So, we are reflecting on the need to mow bowling greens to the traditional height of 5mm (See Reflecting on traditional practice (1)). The context here is that we want a bowling green to provide a suitable level of playing satisfaction but within limited financial resources and reducing memberships. This is not considering greens which have large memberships and more available monies.
What is the evidence?
We don’t really want a particularly slow green, i.e. one which is less than 10 seconds otherwise it is going to be very heavy and difficult to have a more elegant controlled game.
We must not get too hung up on speed though: World Bowls give performance standards for a bowling green (focussing on synthetics though) as between 10 and 18 seconds; so whilst 10 seconds is at the lower end it is still an acceptable speed.
10 seconds has been identified as an acceptable minimum speed, with 12 seconds being a preferred minimum (Perris, J. (2008) ‘All About Bowls: The history, construction & maintenance of bowling greens’, 3rd Edn, STRI, p211)
Do we want a speed which we can’t afford to maintain and ultimately creates a poor surface, or do we want a speed where we can have a relatively decent and enjoyable game of bowls on an acceptable surface which we can afford to maintain?
Green speed is related to the height of the grass, but there are other factors which affect the speed. Unfortunately there is a strong focus on the height and limited attention to the other factors.
For example, the type of grass which is present can affect the distance and speed of a green, A fine fescue or bentgrass species can add an additional second to the speed of a green, when compared with an (undesirable) annual meadow grass green. So from being generally slow to slightly acceptable, the speed could increase to slightly acceptable to satisfactory. (Perris, J. (2008) ‘All About Bowls: The history, construction & maintenance of bowling greens’, 3rd Edn, STRI, pp. 205 & 216)
If we look at desirable grass species only and consider grass height data we can see that the average speed gain for cutting from 8mm to 5mm is 0.6 seconds (Just 10.8 seconds, compared with just over 11.4 seconds for the faster and shorter height of cut – this is just an average and a generalisation but it illustrates the point of questioning the real gains from cutting short on a regular basis).
The data ranged from:
- 10.2 to 11.3 seconds for the 8mm cut green;
- 10.3 to 11.4 seconds for the 6mm cut green; and
- 10.7 to 11.9 seconds for the 5mm cut green.
How much of an impact this really has to the practical bowler is dubious at best; just think about it – half a second gained.
Increasing the height of cut from 5mm to 8mm for most occasions would, however, have a significantly positive impact on the grass plant, for example:
- 60% extra leaf area to capture energy from the sun and to help improve root growth and grass development;
- A more competitive situation for the desirable grasses, especially fescues, reducing the capability of annual meadow grass.
- Reduced fungicide applications, in principle, as the grass plant will be more stress free (from being mown too short all the time).
- Ability to withstand wear that much better.
This poses a couple of questions (at least)
- What would the speed be if we allowed the grass to grow slightly longer (say 11 or 12mm) before cutting it at a set height of 8mm?
- What impact, though, will this have on the required mowing frequency?
We know that grass needs to be mown regularly to maintain a relatively dense sward, plus it grows at varying rates from March – November, slowing to dormancy in areas from December to February, but still requiring the occasional topping.
Clearly we need to mow the green, but what frequency can we typically ‘get away with’ to ensure we can still play a satisfactory game of bowls on the green with limited membership and income (and I suppose also volunteer, or other inputs)?
We don’t want a fluffy green which affects the roll of the bowl, so what height can we let it grow to until we then need to mow it?
Each grass species will grow at different rates, and there are many inter-connected environmental factors which also affect growth rate: temperature, available moisture, sunlight, nutrient availability, age of grass plant, whether it has recently been ‘stressed’ by a mechanical operation … So giving an actual height growth is quite problematic; but we do want something to work on as a principle for our considerations.
We also need to consider how much growth can be removed each cut without being especially detrimental to the grass plant – this is typically no more than 33% (to 40%) of the leaf , so that’s a helpful point we need to consider.
One reported experiment (Shildrick, J.P. 1986, ‘Mowing regimes and turfgrass regrowth’ in The Journal of the Sports Turf Research Institute, Vol. 62 pp36-49, ), for turf mown at 12.5mm to 50mm saw the finer grasses grow an average of 2.8mm to 3.4mm per day over the whole season, although figures for the trials with lower heights of cut saw an average of 1.6 to 1.9mm per day. We mustn’t forget that this does relate to turf allowed to grow in a trial to 25mm, which is significantly higher than for a bowling green. At least it provides us with a general guide.
I couldn’t find any research for bowling green speed on greens cut at 11 or 12mm, but if we try and make a guess from the data we have, let us say there is a further reduction in speed from 8mm average of 10.8 seconds to between 10 and 9 seconds, so we are into the area of a slow green, which we don’t really want, so will need to trial and error in practice to see what we can get away with.
If we say 2mm growth per day and have a cut height of 7mm then we could cut Monday (7mm) – ideal for some good games that need playing; grows to 9mm for Tuesday (speed = OK, to slowing over the day) – plan for casual, general games that day; cut Wednesday (back to 7mm); same thing – cut Friday, cut Saturday. So 4 cuts per week, at times this could easily be 3 cuts, but we would limit the maximum to 4 cuts, except for tournaments, but there wouldn’t be too many of those at the type of club we are considering for this change of mowing practice.
If lots of greens are cut 4 (minimum) to 7 times (maximum) per week, saving one cut may only be a small saving, but the significant benefit is that considerable thought is being given to making the most of the grass surface by making the grass as competitive and as hard wearing as possible, reducing the need for other (often excessive) material inputs of fungicide, water, and fertiliser in particular. Given good greenkeeping working practices you will also see an improvement in the overall quality of the bowling green.
To sum up: For many clubs and greens, give serious consideration as to what is fit for purpose for your situation. Trying to keep up with others may not be in the best interests of your club, or green. In fact, a systematic and logical (and genuinely well-informed, in contrast to well-intentioned) approach to greenkeeping can save considerable time and money.
Chris Gray, December 20, 2016