Weymouth, Mass. — When the mail arrived on our desk the other day, it contained a list of mulching materials put out by Gardens for All, a national association for gardening headquartered in Burlington, Vt.
The list could not have been mor timely.
With the temperature climbing into the 90s that day and the hottest weather of the season still ahead of us, proper mulching becomes of great importance in the garden.
So, after many years of testing, Gardens for All compiled its list, along with the advantages and disadvantages of each of the materials. All are readily available to the home gardener:
Aluminum foil (WND -- will not decompose), one layer -- Increases light around plants; aphids, other insects avoid. Reusable. Can tear if handled roughly. Expensive. Artificial looking. Keeps ground very cool. Apply only after ground has warmed up.
Bark chips, 2 to 3 inches -- Attractive, good for permanent mulch. May hinder water penetration. Decomposes slowly unless composted first. Redwood decomposes slowest; may repel insects. Reusable.
Brick chips (WND), 2 to 3 inches -- Cheaper than stone mulch. Nonflammable. Not readily available; high moisture retention. No organic matter added. Decorative; made from brick overburns.
Compost, 1 to 2 inches -- Cntributes nutrients; turns quickly to humus. Needs heating period to kill of seeds, diseases; may have unpleasant odor. Plan and start ahead so compost will be ready.
Corncobs and cornstalks, 3 to 4 inches -- Readily available in most areas. Good weed control. Water doesn't penetrate well; cobs may generate heat. Add nitrogen to aid decomposition. Avoid diseased stalks, cobs. Best chopped.
Cottonseed hulls, 2 to 4 inches -- Fertilizing value similar to cottonseed meal. Very light, wind scatters. Keeps down weeds between rows. Top layer of another mulch prevents scattering.
Grass clippings, dry, 2 to 3 inches -- Improves soil by adding organic matter. Absorbent; may carry weed seeds. Mix with other materials to prevent packing; Bottom layer decomposes rapidly; add more.
Hay, 4 to 6 inches -- Legume hays (alfalfa) add nitrogen. First cut hay full of weed seeds. Poor weed control. Fewer weed seeds in second or third cuts. Fluff up during season.
Leaves, 2 to 3 inches -- Contains many trace minerals; best food for earthworms.May become soggy and pack, hindering water penetration. Chop or mix with another mulch to prevent matting.
Paper, 5 to 10 pages or 2 to 4 inches, shredded -- May add trace minerals. Decomposes readily. Newspaper or scrap paper. May pack and hinder water penetration. Scatters. Lead in colored pages; use black and white pages only. Hold edges with rocks or earth. Best shredded. Slightly alkaline.
Peanut hulls, 2 to 3 inches -- Adds nitrogen, phosphorus, and potassium; decomposes rapidly. Not readily available in North. Attractive to rodents if not completely free of peanuts.
Peat moss, 1 to 2 inches -- Clean and free of weed seeds. Improves water retention when tilled into sandy soil. Extremely absorbent; water penetration hindered; expensive. Adds little or no nutrients. Good soil conditioner to loosen heavy soils and acidic. Decomposes slowly.
Pine needles, 3 to 4 inches -- Light; usually free of weed seeds; absorbs little moisture. Does not pack; reusable. Decomposes very slowly. Add nitrogen for faste decomposition. Slightly acidic.
Polyethylene, black or clear (WND), one layer -- Retains, but absorbs no moisture. Black is effective weed control. Weeds grow under clear plastic. Rain can't get through easily. Adds no nutrients. Warms soil. Effective with tropical crops (melon or tomato, for example). Ground must be moist before applying.
Rock, crushed gravel, or marble chips (WND), 1 to 2 inches -- Relatively inexpensive; not absorbent.Water penetrates, nonflammable. Poor weed control. Adds no organic matter to soil. Should be considered permanent mulch.
Salt marsh hay, 4 to 5 inches -- Usually weed free; free in marshy areas or along coast. Long lasting. Not available to everyone. Expensive if bought. Till under at end of season. Chopping may make more attractive.
Staw, 4 to 6 inches -- Adds nutrients; lightens soil when tilled under at end of season. Can be a fire hazard. Add nitrogen to aid decomposition unless aged.
Vermiculite or perlite (WND), 1 to 2 inches -- Totally Sterile. No weed seeds. Expensive; very light; scatters. Hinders water penetration. Good for greenhouse.