Moss and Algae In Lawns

Moss or algae in the lawn is generally caused by one or more factors. Remove moss or algae with a rake or some other tool before applying controls. The six major causes of moss or algae follow along with the controls.

• Lack of fertility. Apply 5 lbs. of ammonium sulfate per 100 sq. ft of damp moss. Do not wash the ammonium sulfate into the soil after application. Alternatively, use 5 ounces of copper sulfate (bordeaux mixture) in 4 gallons of water and spray over 1,000 sq. ft. In addition to one of the above, the lawn needs at least 2 lbs. of nitrogen per year per 1,000 sq. ft.
• Poor drainage due to clay soil. Provide good surface drainage with a one or two percent slope (or a 6" to 12 " drop per 5 linear feet). The drop should not exceed 3 to 4' per 50 linear feet. If the drainage is still poor, install drain tile 3 feet below the soil surface with a fall of 6" per 100 feet at about 20 foot intervals. A trench filled halfway with gravel or crushed rock, with a strip of typar laid over the rocks and soil on top will also work.
• Low pH factor must be raised. pH should be no lower than 6.2. To raise the pH one unit, use 100 lbs. of ground limestone for each 1,000 sq. ft of lawn. Do not apply more than 50 lbs. at one time.
• Improper watering. Do not water more than the soil is able to absorb. Water enough to replenish the entire root zone to a depth of 6-8 inches. Heavy soil may require at least 1-2 inches to wet the soil 12 inches deep and this can be done with a slow application every 8 to 10 days.
• Too much shade. To control shade, cut tree limbs to a height of 10 to 20 feet. Cut large tree limbs in the dormant season if possible. Late fall is preferred. If trees are not the cause of shade, seed with a blend of the new tall fescues and red fescues.
• Soil compaction. Compacted soil has a tendency to be too wet. It may be necessary to aerate the soil. Aerating is done with a power driver machine that usually removes cores of soil almost 1 inch across and about 3-4 inches deep. After aerating the lawn, apply Gypsum at the rate of 50 lbs. per 1,000 sq. ft. Do this twice, once in the spring and again in the fall.

To kill moss use 2 oz. powdered iron sulphate in 3 gallons of warm water, spray through a hose end sprayer. Avoid spraying sidewalks or painted surfaces as it can stain. Or use Safers "Moss Attack" for lawns or Sudbury "Moss Master".