Spreading mulch over your garden soil is the best way to save time and energy in your yard. Mulch helps the soil hold moisture so you don't have to water as often. It also suppresses weeds. And over time, mulches made from organic materials break down and increase your soil's structure and fertility.
Shredded bark is one of the most common and least expensive mulches. It comes from a variety of sources, including cedar trees. Shredded bark is one of the best mulch types to use on slopes and it breaks down relatively slowly. Some shredded-bark products are byproducts from other industries; they're considered environmentally friendly. Check the mulch packaging for more information.
Here's a hint: Shredded bark can take up some nitrogen from the soil as it decomposes. If you have poor soil, adding some organic fertilizer to the soil can help keep your plants healthy.
Save money by shredding fallen leaves in your yard and using them to cover the soil. Fallen leaves break down quickly (often in less than a year), but should be shredded before use to prevent them from matting down. Fallen leaves are commonly used as mulch in winter.
Another mulch you can make for free, grass clippings break down fast but add nitrogen to the soil as they do. It's best to use grass clippings in thin layers or to let the grass dry before spreading it as a mulch -- otherwise it starts to stink and rot as it decomposes.
Here's a hint: Avoid using grass clippings if your lawn is chemically treated, especially if you use it in vegetable gardens. The chemicals may harm your desirable garden plants.
Straw has a beautiful golden color that looks great in the garden. It's also a bit slower to break down than leaves or grass clippings. But you do need to make sure the straw is free of weed seeds, otherwise it can cause more weeds than it prevents. (Oat straw is often particularly weedy.)
Compost looks like soil, except it's darker, so it really sets off plants well. This mulch material breaks down quickly but adds to your soil structure the fastest. Plus, it's inexpensive; you can create your own rich compost for free. Many municipalities give away compost, as well.
Pine needles add a delicate, fine texture to plantings. They hold in place well, making them useful on slopes, and they're relatively slow to break down. If you continuously use pine needles as mulch, they may increase the acidity of your soil. This makes them ideal for use with acid-loving plants such as azaleas, rhododendrons, blueberries, and some types of conifers.
Pine Bark Nuggets
Pine bark nuggets are slower to break down than shredded bark, but they don't stay in place as well. They're not a good choice for slopes or other areas where they may be washed away by heavy rain. Pine bark nuggets are available in a variety of sizes; the bigger the nugget, the longer it lasts.
You can often get wood chips for free from local tree trimmers, though the trimmers will usually ask you to haul the chips yourself. Wood chips, especially when they're freshly made, can take up a fair amount of nitrogen from the soil. They can be acidic and lower your soil's pH, as well.
Here's a hint: If you get wood chips from a local source, check if the tree had poison ivy on it. Working with wood chips that contain poison ivy can cause skin irritation. Also: Wood chips from walnut trees may contain natural chemicals that inhibit the growth of many garden plants.
Cocoa Hull Mulch
Cocoa hull mulch is one of the most beautiful, thanks to its fine texture and rich color. And many gardeners appreciate its delightful chocolate fragrance. Cocoa hull mulch is one of the most expensive mulch types, though. It decomposes slowly, and unlike most mulch types, it doesn't fade with time. It's a great mulch for small-leafed plants such as herbs where the shells are easy to work around. In areas with hot, humid weather, mold may grow on its surface. Cocoa hull mulch is poisonous to dogs and cats if they eat it.
Here's a hint: Because cocoa hulls are light, they can blow away unless you spray them down well with water after you first spread them.
Gravel or River Rock
Because they're inorganic materials, gravel and river rock don't break down in the landscape, so they don't need to be reapplied every year. However, it also means they don't improve your soil over time.
Here's a hint: It can be very difficult to remove gravel or river rock mulch if you ever change your mind. They can make it more difficult to plant in or divide perennials.