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Mulch for Weed Control and Soil Health

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Mulch provides several benefits to the garden. Luckily, adding mulch is one of the easiest gardening tasks you can undertake. The question isn't whether you should use it or not (the answer to that is a resounding Yes!) The question is, which type of mulch should you choose, and how should you apply it?

Benefits Of Mulch

Mulch is a great weed suppressant.

A nice, thick layer of mulch inhibits weeds in two important ways. First, by thoroughly covering the soil and depriving weed seeds of the light they need to germinate, mulch prevents them from gaining a foothold in the first place. Secondly, bare dirt is the perfect place for weed seeds to land and germinate. By covering all of your bare soil with mulch, most weeds will never be able to come into contact with the soil.

Mulch helps retain soil moisture.

Maintaining a consistent level of moisture in your soil is a big part of growing healthy plants. A plant that has a constant level of adequate moisture is less likely to become stressed, which means that it will be better able to resist insects and diseases. In tandem with keeping the soil moist, mulch also keeps the soil cooler in hot weather, which will prolong the amount of time it takes for many plants to bolt or go dormant. Some plants bloom best in cooler conditions, and mulch will aid in keeping these plants blooming longer.

Mulch feeds the soil.

Organic mulches (as opposed to inorganic ones like glass, plastic, or rubber) will break down over time, adding nutrients and organic matter to your soil. The worms and microbes in the soil will break down organic mulches over time, which will result in healthier soil life.

Popular Types of Mulch

The following mulches are all organic in nature, so they will nourish your soil while suppressing weeds and maintaining soil moisture. Each type has its strengths and weaknesses, and will work better in some situations than in others.

Shredded or chipped bark doesn't break down as readily, which means that it won't provide as much nutrition to your soil, but also doesn't need to be replenished as often. Some popular woods for mulch are cedar, pine, and cypress. Bark mulches work well in many settings, but are especially useful around trees and shrubs and on pathways.

Chopped leaves are plentiful and free if you have enough trees. They can be shredded by running over them a couple of times with a lawnmower or running them through a chipper/shredder. They work well on perennial beds, in vegetable gardens, and in mixed borders. They break down fairly quickly and provide plenty of nutrition to the soil.

Straw is a popular choice for vegetable gardens as well as informal paths. It has a very utilitarian look, so it probably wouldn't work in perennial borders or foundation plantings. It breaks down fairly quickly.

Grass clippings are another plentiful, free mulch. The only caveat here is to make sure that the grass hasn't been treated with chemicals—you don't want to introduce pesticides and herbicides into your organic gardens. They tend to break down very quickly, and, because they break down so fast, can actually heat up the soil rather than cooling it down. Grass clippings work well in vegetable gardens, informal mixed borders, or under a more attractive mulch, such as shredded bark or cocoa hulls.

Cocoa hulls are the most expensive of the popular mulches, but the look it provides for your garden is well worth it. Cocoa hulls have a dark brown, earth-like appearance, so you don't even notice the mulch. One of the main issues I've had with cocoa hull mulch is its tendency to develop mold in humid, wet weather. This mold doesn't harm your plants or soil, but it is unsightly.

Pine needles are another informal, and possibly free, mulch material. They look great in gardens of all kinds. However, they can be a bit acidic, so it's best to avoid using them near plants that don't tolerate acid soils very well.

Compost (including leaf mold) may be my favorite mulch material of all. Like cocoa hulls, it just fades into the plantings, so you don't even notice that it's there. Besides looking great, it provides plenty of nutrients to your soil and increases microbial activity. It will need to be replenished fairly often (at least once a year, though I usually top dress with compost in spring and fall) but if you have your own compost pile, you'll have a steady supply of black gold ready to use.

How To Apply Mulch

There is a right way and a wrong way to apply mulch. The biggest mistake people make when adding mulch is that they don't apply enough. To smother weeds and retain soil moisture, a two to three inch layer of mulch is necessary. Less than two inches of mulch will let enough light through to allow weed seeds to germinate.

In addition to applying the right amount of mulch, you also need to make sure that it isn't pushed up against your plants. Pull the mulch back from tree trunks, shrubs and the crowns of your annuals, perennials, and vegetables. Give your plants an inch or so of space. When mulch is applied up against a plant, it can hold moisture and cause the plant to rot.

Organic mulches, because they break down and improve your soil, need to be replenished from time to time. Plan on adding an additional inch of mulch to your gardens every year, either in spring or fall.

A layer of mulch can benefit every single area of your garden. Whether you have a ready-made supply, such as grass clippings or leaves, or whether you choose to order some in bulk or buy it in bags at your local garden center, the important thing is to make sure you use it. Your plants, and your soil, will appreciate it.

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Add Mulch to Your Garden
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