There are two main mulch types: biodegradable and non-biodegradable.
Biodegradable Mulches
Biodegradable mulches refer to those that can break down and release healthy nutrients into the soil to help it improve with time. You need to replace biodegradable mulch when it is rotted down. The best materials are garden compost, leaf mould, wood chippings, well rotted manure, spent hops and seaweed, to name a few.
Non-biodegradable Mulches
Non-biodegradable mulches cannot improve the structure of the soil, but they conserve moisture, suppress weeds and can look decorative. Gravel, stone chippings, pebbles and other aggregates are used as non-biodegradable mulch. Sea shells and similar materials can also be used for decorative purposes.
Woven fabrics or sheet mulches are perfect for border. When you lay them you can make slits in fabric to plant through it. The negative side of non-biodegradable mulches is that many of them do not look attractive, but you can camouflage them with gravel. To allow irrigation water to reach your plants it is better to choose permeable fabric.
So, let's start with organic types.
Biodegradable:
Shredded Bark: Shredded bark is the most inexpensive and one of the most popular types of mulch. It mostly comes from cedar trees. Shredded bark breaks down slowly, thus people use it in slopes. Sometimes, shredded bark mulch is a byproduct from other industries (it is environmentally friendly). The mulch package should have information about it.
When shredded bark decomposes it can take up nitrogen from the soil. You can add organic fertilizer to keep your plants healthy.
Leaves: You can DIY organic mulch by shredding leaves in your yard and cover the soil. Leaves should be shredded to prevent them from matting down. The best time to collect leaves is late fall.
Grass Clippings: Grass clippings is another popular type of mulch that you can either buy in a store or DIY. They break down quickly and add nitrogen to the soil. If you DIY this type of mulch, let grass clippings dry before spreading them, otherwise it will rot as it discomposes.
Do not use grass clippings from your lawn if you chemically treat it. Chemicals can harm garden plants, especially vegetables.
Straw: Straw mulch comes in a gorgeous golden color that looks great in any garden. It slowly breaks down, but you should make sure you buy quality straws. Cheap straws often result in more problems than benefits.
Compost: Compost is darker than soil and is always sets off plants nicely. Compost quickly breaks down but also adds to your soil fertility more. This type of mulch is pretty cheap and you can ask your municipality about free compost, because quite often they give it away.
Pine Needle: Pine needles can be used to add nice texture to your plantings. They stay in place longer, which is perfect for slopes. And if you use pine needle several seasons in a row it will increase the acidity of the soil. That's why people who plant acid-loving plants (for example, blueberries and rhododendrons) prefer pine needle.
Pine Bark Nuggets: Pine bark nuggets are the slowest to break down, but they do not stay in place like previous types. They are not good for slopes and areas where heavy rain can wash them away. They go in different sizes, and bigger nuggets last longer.
Wood Chips: You can contact your local tree trimmer company to see if they have free wood chips. Freshly made wood chips take up nitrogen from the soil. They can also lower the pH of the soil, which is nice for acid-lowing plants.
Wood chips made from walnut trees can contain chemicals that restrict growth of plants.
Cocoa Hull Mulch: Cocoa hull mulch looks beautiful; it delivers nice texture to your garden. Cocoa hull mulch is expensive and decomposes slowly, unlike many other types of mulch. It also does not fade and maintains rich color.
This mulch is perfect for small-leafed plants such as herbs. However, it is poisonous for cats and dogs. You should spray cocoa hull mulch with water after your spread them or they can blow away.
Colored Mulch: Organic mulch can be colored in black, red or brown. There are also other colors used, but these are the most popular. Dyes that are used to color mulch are not toxic, so you can apply it anywhere you need.
Non-Biodigradable:
Inorganic mulch refers to types of mulch that cannot break down. While homeowners prefer organic mulch, there are many inorganic options to choose from.
Plastic: Plastic mulch is made of polyethylene. This is a thin sheet which forms a thin layer above the area. Plastic is impenetrable, so sunlight, water and nutrients cannot get to your plants. This makes it perfect protection against weeds.
Plastic can also keep the heat and retain soil temperatures which are important for sprouting seeds. On the other hand, plastic cannot be used for longer than one season because it deteriorates when exposed to UV rays. Plastic mulch should be changed regularly.
Fabric: Different types of fabric are used in fabric mulch. Some prefer to use synthetic carpets, while others use landscape fabric. Unlike other inorganic mulch, fabric can last for many seasons. It does not require any special maintenance and will not bother you for many months.
The main advantage of fabric is the fact that weeds will not grow under it. It is porous and allows air and water to get to the soil. It can be combined with organic mulches or used on its own.
Gravel or River Rock: Gravel and rock do not break down in the soil and do not need to be reapplied every season. They also do not improve your soil and it can be difficult to remove rocks if you change your mind. Besides, they can make it more difficult to divide perennials.