Golf Greens Mowing Height of Cut

Greens are typically mown at a height from 4mm – 7mm during the main growing season and between 5mm – 9mm outside of the main growing season. A typical height of cut during the main growing season for the majority of clubs will be 4.5mm-5mm (which is the traditional 3/16", actually 4.76mm), whilst outside it can be up to 8mm, although some courses will continue to maintain it at 5mm over the winter period. Low heights of cut, especially during slowing growth periods into the autumn, limits the grass plants ability to build food reserves (carbohydrates) over that period for use during the winter and early spring.

For tournament play a height of cut of 1/8" (3.2mm) to 5/32" (4mm) is sometimes applied, however, this should be carried out in a gradual phased way, over one to two weeks, leading up to the tournament so the grass plant isn’t suddenly shocked with the decrease in cutting height and which can result in a noticeable reduction in sward quality and questions asked of the greenkeeping expertise.

Traditional imperial to modern metric figures, with practical day-to-day figure in brackets:
• 1/8" = 3.18mm (3mm)
• 5/32" = 3.97mm (4mm)
• 3/16" = 4.76mm (5mm)
• 7/32" = 5.56mm (5.5mm)
• 1/4" = 6.35mm (6.5mm)
• 9/32" = 7.14mm (7mm)
• 5/16" = 7.93mm (8mm)

Greens with contours and slopes will be more prone to scalping where very low heights of cut are being used, so it is important for a greenkeeper to know the lie of their greens to a high degree to avoid this occurring. Thatch depth and the moisture content of the thatch at the time of mowing can have a significant impact on the resulting cut height as a mower will sink in slightly to a softer surface. Even a small sinkage of 1 or 2mm can have a significantly detrimental impact on the quality of the sward, especially if the aim was for a 4.5mm effective cut height, but the resulting cut height was actually 2.5mm.

Excessively short mowing may provide a relatively fast green speed, but this will typically be at the expense of increased moss and thin areas, grass areas which are more prone to heat stress and thatch production, reduced root growth, reduced resilience and with increased maintenance and pesticide inputs. All of this is aiming to produce a suitable sward quality which is always in tension with overengineered agronomic practices and is not a situation which can be claimed as being in sympathy with sustainable practices.

Some golf greens in the UK are maintained at exceeding low heights of cut, for example, 2.5mm and they produce fast and good playing surfaces (in contrast to fast yet poor surfaces which is arguably the more common result from mowing at such heights). These heights of cut are certainly not the norm, but good surfaces can be produced and sustained where highly skilled and knowledgeable greenkeepers, with appropriate resources, are employed. The difference between success and major problems is much narrower (and more of a gamble) when compared with more ‘traditional’ heights of cut, so where success is achieved this demonstrates the exceptional abilities of the dedicated greenkeeper team. For most situations the very low cutting heights would not be recommended and elite courses, such as St Andrews will routinely mow at 4.5mm during the main growing season, reducing to 4mm for some events up to about 10-dyas before resorting back to normal mowing heights. Where major tournaments are held, for example the Open, then this might be reduced to 3.5mm for a short period, but where possible mowing heights would not be that low. (Moir, G, (2022), ‘St Andrews. The Greenkeeper’s Tale’, pp202)

Ideally, the aim should be to mow as high as practically possible to help encourage as deeper rooting grass as possible. During dry weather it is desirable to raise the height of cut to at least 6mm. If speed is a major concern, then it is better to double mow than to actually lower the height of cut as this just stores up problems for later on.

Great golf has been played in the past and will continue to be played. The desire for some greenkeepers to vocally reinforce how short they can mow their greens has in some ways become a ‘badge of honour’, in a similar way that green coloured greens must surely be good, when often this is not the case. It is the quality of the sward, in particular the quantity of finer grasses, with a drier firmer surface, with green colour being an element of good quality but not to the extent many make out, along with capable greenkeepers and competent or better golfers that makes for great greens.

The surrounds to a green will typically be mown slightly higher than the green, at 6.5mm to 8mm, whilst the apron might be anything from the same height as the green to that of the surround.