Lawn Care

Phosphorus as a lawn fertilizer element has made the news lately as being a major cause of water quality issues in our lakes and streams. Excess phosphorus, from phosphates in lawn fertilizers causes algae growth and reduces water quality, especially in standing bodies of water such as lakes. If any of you are as old as I am, you may remember when phosphorus was removed from laundry detergents for this very same reason. It helped whiten fabrics, and my mom was very worried about getting Fred’s shirts their whitest after it was banned. But somehow we survived that crisis. Some cities and states have already banned phosphates in lawn fertilizer. Minnesota banned phosphates in 2005 and Maine in 2008. Here in Chicagoland, Antioch and Third Lake, in northern Illinois recently banned it.


So, what is phosphorus and why is it in fertilizer? When you buy fertilizer there are usually three numbers on the box or bag that describe the available amounts of nitrogen, phosphorus and potassium. Nitrogen is responsible for green growth in plants. It is what makes the grass green up in the spring. Potassium helps with general plant health, including tolerating stresses such as heat, cold and disease resistance. Phosphorus, in the form of phosphates, stimulates root growth, increases stem and stalk strength and improves flower formation. This is why we always recommend high phosphate starter or transplant fertilizers when planting new annuals, perennials, shrubs and trees. It is generally not necessary in lawn fertilizers, unless soil testing shows your soil to be phosphorus deficient and then only when seeding or laying sod.

Americans love their lawns and strive for the greenest lawn on the block. Proper lawn care will help your lawn look its best and reduce your use of fertilizers and herbicides (weed killers). The following steps will help your lawn look its best:

1. Aerate: The soil beneath most lawns becomes compacted over time reducing the amount of oxygen available to the roots. Aerating even once a year will help this. After aerating you can top dress with compost to add organic matter to the soil. This will help reduce the compaction further, increase drainage and increase the water holding ability of the soil.

2. Watering: Most lawns (and plants) need an inch of water a week. It is best to water infrequently but deeply to encourage roots to grow deep. This will help during periods of drought.

3. Fertilizing: Fertilize in the early spring and fall, when the grass is actively growing. Don’t fertilize during the hot summer months. Sweep up any fertilizer that gets on the drive or sidewalk.

4. Mowing: Cut the grass to a height of between 2-3 inches and only remove one-third of the growth at a time. This may mean cutting the lawn twice a week instead of weekly. Leave the grass clippings on the lawn. They will decompose over time and add organic matter back into the soil. Keeping the grass cut high should also reduce weeds as the grass will shade the seeds and keep them from germinating. A thick healthy lawn is better able to crowd out any weeds that are growing.