Myth.

Contrary to the advice given in many gardening magazines and TV programmes, the grass does not stop growing during Winter in our climate. Any mild spell sees grass growing, albeit much more slowly than at peak times, and a lawn that goes into Winter well fed and hardened off comes out of it in a different class from one that was simply abandoned in October.

I am Duncan Gray, and I spent my working life as a greenkeeper. The advice below is what I do on my own turf every autumn, and it applies just as well to a back garden lawn as to a bowling green.

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Jump to a section:

• Why autumn feeding matters
• What to look for on the bag: the analysis I buy
• Autumn fertilisers I would use
• Winter: iron, not nitrogen
• Making your own lawn sand
• Coming out of winter
• If you look after a bowling green

The Importance of Autumn

One of the main secrets of a good lawn is to ensure the grass is healthy going into Winter, and this is where it is essential to feed in Autumn with a fertiliser that will provide the grass with the nutrients it requires to survive the cold frosty days, the heavy rain, or lots of snow cover. The autumn fertiliser should be applied around late September to early October, while the soil is still warm enough for the grass to take it up.

The best type of Autumn fertiliser is one that has a low Nitrogen content, as the last thing we need to do is to produce a soft lush growth which would be prone to damage by the elements, and also increases the incidence of disease, mainly Fusarium, which is rife in Autumn and can cause a lot of turf damage.

On the other hand, Potassium should be applied at a high rate, as it hardens the grass thereby helping to protect against weather problems and disease.

The other ingredient in the Autumn fertiliser should be Iron, both for the fact it also hardens the grass against the elements and disease, but is also a very effective moss killer.

What to Look for on the Bag

The ideal Autumn fertiliser has a low Nitrogen content of around three per cent, no Phosphate at all, and a high Potassium content of anywhere between twelve and twenty per cent, with magnesium, iron and seaweed added. All fertilisers show the analysis on the bag, so look for something close to the following: 3.0.12 plus magnesium, iron and seaweed. The three numbers are always in the same order, Nitrogen, Phosphate, Potassium, and the additives are listed separately. The front of the bag will usually just say “low nitrogen, high potassium with micronutrients”, which is the same thing in words. The zero figure relates to Phosphate, which is not necessary in grass fertiliser other than in the initial establishment stage. A little phosphate in an autumn feed does no harm, but you are paying for something the grass will not use. Some products carry all three of the additives and some only two; the more of them in the bag the better, and the iron is the one I would not go without.

Two things to watch for. First, “autumn” on the front of the bag means nothing on its own: I have seen so-called autumn feeds with more nitrogen in them than my summer fertiliser. Turn the bag over and read the analysis. Second, some products list the iron as “moss killer” or “ferrous sulphate” without giving a percentage. If they will not tell you how much iron is in it, assume it is not much.

There is a huge variety of different fertilisers from different suppliers, a lot of them very good, a lot promising all sorts of myth and magic, but if you follow my advice you will get good results without paying through the nose for unnecessary ingredients.

Autumn Fertilisers I Would Use

The nearest thing to that analysis that is easy to get hold of is Elixir Gardens Complete Winter Lawn, 4.3.8 with 4% iron. It carries a little more nitrogen and a little less potassium than I would choose, and a touch of phosphate you do not need, but the balance is right, it has the iron, and it comes in bag sizes from a small lawn up to a bowling green.

If you would rather pick something up at the garden centre, Miracle-Gro EverGreen Autumn Lawn Care is the one most of them stock. It carries more nitrogen and phosphate than I would choose, but it has iron in it, it is widely available, and on an ordinary domestic lawn it will do the job. Apply either at the rate on the bag, with a spreader rather than by hand, and water it in if no rain is forecast within a day or two.

Whichever feed you choose, I would put a dressing of seaweed meal on at the same time, at around fifty grams per square metre. It is a soil conditioner rather than a fertiliser, it feeds the life in the soil over the Winter, and I have used it on every green I have ever looked after. There is more on why in my article on seaweed as a lawn and garden fertiliser.

Winter Essentials: Iron, Not Nitrogen

Winter fertiliser is more about keeping the grass healthy, and moss under control, than about making grass grow. So for that the Nitrogen has to be very low, and the Iron content high.

Lawn sand has always been the default lawn tonic and moss killer from many suppliers in Winter, but many suppliers skimp very badly on the Iron content, meaning the contents look good value, but the low Iron content, mostly no more than two or three per cent, means that to get any real effect the dosage has to be high, which in actual fact means the Nitrogen level will be far too high.

Applying a lawn sand at only two per cent Iron will have very little effect on Moss, and will not help grass much either, so I always use a lawn sand that contains around two to three per cent Nitrogen, with at least six per cent Iron. This mix will read on the label as 2.0.0 + 6% Fe (iron). I would advocate putting iron on every four to six weeks from mid-November through to late February, weather permitting. Heavy frost, a very wet spell or high wind will all stop you getting an application on, so some winters you will only manage two, but aim for at least three.

The honest position is that lawn sand with that much iron in it is getting hard to buy at all. Sulphate of iron was a by-product of the steel industry and the supply has declined along with it. Westland Lawn Sand is the ready mix most garden centres still carry and it is perfectly usable, but check the iron figure on the bag before you buy and be prepared to go over twice. What I use now is dissolved iron: still sulphate of iron, made a different way, and put on in water rather than in sand.

Making Your Own Lawn Sand

Making your own is easy, and it is more effective than a shop mix because you know exactly what is being applied. The iron is soluble sulphate of iron, which we sell in the shop: it is the same product I use on bowling greens and by far the most cost effective moss treatment there is. If you are outside our delivery area, Elixir Gardens soluble sulphate of iron is the same thing in a 5kg bag. You can also buy it ready dissolved if you do not want the bother of mixing, but the powder is cheaper.

The simplest way to use it is dissolved in water and put on with a watering can or a sprayer, at the rate on the bag, on a still day when the grass is dry. If you would rather spread it dry, the old way, mix dried sand with the iron at a ratio of one kilo of iron to five kilos of sand. Mix it thoroughly in a barrow or a bucket, keep it dry, and put it on with a spreader at around fifty grams of the mix per square metre when rain is expected within a day or two. Any clean dry sand will do, and a bag of kiln dried sand from the paving aisle is the easiest to mix and spread because it is already dry. Either way, the moss will blacken within a week or two and can then be raked out.

Two warnings. Sulphate of iron stains: keep it off paths, patios and stonework, and sweep up any spill before it gets wet. And do not apply it in frost or when the ground is frozen, as it will scorch the grass along with the moss.

Coming Out of Winter

If you follow this advice, along with the other maintenance practices I advocate elsewhere on this site, the lawn will come out of the Winter in good condition, ready to take advantage of the new spring growth. The February application of iron is the bridge into the new season: it takes out any moss that has crept in over the Winter so that the first proper feed goes to the grass and not the moss.

For that first feed of the year I switch to a high nitrogen, high iron product. Our Spring Turf Care, 9.0.0 with 11% iron, is the one I use, and the rest of the year’s programme is in my article on the best fertilisers for spring and summer.

If You Look After a Bowling Green

Everything above holds for a green, with the feed going on as part of the autumn renovation programme, after the aeration and scarifying and before the top dressing. The full feeding programme for the year is in the fertiliser section of my definitive guide to maintaining a bowling green, and the timings month by month in a full year’s maintenance of a bowling green. Clubs that would rather have the whole year’s materials arrive in one go, with advice included, should look at the bowling green package.

If you are not sure what your lawn or green needs, get in touch and I will point you in the right direction.