We are all seduced by images of magnificent stately home lawns, and dream of lazing our days away on the lush grass with a glass of our favourite tipple in hand. However for many of us, the reality is that our lawns have come into spring looking tired, with weak grass and dominated by moss. Help is on hand however as Steve Gingell, agronomy operations manager, gives us a few tips to help rejuvenate our turf.
A lawn’s best chance
In order to get the best out of a lawn the grass needs to be given the best chance to compete against other invaders such as moss and weeds. To achieve this, plant health must be maximised, particularly with nitrogen (the element that promotes growth and greenness) and the roots need to be as deep as possible.
The moss we commonly see at this time of year is an opportunist, it thrives in the lower light conditions of winter and fills any gaps. Another factor is saturated poor draining soil, which needs soil improvement and regular top dressing. But that’s for another article.
Traditionally we would try to treat the moss with iron sulphate, applied either as lawnsand or within a fertiliser mix, to blacken and kill it (well at least desiccate it a bit) before severely scarifying and ripping out the moss, along with much of the grass. In my experience though, the moss grows back if the health of the grass over the whole year is forgotten.
So, what to do? Well the best defence is to use a spring feed with a medium strength fertiliser (with a formulation of 7-14% nitrogen on the package) probably containing some form of iron. This promotes grass growth and weakens any moss.
However, in very sickly lawns this will quickly fade, and the grass will not be able to compete with the moss to give a great lawn over the year. So, for best results, apply the feed two to four times a year on sandy soils and twice a year on clays.
It is vital to accurately apply the fertiliser with a spreader as overlap and misses will be very visible. If you are applying a multi-purpose feed, moss and weed kill fertiliser, accuracy is particularly important as scorch marks can occur on the overlaps.
Larger rosette weeds are often best dug out. Also make sure safety recommendations are followed on
Raking and scarifying
After the feed, a light rake or scarify will lift some of the moss out. In the higher growth conditions of the spring the grass will recover more quickly than undertaking this work in the autumn. In the autumn there’s a risk of opening up the grass and the low growth rates allow moss and weeds to easily invade.
While the weather conditions are good, raking can be followed up by overseeding with ryegrasses for a
utility lawn, or fine turf seed mixes for a luxury lawn – apply around one handful per square metre.
Ideally the seed needs to be in soil contact and top dressed with a sandy loam soil or a quality free-flowing sand (not building sand) applied at a rate of up to 10kg/m2 to cover the seed and improve
the surface. The dressing should follow aeration and be brushed in.
Grass roots develop actively in the spring and need space to explore in a well-structured soil (one with lots of micropore space). However, after winter many lawns will be compact and rooting could be compromised. This was apparent in the wet, cold spring of 2018 where rooting was shallow and then baked in the hot summer.
On a small lawn, forking vertically to full tine depth and then lifting straight out creating holes in a square pattern is easiest and good exercise! On larger areas use a mechanical aerator. Ideally this should be done at least twice over the spring. Roots will beneficially follow down a tine hole and explore the full
Over winter the grass height will have increased if you’ve not been mowing frequently. This needs to be gradually reduced in stages to the summer height, leaving a couple of cuts between each lowering.
There is no set best height, but a nice lawn cut between 25-30mm gives the best combination of health and aesthetics. Ideally no more than 30% of the grass leaf height should be removed at each cut, so as growth increases into the spring then the frequency of mowing will have to increase.
Finally make sure mower blades are sharp to give a clean cut.
Steve Gingell is STRI’s agronomy operations manager, and has a wealth of experience advising to the Commonwealth War Graves Commission, English Heritage, the Royal Household and as a horticulture lecturer. For more information on STRI’s commerical grounds and estates services contact firstname.lastname@example.org or call 01274 565131.