Following last month’s tips for growing a green and healthy lawn, here a few tips for maintaining it.
Fertilizing may be the primary endeavor for maintaining your lawn. If used correctly fertilizer can help to improve and maintain your lawn. The reason your grass needs fertilizer is because of the stresses we put on it including the normal wear and tear of walking running and playing on it, and also the stress of cutting and removing the clippings. (If you leave the grass clippings on the lawn you can reduce your need to fertilize, provided the clippings are small enough to fall down between the blades of grass and decompose.)
Grass needs nitrogen (N), potassium (K) and phosphorus (P) and some micronutrients to grow. The type of fertilizer to use is dependent on your soil needs. Turfgrass needs nitrogen more than any of the other nutrients and Minnesota soil has an abundance of phosphorous, so there is no need to add any. In fact Minnesota law forbids the use of phosphorous fertilizers on lawns except for four conditions; the establishment of a new lawn, a soils test provides evidence of a phosphorous deficiency, commercial production of sod and application to a golf course by trained professionals.[i]
The best time to apply fertilizer to your lawn is when it is actively growing. Most of the turfgrasses we grow are cool season grasses which grow rapidly in spring and fall and then become inactive in the heat and drought of summer. Grass grows in temperatures between 55° and 75°, so the best time to fertilize is in the spring and fall. How often to fertilize depends on a variety of factors, including the species, watering, shade, the organic matter in the soil and your desire for a dense, green lawn. And remember if you leave your grass clippings on the lawn you can reduce the amount of fertilizer you apply.
Using weed and feed fertilizers may not be the best approach to weed control for your lawn. The best approach starts with good cultural practices to prevent weeds. Weeds thrive in our lawns due to a variety of environmental conditions including low nitrogen, high PH levels, compacted soil, dry areas or poor drainage and surface water (which can encourage moss and algae growth.). Correcting these condition will help reduce the weeds invading your lawn.
To eliminate the weeds already in your lawn, monitor them and use the appropriate herbicide at the appropriate times and places. Not all weeds respond to the same herbicides.
The one weed that most homeowners find most aggravating is “Creeping Charlie.” It is an aggressive, perennial plant that remains green year round, has little purple flowers in the spring and fall, and has a distinct advantage over turfgrass in the shade. Creeping Charlie has fibrous roots and above ground creeping stems called stolens. New stems grow from the joints of old stems. The best way to prevent Creeping Charlie is to grow shade tolerant grass that is dense enough that it will not find a place to take hold. As soon as it appears in your lawn you should hand pull the plants – repeatedly, removing the fibrous roots. If Creeping Charlie is invasive throughout your lawn precluding hand pulling try applying a pre-emergent herbicide containing triclopyr in the fall. This may require several applications to completely eradicate Creeping Charlie.
If you would understand more about the timing of lawn maintenance by the species of grass, a lawn care calendar is available on the University of Minnesota Extension website at extension.umn.edu.
[i] This law was enacted because the runoff of phosphorous containing fertilizer was producing an abundance of algae and other aquatic plants in our rivers, lakes and wetlands.