Bowling Green Performance Standards (C)

9) Thatch depth: This is undesirable and should be reduced to a very small amount, although a little depth of thatch, of maybe 3mm to 5mm, is desirable in contributing to sward resilience. For a very good standard of bowling green the depth might not exceed 6mm; whilst for a general standard of bowling the aim should be for no more than about 12mm. Where thatch is 25mm or greater, then this will be having a significantly negative impact on the surface and playing experience, although at certain times of the year when it is very dry this will not be as noticeable and visiting clubs may think that on the short time of their visit the green was actually good, but for a lot of the season this would not, typically, be the case. The depth of thatch will help inform on the degree and frequency of scarification and verticutting needed, as well as whether any specific types of aeration work might be needed, for example, hollow-tining.
10) Weed content: This can be a general indicator of all types of weed or one that has sub-categories of large-leaved weeds, small-leaved weeds, moss and algae. A small amount of weed infestation shouldn’t be a particular issue for most greens. However, deciding on the parameters where action needs to be taken will relate to the extent of ‘pristineness’ wanted from a green. High weed contents, especially where they are concentrated in clusters can impact on bowl roll and delivery. For high quality greens a maximum small-leaved weed content of no more than 1% might be desired, ranging to no more than 10%, which might be acceptable for general quality greens. Large-leaved weeds would not be desired on any green and once noticed they would typically be hand weeded from the green. In practice there might be a juvenile stage of some large leaved weeds, so in essence these would appear as small leaved weeds. Algae and lichen are not organisms that would be normally encountered on a bowling green, so this parameter would typically be zero, whilst for moss this can be a particular problem on some greens, especially those which are enclosed by surrounding trees and hedges. High class surfaces might aim for a maximum of no more than 0.5% moss content, whilst general quality greens might be no more than 10%, but local conditions for some greens might relax the criteria during the autumn and winter months to maybe 15% as a maximum.
11) Earthworm surface casting: Surface casts can affect the roll of a bowl and reduce the quality of the sward content. However, during the playing season, the amount of surface casting should be minimal as drier surface conditions will prevent or significantly reduce the activity of earthworms in the surface layer. A small number of casts isn’t going to be a problem, but as the density of cast increase so will the problems and challenges in overcoming the negative effects of these. In practice, the main periods for surface activity are out of season when it is cooler and when the soil is moist to wet. It is during this period that surface casts can smear when switched or brushed and start to smother some of the sward and provide a seed bed for weed species and annual meadow grass in particular. On general quality greens a maximum coverage of 5% out of season might start to create issues with maintenance work, although with most greens being on a sandy soil this should not cause major problems to a greenkeeper, rather more a nuisance of constantly having to disturb the casts and redistribute them. For higher quality greens a figure of no more than 2% might be more appropriate. The beneficial effects of earthworms within a soil, especially regards improved soil aeration and breakdown of organic matter should not be overlooked.