What is it?
This is the removal of leaf growth from the grass plant by means of a mower, usually cylinder or rotary, but also including flail or reciprocating knife type mowers. The latter two types of mowers are for rough areas of grass and do not really produce a quality cut, but tidy up the area by producing a mown area of uniform length.
What does it do?
By mowing at optimum heights for the different turfgrass species, the mowing operation will encourage both leaf and root development, resulting in both an improved density of the sward and ability to withstand wear. Depending on how the mowing operation is carried out (see below), it can affect the growth habit of the grass plant and also the botanical composition of the sward.
Mowing is the maintenance operation which has the most influence on the production of a good sward and typically some 50%, or so, of all maintenance time spent on sports turf areas is undertaken by the mowing operation.
What influences the quality of the sward ?
There are 6 main factors that have an impact on the level of quality of any grass sward.
- The height of cut used;
- How frequent the grass is mown;
- Whether the mown clippings are removed or left on the sward;
- The direction that mowing takes place;
- How sharp the cut is;
- How even the cut is.
Height of cut
This has a very significant influence on the type of surface that is required and has to be adjusted to ensure the desired grasses are cut within a range of cutting heights that are suitable for optimum growth.
The height of cut that is set on the machine may produce a slightly different height of cut on the grass sward, depending upon the firmness of the turf and the depth of thatch present.
The only mower realistically affected by this is the cylinder mower which is used for fine turf areas. This is because a few millimetres difference at the heights used for fine turf areas can be the difference between a well mown, attractive sward and one that is shaved and patchy looking.
Shaving of the turf should be avoided as this will weaken the desirable turf grasses and at the same time encourage the development and spread of undesirable grass and weed species. The mowing of fine turf below an effective cutting height of 5mm (3/16") should not be carried out on a regular basis, whilst perennial ryegrass dominated turf is generally not mown below 25mm, although there are now a number of dwarf cultivars which survive mowing at less than this height of cut.
On fine sports turf areas occasional mowing down to 3mm is sometimes carried out for short spells, for example to accommodate special tournaments. However, greens must be very smooth, even and firm to allow mowing to such heights, with the aim of this short height of cut being to increase the speed of the green in the short term. If shaving of the grass is carried out for any length of time, this will lead to a deterioration in long term playing quality whilst increasing the frequency of mowing leads to an increase in the playing speed of golf and bowling greens and is more desirable than shaving the turf.
It should be remembered that turf is put under a lot of stress when mown very closely and the desirable turf grasses will not survive for long if constantly mown below their optimum height of cut and their place will be taken by undesirable annual meadow grass and weeds.
Typical heights of cut (given in mm) for different turf areas
| Area | Main playing season | Main growing season ~(Apr-Sept) |
Outside of the main growing season ~(Oct-Mar) |
| Golf green | All year | 5 | 8 |
| Golf tee | All year | 8 | 12 |
| Golf fairway | All year | 12 | 18 |
| Golf semi-rough | All year | 40 | 75 |
| Bowling green - flat rink | May - Sept | 5 | 12 |
| Croquet lawn | May - Sept | 5 | 12 |
| Tennis court | May - Sept | 6 | 12 |
| Ornamental lawn - very fine | N/A | 6 | 10 |
| Ornamental lawn - fine | N/A | 8 | 12 |
| Amenity lawn - fine | N/A | 12 | 18 |
| Amenity lawn - general | N/A | 25 | 50 |
| Cricket table | May - Sept | 18 | 25 |
| Cricket wicket | May - Sept | 2 | 25 |
| Soccer pitch | Aug - May | 35 | 25 |
| Rugby pitch - League | Feb - Sept | 35 | 50 |
| Rugby pitch - Union | Sept - May | 35 | 50 |
| Athletic running track | May - Aug | 18 | 35 |
The exact height of cut to use will need to take into account the standard of the area concerned as well as the prevailing weather conditions.
A good example can be local authority football pitches, which can typically be cut between 25 and 50mm depending upon the desired standards. The figures in the above table can therefore only be used as a general guide: Managers of individual turf areas will know the best height for their particular facility.
In periods of hot, droughty weather, raising the height of cut helps to reduce stress on the grass plant and can improve its ability to withstand wear. From early autumn to early spring it is also good practice to ensure the grass is not cut too close as the sward may struggle to recover adequately from very cold spells.
Wherever possible, it is more beneficial to let the grass grow a little longer than shorter, as some more can always be taken off, yet it's very difficult to put it back on!
Frequency of mowing
No more than about 30-40% of the leaf height should be removed on each mowing occasion, otherwise a rapid weakening and thinning of the sward will occur. Perennial ryegrass is slightly more forgiving at this than other grasses and it may be possible to remove up to 50% of the leaf height on occasions without major detriment to the sward.
By removing excessive amounts of green leaf (photosynthetic tissue), the carbohydrate food reserves in the roots will be used to encourage new leaf growth. This, however, will have a detrimental impact on the maintenance of a developed root system, as the carbohydrate removal will result in a reduction of root growth.
The more frequently a sward is mown, especially a fine turf one, the less clippings are produced and this results in less nutrients being removed from the soil.
Removal / return of clippings
Whilst clippings are generally not collected and are 'let fly' on general amenity lawns and large turf areas, such as football pitches, this is not the case for fine turf areas, such as golf or bowling greens or ornamental lawns, which require clippings to be removed.
Returning clippings can aid in recycling soil nutrients, but it can also encourage the development of weeds, worms and disease, as well as indirectly encouraging the build up of a thatch layer. In addition, this can be a way of helping the spread of annual meadow grass.
Clippings are, however, sometimes returned to fine turf areas during a summer drought to assist in protecting the basal crown of the grass plant and reduce the effects of the drought. If clippings are returned, then any grass clumps should be dispersed to prevent any smothering of the grass.
Direction of mowing
It is important to vary the direction of mowing to produce a more upright growing grass, which in turn assists in providing a surface that is uniform and relatively fast. Constantly mowing in the same direction will produce a washboard type effect on the turf, resulting in an uneven, bumpy surface.
Cleanness of cut
When using a cylinder mower it is important to ensure that a sharp cut is produced as this will eliminate bruising, jagged edges and chewing - all of which weaken the grass plant, making it more susceptible to disease.
Rotary mowers cut by impact and produce results which are adequate for swards dominated by perennial ryegrass, but not those which contain the finer grasses as this will weaken them considerably, leading to the area being colonised by undesirable grasses and weeds.
Evenness of cut
To prevent scalping of the sward, the mower must be adjusted to ensure the blades are set evenly across the width of the mower. This will also help to prevent any 'ridging' of the grass if the edges of the mower cut at different heights.
Ribbing can occur where the cylinder mower has been set incorrectly with either the cutting height being too short for the grass or where the bottom blade is too tight against the cylinder.
Another factor is that the cylinder speed represented by the number of cuts per unit length, typically per linear metre, is not high enough.