To understand why mowing is so important to the health of your lawn, you need to get down to lawn level and see what mowing really does.Grasses are like most plants – if you clip off the growing points, the plants branch out and become denser. If you didn’t mow at all, your lawn would look more like a prairie. You would have a bumpy surface composed of mounding or spongy grasses, separated by open spaces or weeds. When you mow each grass plants fight for every available space, and eventually creates a dense turf. But the mere act of mowing is not what makes lawn look good. Mowing height and frequency determine how healthy and attractive your lawn looks. After all, cutting a lawn is stressful for the grass.
How Cutting Affects Grasses?
Mowing Does Not Benefit Grass!
- It removes part of the leaf area which is important for photosynthesis, the process that manufactures food for growth and other life processes.
- Cut leaf tops are injured and the possibility of grass disease infection increases.
- Cutting grasses excessively low, at one time, is quite damaging. This is referred to as “Scalping “.
- Scalping clips the grass plant off at the crown, thus disrupting root growth and reserves, resulting in poor root growth.
- Cutting stimulates top growth at the expense of root growth.
How to Reduce Damage?
- Mow frequently to remove as little of the green area of each leaf as possible.
- Mowing frequently reduces shock to the plant.
- Mow at the right height and don’t cut off more than a third of the blade.
- Use mowers with sharp blades.
Turf grasses vary considerably in their tolerance to height of cut. Height of cut should be adjusted to suit physiological and morphological characteristics of various grasses. Functions of grass may determine cutting height, i.e. sports turf, greens, fairways, etc.
Never remove more than 1/3 of the leaf surface in one mowing!
- By allowing grass to grow tall the lower blades are shaded and when the tall growth is removed, the exposed lower blades are scalded by the sun.
- The shorter turf is cut, the more often it must be mowed.
- Removing too much leaf surface also reduces available nutrients during time of stress.
- Grasses that have excessive horizontal growth or stoloniferous growth, tend to require a lower cutting height.
- Height of mowing is measured on a solid surface (floor, sidewalk) to edge of the bed knife on a reel type mower, or to the cutting edge on other types of mowers.
Recommended Mowing Heights and Frequencies for Lawns and Similar Areas.
Fine ornamental lawns: 12mm, 1-2 per week, mid spring to late summer (maximum growth period) and 20mm autumn to early spring (growth slowed or stopped).
Utility lawns: 25mm, 1 per week, mid spring to late summer (maximum growth period) and 25mm autumn to early spring (growth slowed or stopped).
Parks/Landscape areas: 25mm, 1 per week, mid spring to late summer (maximum growth period) and 25mm autumn to early spring (growth slowed or stopped).
Benefits of Frequent Mowing
- Growth hormones present in the apex of plants prevent lateral bud growth and tillering – referred to as ‘apical dominance’
- By clipping grasses frequently, apical dominance is destroyed and stimulation of lateral buds and tillering is encouraged
- Grass becoming finer, sod thicker and more dense
- Cutting stimulates rhizome and sod formation
- Establish a desirable height of cut and maintain it
- Established lawns should be cut early in the spring, as soon as the grass begins to grow.
- Grass grows in cycles; quicker in the spring and autumn.
Golden Rule: Mow when needed!
Grass itself will provide criterion as to the need to adjust mowing practices:
- July/August: Clippings decrease due to heat. Reduction in mowing frequency and raising height will help grass to survive.
- In spring and autumn, grass grows quicker, producing more clippings.
- Close mowing during warm weather will weaken grasses, because the plant’s respiration rate increases and uses nutrient reserves.
- Before winter, under normal conditions, grasses should be cut at or slightly below normal height. This depends on what conditions winter normally brings.
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