The ideal time to apply mulch in flower and vegetable gardens is late spring after the soil has warmed up. Replenishing beds where existing mulch has thinned is the step after that.
This can be the best way to protect plants from summer's heat, drought and weeds. Mulching also can reduce soil erosion, compaction and crusting. Unless you know what you’re doing, though, it can create as many problems as it solves.
Three hard-and-fast rules apply for both inorganic and organic mulches said:
1. No mulch may touch plants’ crown, stem or trunk. Contact fosters diseases and provides insect cover. Over time, it can make plants think their soil level has changed. The size of the bare-dirt “doughnut hole” should relate to plant size – an inch or so encircling tomato vines and a foot left uncovered around mature trees.
2. No mulch should touch any building-related wood, from house siding to door frames. Mulch within 6 inches of foundations should be less than 2 inches deep. Many mulches aren’t desirable insect food. Whether lava rocks or cedar chips, however, mulches look like moisture-retaining cover to termites.
3. Mulch that’s too deep can be as counter-productive as a layer that’s too shallow. The most effective depth depends on the material. In general, thin, fine materials (grass clippings, peat moss) are best at 1inch deep or less. Big cedar bark chunks need to be 3 to 5 inches deep. The in-between sizes can be 2 to 4 inches deep.
Except for these rules, no “best” advice for choosing and using mulch exists. Each mulch material has pros and cons. Mulches vary widely in color, texture, overall appearance, durability and cost.
But, for help in sorting through the factors and facts, homeowners can visit their county or district Extension office or look online for an Extension Master Gardener assessment at www.johnson.ksu.edu/DesktopModules/ViewDocument.aspx?DocumentID=6883.