Why a clean cut matters more than you think

A sharp pair of secateurs is the difference between pruning and mauling. When the blade is keen, it slices through a stem cleanly, leaving a smooth wound that calluses over in days. When it is blunt, it crushes the tissue, leaving a ragged edge that dries out, dies back and gives fungal spores an open door. Add a film of sticky sap and a spot of rust, and you are also carrying disease from plant to plant on every cut.

Pruning shears do not ask for much: a wipe down after every session, a proper clean and sharpen once a season, and a drop of oil on the pivot. Ten minutes in the shed in autumn, before the winter pruning really begins, will see you through the whole year. If you are cutting a lot of hardwood, or working through a big hedge, sharpen more often — every ten to fifteen hours of cutting is a sensible guide.

What you'll need

• A small flat file, a diamond sharpening file or a sharpening stone. A diamond file is the easiest to use on curved blades.
• Fine wire wool, grade 0000, or a fine abrasive pad.
• Methylated spirits, or warm soapy water and a stiff brush.
• An old toothbrush for getting into the pivot and spring.
• A light machine oil, camellia oil or a specialist tool oil.
• Clean rags and a small bowl.

Step one: strip the sap and grime

Take the shears apart as far as they will go. Most models have a central bolt you can undo with a spanner or a coin, which lets you separate the two blades and the spring. Losing a spring in the long grass is a classic, so work over a tray or a cloth.

Soak the metal parts in warm soapy water for a few minutes, then scrub with the toothbrush, paying attention to the pivot, the spring and the inner faces where the blades rub together. Plant sap is sticky and slightly acidic, and it hardens into a varnish-like film that will gum up the action. For heavy resin — conifer sap is the worst offender — wipe the blades with a rag dampened with methylated spirits. It cuts through the stickiness in seconds. Dry everything thoroughly with a cloth; trapped moisture is what starts rust.

Step two: tackle the rust

Light surface rust is easy to shift. Rub along the blade with fine wire wool, working in the direction of the blade rather than across it, until the orange bloom lifts and you can see bare steel again. A little oil on the wire wool helps it cut through the corrosion.

For heavier pitting, use a fine abrasive pad with a few drops of oil, or a scraper to lift the worst of it before finishing with wire wool. Do not be tempted to attack rust with coarse sandpaper — you will scratch the blade and create new places for moisture to sit. Once the metal is clean, wipe it down and oil it straight away, because freshly cleaned steel rusts within hours in a damp shed.

While you are at it, disinfect the blades. Wiping them with methylated spirits between plants is a simple habit that stops you spreading blackspot, box blight and canker around the garden on a blade that looks perfectly clean.

Step three: sharpen the bevel — and only the bevel

This is where most people go wrong. Bypass secateurs have a single bevelled edge on the cutting blade and a flat face on the other side. You sharpen the bevel. You never touch the flat side, because that flat face is what meets the other blade and gives you a clean, scissor-like cut. File it and the two blades will no longer close properly.

Match the existing angle — usually around 20 to 25 degrees, so the file sits almost flat against the bevel with the spine lifted a little. Push the file away from you along the curve of the blade in one smooth stroke, following the shape of the edge rather than filing in a straight line. Lift the file on the return stroke so you are only cutting in one direction. Eight to ten strokes is usually plenty; check the edge against the light for a thin, bright line of fresh metal with no glinting flat spots.

Anvil secateurs are different: only the single curved blade is sharpened, and the flat anvil is left alone. If the anvil is scored or worn, replace it rather than filing it.

Reassemble, oil and store them properly

Put the shears back together and tighten the central bolt so the blades meet with a whisper of friction — snug, but not so tight that the handles are stiff. Too loose and the blades will tear rather than cut; too tight and you will strain your hand and wear the pivot.

Oil the pivot, the spring and both faces of the blade, then work the handles a few times to spread it. Test the edge on a piece of paper: a properly sharpened pair should slice cleanly through, without snagging or folding the sheet. A soft green stem is an even better test.

Store them dry, with a light coat of oil, somewhere out of the rain — hanging on a shed wall rather than lying on a damp bench. A quick wipe and a drop of oil after each use, and your shears will reward you with years of clean, healthy cuts.