Suitable organic mulch materials for vegetable and flower gardens should decompose within a season and should not contain undesirable quantities of viable seeds and harmful disease organisms or pests. The material must be easily applied and remain in place. It should not pack down and should be effective for at least one season. If possible the mulch should be incorporated into the soil for further decomposition at the end of the growing season.
In these gardens, mulch should be applied soon after the emergence of the crop seedlings or following plant transplant. A delay in application may be desirable if the soil has not warmed sufficiently during the spring season.
The depth of a mulch layer will be influenced by the texture of the mulch since a primary objective is to prevent the germination and growth of annual weeds and grasses. The amount used may vary from 1 inch for saw dust, peat moss, lawn clippings, compost or similar density material to 4 to 8 inches of straw, hay, corn stalks or other coarse materials.
Yard trash such as lawn clippings, leaves, pine needles, spent vegetable plants is inexpensive and valuable resources for vegetable and flower garden and landscape. Yard trash can be placed in a compost pile and used later for mulch or soil conditioning.
Leaves, twigs and other large pieces should be shredded to aid in the speed of decomposition. A lawn mower can be used to shred the leaves during the fall season. Large limbs and plants will have to be put through a shredder that can be rented at most rental companies.
The most popular mulches for landscaping are the chipped or shredded tree bark. Hardwood bark is the best mechanical mulch, since it is fibrous and will interlock. It is heavy enough to provide good moisture retention yet it allows good water and air permeability. Hardwood barks also have good antifungal and anti-insect properties. The colored mulches can add aesthetic value to any landscape.
Cedar mulch is also a shredded mulch that will not move with runoff. It has similar properties to the hardwood bark, but is limited on insect resistance. The cedar mulch comes with a pleasing aroma that many landscapers enjoy.
Pine bark is an acceptable mulch, but it lacks the interlocking abilities of hardwood mulch, and therefore it tends to wash away. It has good properties of all hardwood barks concerning insects and fungus growth.
Colored rubber chips should not be used above plant roots since moisture retention is poor and no decomposition organic materials are ever added to the soil.
Other types of mulch that gardeners may want to consider are the polyethylene film, plastics and woven fiber. Airtight sheets of plastic or polyethylene provide excellent grass and weed control but are less desirable as mulching materials because of the lack of air and water movement into the soil. A woven or porous film called landscape fabric; works best because it allows water and air to enter the soil but still prevent grasses and weeds from growing.
Rocks, stone, and pebbles make poor mulch because they absorb heat and make the area too hot for good plant growth. Bermudagrass and weeds are difficult to keep out of rock beds, resulting in a weedy mess.