MOWING The height of cut and frequency of mowing are important factors in lawn maintenance. Too close mowing weakens the turf and leaves it susceptible to moss and low-growing weeds. Coarser grasses become more dominant where it is allowed to grow too long and is mown infrequently. Frequency of mowing must be related to differing seasonal growth rates. During late spring to early autumn when growth is vigorous mow the finest ornamental lawns every two to three days; average lawns every three to five days; other general-purpose and utility areas every seven days. As vigour declines in the autumn reduce the frequency. From October until March there will be little need for the mower, except in very mild winters or in sheltered coastal areas where an occasional light topping may be necessary. The height of cut is determined by the time of year and the kind of turf being mown. During the period of vigorous growth mow the finest ornamental lawns to between J to |in (0.5 to ion), average lawns to iin(icm) and general-purpose or utility turf to about iin(2.5cm). Turf is weakened if regularly mown to below nsin(o.46cm) and coarser grasses begin to dominate finer grasses where it is not kept to i|in(4cm) or less. From autumn to early spring when growth is slow, raise the height of cut by jin(o.5cm). Also raise slightly during periods of drought when irrigation is not available. MOWINGS Most gardeners remove the mowings from ornamental lawns as there are usually few periods when they will rapidly shrivel and disappear from the surface. If not collected, they are likely to remain to spoil the appearance of the lawn as they slowly decay. Often the mowings will contain viable weed seeds, such as annual meadow grass, or the severed stems of white clover or speedwell which, if scattered, will take root in moist conditions. Mowing is certainly less arduous without the weight of a filling grassbox and the necessity for frequent trips to the compost heap. Also, nutrients are returned to the soil if mowings are allowed to "fly" and they act as a mulch in periods of drought. Obviously, therefore, there are occasions when it is advantageous to leave the mowings uncollected, but in most instances it is more advantageous to remove them. MOWERS When buying a mower ensure that it is of a suitable type and size to deal easily and satisfactorily with the turf to be cut. All lawn mowers are based on one of two cutting principles. Cylinder mowers have several moving blades arranged in a cylinder and cut by trapping the grass between a fixed blade and each successive moving blade. Rotary mowers have a cutting device suspended and rotating beneath a protective canopy, cutting the grass by the high-speed impact of a sharp-edged bar or with blades attached to a rapidly revolving disc. Modern rotary mowers give a neat finish and will cut grass of any height but the scissors-action of the cylinder mower will give the finest finish to a lawn.