Of the 150-160 grass species found in England, but only about six are used for lawns. Proprietary lawn seed mixtures consist of the merchant’s special mixes of some or all of these seeds and are sold according to the type of lawn required and, of course, price. In purchasing proprietary seed mixtures it is important to buy from a fair and knowledgeable firm. It is advantageous if the supplier states the constitution of his mixtures. Under the Seeds Regulations Act it is not compulsory for suppliers of lawn grasses to disclose the constituents of their mixtures, but many do.
A very important factor in judging a given species or variety of grass is the tolerance of cutting at any given height. This factor must be clearly understood (eg perennial ryegrass will not thrive if cut closer than 2.5cm (1 in) and disappointing results are obtained if over-severe mowing is imposed on a mixture.
Perennial ryegrass (Lolium perenne) Some varieties of perennial ryegrass have little tolerance for regular mowing at all. The varieties most suited to turf formation are those selected as late flowering, leafy, persistent type of which the Aberystwyth strain `S.23′ was the first reliable example. This variety maintains a high standard so that it continues to be popular although new Continental varieties are now available which compare very well. These include the varieties `Heraf,`Sceempter’ and ‘Melle’.
Sown alone, even the best ryegrasses seldom form a sufficiently dense sward to suppress weed invasion and none will persist when mown at 1 cm (1/2 in) or less. Perennial ryegrass is best suited to conditions of reasonably high fertility and provided that this facility is maintained, the height of cut kept at about 2.5cm (1 in) and mowing is frequent throughout the growing season, ryegrass will prove suitable for a second or third quality lawn, ie the drying ground type of lawn.
Timothy (Phleum) There are new leafy varieties of this valuable agricultural grass, the special characteristics of which are good winter color and ability to recover after wear. Unfortunately establishment from seed is rather slow, so that the grass does not compete very successfully with other grasses in a mixture, especially perennial ryegrass.
The British variety, ‘S.50’, the Swedish variety, ‘Evergreen’, and the Dutch variety, ‘King’, are very good but are all rather expensive and since Timothy is suitable only for second-class lawns (or first-quality playing fields) this is not an attractive lawn grass at the present time.
Rough-stalked meadow grass (Poa trivialis) A fairly dwarf grass, this is sometimes employed in the cheaper, second-class lawn mixtures. There are no good new varieties of this.
Smooth-stalked meadow grass (Poa pratensis) This is receiving the attention of the breeders and there are some very good varieties, particularly the Dutch one known as ‘Prato’ which is likely to appear in quite good lawn seed mixtures. Slow in establishing, smooth-stalked meadow grass ultimately forms a very dense, durable, drought-resistant sward if not mown too closely and the vigorous rhizome development allows good recovery after wear. Unfortunately, smooth-stalked meadow grass does not thrive under close mowing and in fact is best kept at 2-2.5cm (3/4 1 in) in height so that its use for fine lawns is rather limited.
It is quite a good bottom grass for second-class; quality lawn mixtures but again there ‘are no new selected varieties available as yet. This grass is tolerant of low fertility and has good winter color and hard-wearing qualities. Selected varieties might, therefore, prove extremely useful.
Creep’ing red fescue (Festuca rubra var. rubra) This is suitable for inclusion in good lawn mixtures but does not stand very close mowing and so is not suitable for really high class lawns. There are selected varieties of this grass available, in cluding ‘S.59’, a fine-leaved winter ggreen selection, which forms an excellent ‘turf either alone or in mixtures. There are also new Continental varieties of creeping red fescue which are good, eg `Oasis’ and ‘Brabantia’.
Chewings’ fescue (Festuca rubra sub. spp. commutata) is the fescue which (usually mixed with browntop bent) is used to form best quality fine turf in Britain and which is also included in less fine mixtures because of its excellent turf-forming characteristics. Very good quality seed is on the market these days from America (no longer from New Zealand) and there are new selected varieties from Holland, namely ‘Highlight’ and ‘Brabantia’, which are very good indeed. One of the main disadvantages of all Chewings’ fescue is, of course, that their winter color is poor. Bent grass (Agrostis species) The fine bent grass used for forming fine turf (usually mixed with Chewings’ fescue) is normally Agrostis tenuis (browntop bent) and the main source of supply is America since New Zealand has more or less gone out of this market. The brown-top forms a very fine, dense turf, tolerant of close mowing, while as a constituent of all turf mixtures it is a very valuable bottom grass.
It is, perhaps, interesting that in the parts of the United States where weather conditions are comparable with those in Britain, browntop bent (Agrostis tenuis) is not as popular as creeping bent (Agrostis stolonifera) of which there are many named varieties, almost all established vegetatively rather than from seed. There is, however, at least one reasonably satisfactory variety of creeping bent which in America is established from seed, this being known as ‘Penn-cross’.
Other grasses From time to time other fine-leaved grasses such as hard fescue (Festuca longifolia) are used in lawn seed mixtures but their value is believed to be rather limited except possibly in relation to price.
A demand for grass seed mixtures suitable for shade conditions continues to exist despite the fact that there are really no suitable grasses for growing fine lawns under shade conditions.
Generally speaking the grasses growing on the non-shaded area of a lawn are fairly suitable for growing under the shade if the height of cut is increased. There are no grasses which both tolerate mowing and really thrive under shade conditions.