommend that you spread 1-2 inches of mulch per year.
Since one function of mulch is preservation of moisture, just after a light rainfall is considered a great time to apply mulch as long as ground is not completely waterlogged.
After you've created a base layer of topsoil, then enriched it with compost, you need a cover to keep it cool and moist, and prevent weeds from competing with the more desirable plants in your garden. This is where mulch comes in.
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.
Knowing how much mulch to use can be tricky. A 1-inch to 2-inch layer of fine mulch should be sufficient, while a coarser material should be 3 to 4 inches deep. Too much of either type can suffocate your plants. In areas where you simply want to keep anything from growing, you can lay it on as thick as you like.
Our view is that mulch should be put down annually to compensate for the decomposition of the wood and bark fiber and the graying of the color. When applying annually, a 2”- 3” layer of mulch should be a sufficient depth. Mulch that is applied too thick can suffocate your plants and starve your soil for moisture.
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So, should you remove old mulch? Expert green thumbs contend that getting rid of last year's mulch is completely unnecessary. Mulch gradually breaks down, adding beneficial nutrients and other organic matter to the soil. Removing pre-existing mulch every year only ends up to be extra work and a needless expense.
Brown mulch is a neutral choice that many homeowners opt for. It can easily complement homes and gardens of all colors, helping both light and dark plants to appear more vibrant. If the elements of your home feature a variety of colors and shades, brown is a universal choice that can bring unity to your outdoor space.
One of the best mulches to prevent weeds in your garden is wood chips, also known as wooden mulch. Wood chips, including graded fine bark or pine mulch, won't decompose as quickly as other mulch types, giving you a long-term solution to weed control.
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.
Plant problems caused by too much mulch
Excessive mulch reduces soil oxygen for roots, suffocating them and causing them to die. Roots in search of oxygen and water sometimes grow into excess mulch. During dry periods the mulch dries out and the roots in the mulch die.
All organic mulch breaks down and eventually turns into soil. Mulch will become ineffective at suppressing weeds as it becomes compost. Below the compost layer, is what used to be composted mulch, but is now soil. As mulch is topped up every year, the layers of mulch, to compost, to soil will keep building.
Landscape fabric is not needed beneath mulch to block weeds, if you have the correct amount of mulch. Also, as the mulch breaks down, the nutrients and compost cannot do their job of helping the plants' roots and weeds end up seeding into the compst on top of the fabric.
How deep should I mulch? Mulch should be applied to a depth of 100mm. This will provide an effective weed suppressing layer and maximize moisture retention. Should customers wish to apply less than 100mm we recommend using Weedmat prior to mulching.
Do not install if rain is in the forecast. As noted above, you should try to find a window of no less than 48 hours of rain-free weather as critical drying time is needed.
To smother the weeds and retain moisture within the soil, the layer of mulch needs to be at least 3 inches thick but no more than 3 inches or you could do damage to tree trunks and shrubs. Even two inches of mulch can let through enough sunlight allowing weed seeds to germinate.
Using a rake or gloved hands, smooth out the small mounds of mulch to the desired depth of 2- to 4-inches. Leave at least one inch between mulch and any tree trunks or plants so root systems have necessary space to circulate air and water, being careful not to suffocate existing plant growth.
The practical life-time of mulch can be anywhere from 4-7 years. This is how long it takes for a layer of mulch to completely break down, although it depends on a number of different environmental factors (e.g. in direct sunlight, covering very wet ground etc).