Mulching your beds and borders is one of the kindest things you can do for yourself and your plants. It can lower maintenance and improve the quality of your soil. Ideally, mulch is used to cover soil in new plantings until the plants grow large enough to cover the soil themselves.
What Mulch to Use?
Organic mulches are natural and plant based. They will eventually decompose and add some nutrients back into the soil. Initially however, they will use some nitrogen to breakdown. It’s a good idea to add nitrogen back using blood meal or fish meal. Inorganic mulches such as plastic sheeting, rocks, rubber chips or landscape fabric can be effective but may have maintenance issues down the road.
Shredded Composted Leaves
With the exception of the desert Southwest, I think shredded, composted leaves make excellent mulch. Instead of bagging your leaves to be taken away in the fall and buying mulch in the spring, why not make your own? Shred leaves with your mower and pile them in a bin like your compost. When spring comes you’ll have beautiful, natural looking mulch for free. Leaf litter is a component of healthy soil and provides food and shelter for wildlife.
Groundcovers are nature’s way of mulching and protecting soil from erosion. These are generally speaking perennials that are low growing and have a tendency to spread, though not aggressively. Their roots hold soil in place while their foliage cools the soil. Native groundcovers provide food and shelter for wildlife and flowers to delight the butterflies and ourselves. Best of all, you never need to reapply.
In some parts of the country pine needles are abundant and they make a good choice for mulch. They tend to “knit” together making them useful on slopes. If you always use pine needles they may make your soil slightly more acidic which can be desirable for plants like rhododendrons, azaleas and blueberries.
Straw and Hay
Straw and hay can make good mulch and is often used in vegetable gardens where it can be tilled into the soil later. Always leave some space between the plant base and the straw you’re using. Make sure the straw you buy is free of weed seeds. Otherwise, it can be more work than using nothing at all.
Pine Bark Nuggets and Shredded Bark
Both kinds of bark are commonly used mulches and are very effective. Shredded bark is preferable on slopes as it holds together well. In the same situation, heavy rain can wash good-sized nuggets of bark away. Nuggets have the advantage of decomposing more slowly.
Coco hulls have a beautiful, rich dark color but are one of the most expensive kinds of mulch to buy. It is long lasting and the color won’t fade. It seems to work best in hot, dry climates. In areas with high humidity it may grow mold on the surface. According to the ASPCA, cocoa hull is poisonous to cats and dogs if they ingest it. They go on to say however, that such cases rare.
Rocks and Gravel
Unless you are building a rock or scree garden or live in the desert, I would caution you to think twice before using rock or gravel as a mulch. While it is most certainly long lasting it is difficult to work in (think about dividing perennials) and even more difficult to remove. Rock absorbs heat during the day, releasing it at night, which increases water evaporation. Plant selection also becomes a bit tricky as only a specialized group of plants will flourish is such environments.
Landscape fabric is often used as a base layer to inhibit weed growth with some kind of mulch on top of it. If an organic mulch is chosen, say wood chips for instance, the mulch will eventually breakdown forming soil on top of the fabric where weeds will grow. It can also make future planting more difficult and is highly unattractive if the mulch layer blows or runs off.