Using grass cuttings and comfrey for orchard fertility

Why orchard fertility works differently

In a fruit tree, the roots that matter are shallow. The fibrous feeding roots sit in the top 10–15cm of soil, fanning out well beyond the canopy, and they are in direct competition with the grass beneath them. Left alone, a mown orchard floor is a hungry place: the grass takes moisture and nutrients first, and the tree gets what is left. That is why the old orchard practice of simply scattering fertiliser never quite delivers. You are not really feeding the tree. You are feeding the soil life that feeds the tree, and that process is slow, damp and full of invertebrates.

This is where a mulch of grass cuttings and comfrey leaves earns its place. Both are materials most English plots produce in unreasonable quantity, both break down readily in our mild, moist climate, and both can be laid straight on the ground without a compost heap, a shredder or a single bag of bought feed. Done well, you get weed suppression, moisture retention and a steady release of nutrients across the whole growing season rather than one nitrogen spike in April.

Comfrey: the cut-and-drop crop worth its space

If you keep fruit trees and have not yet planted comfrey, put it on this autumn's list. Use Bocking 14 — a sterile form of Russian comfrey that sets no viable seed and will not march across your plot. It is a deep-rooted perennial that mines potassium and other minerals from below the reach of most roots, then donates them back through its leaves.

The leaves are rich in potash, which is exactly what fruit swelling and ripening demand, with useful nitrogen and calcium alongside. A bed of half a dozen plants will keep a small orchard in mulch indefinitely.

• Plant crowns about 60cm apart in a sunny spot, ideally somewhere you can reach with a barrow.
• Take the first cut in late May, when flowering stems start to form, slicing about 5cm above the crown.
• Cut again every six to eight weeks, giving four or five cuts a season before the plants die back in October.
• Let the leaves wilt for a day before spreading — they slough less and settle into a mat that slugs dislike.

Cut comfrey can go straight under the trees, a couple of inches thick. It shrinks alarmingly within a fortnight and disappears into the soil by autumn.

Grass cuttings: free mulch, handled with care

Clippings are roughly four-fifths water and carry a useful slug of nitrogen, which makes them excellent material and a genuine hazard at the same time. Dumped in a thick, undiluted heap around a trunk, they heat, mat and turn to a sour, airless slime that smells of rot and can encourage soft fungal problems at the base of the tree.

The rule is thin and often. Scatter clippings in layers no more than 2cm deep, letting each layer dry and darken for a week or two before adding more. Mix them with comfrey, chopped bracken, shredded cardboard or a little woodchip if you have it — anything carbon-rich opens up the mat and keeps air moving through.

Two cautions. Do not use clippings from a lawn treated with a selective weedkiller, as some residues persist in the material and show up as twisted, cupped leaves on young trees. And avoid clippings full of seeding dandelion or buttercup heads unless you are content to grow them everywhere.

How to build the mulch ring

Work outwards from the trunk, never inwards. Start your ring 10–15cm clear of the trunk and take it out to at least the drip line, further on a mature tree. A young maiden might get a ring a metre across; an old standard will happily take one four metres wide.

• Aim for a settled depth of 5–8cm in total, built up in layers rather than all at once.
• Alternate comfrey and clippings, or mix them roughly half and half by volume.
• Water the layers lightly if the soil beneath is dry, so the mulch knits down instead of blowing about.
• No digging in. The worms will do the incorporation, and they will do it better than a fork.

Keep that bare collar of soil around the trunk. Damp mulch pressed against bark is an invitation to collar rot, and on a grafted tree it is worth leaving the union completely exposed.

A year of mulching

Late April, when the soil has warmed but not dried, is the best time to start. First clippings arrive with the first real mow, and they can go on thinly from then on. From late May to September, comfrey cuts every six to eight weeks give you four generous applications, each laid after the previous one has settled.

By early October, stop feeding and let the rings settle. Before winter, pull the mulch back 15cm from every trunk — a deep, dry mulch is a favourite winter residence for voles, and they will happily gnaw bark under snow cover. Leave the bulk in place to protect the soil from leaching rain, then check and top up the rings in February while the trees are still dormant.

Mistakes worth avoiding

Most disappointments come from doing too much at once. Avoid thick, wet clippings smothering a waterlogged clay soil in January, which starves roots of oxygen for months. Avoid mulching frozen ground, where materials sit inert and simply go mouldy. Avoid expecting miracles in the first season — the visible difference, in leaf colour, shoot growth and fruit size, usually shows in the second or third year, once the worm population has moved in and the soil beneath the ring has darkened and crumbled.

Do it patiently, though, and you end up with something better than a fed tree: an orchard floor that holds moisture through a dry July, smothers the weeds you used to strim, and quietly builds the sort of deep, crumbly soil that fruit trees seem to repay for decades.