Every year I spend lots of time installing mulch into gardens. It is hard dirty work but it does make a big difference in the appearance of a garden. There are two types of mulch, organic and inorganic. What is the difference? Organic mulch breaks down and helps to improve the soil such as pine needles, wood chips, pine bark, tree trimmings, grass clippings, compost and straw.
Inorganic mulch do not add nutrients to the soil and do not decompose quickly. Inorganic mulch would be stone, pebbles, gravel or recycled rubber tires. Consider using a weed barrier under inorganic mulch. It is easier to remove the mulch in the future if you decide you do not want it. Weed barrier is sold in different sizes, weights and years that it will last. Every type of mulch has it's place and use, but carefully consider the types of plants that you select and will be growing with the mulch. In my zone 5 area, I prefer hardwood mulch. It has good color and is complimentary to all colors of garden plants. It breaks down quickly, helps retain moisture in the soil and decreases weed growth (you will always have some weed growth in all mulches). I hear many people say they want a lush cottage garden. Remember that mulch decreases weed seed growth and it will also decrease flower seed growth. Most people think that mulch will prevent weed growth and pile it on far deeper than it should be. For gardens, 2 to 3 inches deep of organic mulch is sufficient. For all the good that mulch can do it also has it's problems. Many people mulch every year to get the color back that has faded from sunlight. They continue to apply until the wood mulch is way to deep. The wood mulch mats down and when it rains or the sprinkler system comes on the water runs off the mulch rather than soaking down to the roots of the plants. People with sprinkler systems often have many of the roots of their plants growing or exposed in the mulch and not down in the soil like they should be. Wood mulch can also become the home for rodents and insects that can damage stems, branches or trunks of your plants. It is also the perfect environment in the spring for many types of mushrooms and fungi. Many plants may not like living in the heat that can be generated by rock mulch and pulling weeds out of lava rock can be hard on the fingers. Learn about your plants and the area that you live in. I live in a flood plain area. I use rock mulch for pathways in the gardens and I do not use wood mulch in my gardens that are in the flood plain area where it can float off into the river. I also consider the expense of using wood mulch in my gardens and replacing it yearly. I prefer to use homemade compost because it is free and better for my environment of a flood plain. I also like ground cover plants instead of mulch. If you are going to use mulch - do your homework!
The Creative Gardener