Grass care; sward for fertility

Although a kitchen garden rarely has place for a lawn as such it most certainly may contain some mown grass sward usually in the form of pathways. These are primarily functional but also have a visual aspect which we normally wish to maintain. I now wish to introduce the idea of using the sward as a fertility generator. First however I have to explain the tremendous value of grass clippings and their utilisation as a free home grown organic fertiliser and mulch.

Many of us simply add our grass clippings to the compost heap which is fine as added in thin layers they break down easily and contribute valuable nutrients. Green grass clippings are rich in nitrogen, especially when cut during strong growth, and so mixing in fresh clippings when turning a compost heap will really make it cook. It is hard to compost dried grass, hay or straw from mature plants as they are low in nitrogen and will not rot down readily on their own. If these are mixed intimately with fresh grass clippings, moistened and inoculated with some real garden compost they then compost exceedingly well.

Hot beds used to be made from horse manure, straw and leaves, instead I use grass clippings and straw, thus cutting out the horse. I make them in my polytunnel, they work so well I can grow fantastic melons, watermelons and cucumbers with no other heat. (Melons like plenty of lime, preferably calcified seaweed, adding to their beds)

I have also found just mixing in a handful of fresh clippings really enriches the potting-on compost for hungry fast growers such as courgettes and squashes though tomatoes do not seem to like it as much. However potatoes that have grass clippings mixed in with the soil when they are planted not only grow better but the clippings are attacked preferentially by scab and the tuber skins stay much cleaner. Also once the potato leaves and stems are a few inches tall they can be earthed up with grass clippings instead of soil; no more than an inch or so at a time or they go claggy. When the tubers are dug up any gross amounts of clippings can be removed with the dead haulm but much will have disappeared already and all will have gone by spring.

The addition of grass clippings makes for a very rich friable soil; it seems to encourage micro-life activity more than the simple fertiliser equivalence would suggest, in particular it encourages worms. Wormholes aerate and drain the soil, worm casts are very rich in nutrients and they are also water stable so making that brown sugar texture loved by plants. I have observed vast numbers of worm casts appearing where small amounts of clippings are added but not where the clippings were applied so heavily they went claggy. (This may be due to the silage juices generated being too acid for worms to tolerate.)

You may have noticed the way the larger worms feed is to drag leaves and such like into their burrows; onion sets often up-end as the dead leaf is pulled in. So I feed the worms 'greens', over every square yard of bare soil I lightly sprinkle a handful of fresh mowings whenever I cut the grass. The benefit to fertility is immense as worms easily produce casts at rates of more than fifteen tons per acre, if fed well! Being high in nitrogen clippings do not rob the soil if dug in but simply applied to the surface they are soon incorporated anyway. They can be applied more thickly and make very good mulches when applied an inch or so deep under brassicas and sweet corn and on either side of rows of peas and beans. As long as the mulches are never put on so heavy they go claggy then they disappear rapidly and can be topped up each time the grass is cut.

Flushes of weeds can also be effectively controlled with grass clipping mulches; each and every week you just add another inch layer on top of any weeds that have made it through. Meanwhile underneath both the clippings and the dying yellowing weeds are breaking down and feeding the soil making it even richer while keeping it moister. If large amounts of clippings can be produced then they are also excellent used around all soft fruit excepting strawberries. Of course in the orchard it is common practice to put the mowings in circles under the trees but these tend to be more mature and less nitrogenous though they still benefit the soil and tree immensely.

Thus as they are such a boost to fertility a kitchen garden needs as many grass clippings as can be obtained. Obviously clippings can be brought in from elsewhere but care must be taken to ensure none are imported that come from grass treated with weed or moss killing chemicals as this could adversely affect the crops were these then to be applied to them. However as many gardens have grass paths already these can be encouraged to produce as many clippings as possible, while still remaining usable and attractive. Fortunately all these parameters can be met, and the same methods give an excellent finish worthy of a lawn - though in no way producing a bowling green.

Most grass swards are composed of a mixture of grasses; tough hard wearing ones and finer sorts. Depending on local conditions, the length established and the treatments undergone this mixture will vary. True bowling green grasses are very fine but require acid conditions. The tougher more vigorous grasses prefer limy. This suits the kitchen garden as whenever we lime, at least every fourth year, then we can lime the grass.

In fact it is worth liming the grass more frequently for several reasons; Worms love lime so it also helps them thrive, lime discourages difficult weeds that like acid soils such as many mosses and veronica speedwells, lime improves the flocculation and drainage of heavy soils so further discourages mosses. Most of all clover likes lime, clover and grass grow better together than grass on it's own. (You can avoid having green clover patches in a sea of browned out droughted lawn by over-sowing with clover seed, then it stays green everywhere.) Clover not only gives nitrogen to the grass but also attracts the dew keeping the soil moister.

Grass sward itself will also attract more moisture if it is left with longer leaves, and longer leaved grass loses less moisture from the soil than very short cut grass. Longer grass also grows faster and roots deeper. Thus if you cut your grass as often, say weekly, but set the blades to cut higher then you get more growth each week and more clippings to remove. The greater depth of leaves also suppresses weeds more effectively and cutting with the blade set higher slowly gets rid of daisies and other low growing weeds. Those that are rosette forming such as plantains, dandelions and thistles may survive but are easily removed by grubbing out with a sharp knife.

Grass clippings are most value for fertility used earlier rather than later in the year. So it makes sense to 'bank' your clippings; this means raising the height of cut progressively further as summer goes into autumn and then cutting progressively lower and lower during spring to a minimum when growth is at it's peak in late May early June. This also helps the grass stand through winter as it is tougher when the longer blades protect the roots.

Grass paths tend to wear in the middle and where you stop to turn or enter a gate. These spots remain unsightly, produce no clippings and give a foothold to weeds which have a seeding tendency such as annual meadow grass. It is better to replace these bare patches with set in stepping stones or slabs. These give less muddy footing and they mulch the surface throwing water off to benefit the sward all around. In a three foot wide path setting a one foot wide row of slabs increases the rainfall to the turf by half again keeping it much greener. For minimum expense and for ease of wheelbarrowing I lay a path of slabs corner to corner bedding them on sand.

Of course one of the easiest ways to increase the yield of clippings is to add fertility to the turf. Too much though and you check the clover and stop getting as much nitrogen fixed for free. I find fresh well diluted urine to be the best feed though comfrey, borage & nettle tea does almost as well. Dressings of sieved compost or well rotted manure are of benefit and top dressings of coarse sand help open up a heavy soil. A seaweed spray once a month helps the sward become healthier and resist disease. If the grasses are poor varieties or the sward is very weedy then oversowing with tough grass seed in spring or autumn will dramatically improve it.

Those who wish to go for the maximum could also rake out dead thatch and moss then spike and aerate the sward before oversowing and then top dressing, following this with a rolling or three a few months later. But there is no need for all this effort, just cutting the grass higher improves the turf immensely.