6-Millimetre Spur Pruning on a Vitis Vinifera Rod Trained Along Galvanised Wire

Six millimetres at the dormant bud

A spur cut on Vitis vinifera is placed 6 millimetres above the retained bud, with the distance taken from the base of the bud scale to the cut face. At less than 3 millimetres, the inward drying of the pruning wound during dormancy can reach the retained bud. Once the stub is left 15 millimetres or longer, it becomes a dead snag that fails to compartmentalise and allows Eutypa lata spores through exposed xylem. Trials on cordon-trained vines in temperate regions have repeatedly put the safer margin close to half a centimetre.

Distance alone is insufficient if the face of the cut holds water. A level wound can leave water sitting on the exposed surface, while a blade set at roughly 20 degrees, falling away from the bud, lets the wound drain. On a two-year-old cordon with eight to twelve spur positions, the dormant pass reduces each spur to two buds, which gives the rod a crop load it can ripen without shading its own fruit. The wire carrying the cordon keeps that arrangement straight enough for the same count to be repeated.

Wire gauge, tension, and a readable cordon

Most commercial and domestic cordon systems use hot-dip galvanised wire from 2.5 millimetres to 3.15 millimetres in diameter. The coating resists the zinc-consuming acidity produced by vine sap and rain runoff, and the wire gauge helps hold the rod in a fixed horizontal line.

A rod tied tightly to 2.5 millimetre wire at single tie points every 300 millimetres keeps its spurs evenly spaced. When the secateurs come out in winter, that spacing makes the bud count visible along the cordon.

Sag changes the distribution. Spurs tend to cluster at the low point, so one section is overcropped while another is left short. Bringing the wire up to tension with a Gripple or ratchet strainer before the dormant cut is part of establishing even spur positions.

The zinc coating also changes what happens to the tool. During tie removal, blade steel dragged repeatedly across galvanised wire picks up a zinc smear. The smear does not injure the vine, yet it dulls the cutting edge faster than plant tissue alone.

On a long cordon run, pruners commonly strop or hone a secateur blade two or three times during a morning for that reason. The difference shows up most clearly when hundreds of small cuts must land within a few millimetres of the same point.

Wire height affects the body position behind the cut. Fruiting wire set 900 millimetres to 1100 millimetres above the soil brings spur positions to a working height that removes the crouch, and a pruner standing upright places the 6 millimetre cut more accurately than one bent double over a low cordon.

Bypass secateurs, anvil pressure, and live rod

Bypass secateurs slice live rod by passing a curved blade past a fixed hook, whereas anvil secateurs press a single blade onto a flat surface and leave crushed tissue beneath the cut line. That difference is decisive on a 6 millimetre spur because the retained bud sits close to the wound.

Bypass models such as the Felco No. 2 and the Niwaki GR Pro work cleanly through green and semi-lignified rod up to about 10 millimetres. The cut face remains smooth and seals quickly. Anvil secateurs bruise the tissue below the cut, and the crushed zone can die back into the retained bud on a spur shortened to 6 millimetres above it.

Blade orientation on a bypass cut is deliberate. The flat blade faces the retained spur, and the hook carries the discarded piece. If the hook is placed against the spur, the opening blade levers the retained stub and can tear the side that has to survive. A pruner working a Felco No. 2 through several hundred spurs keeps the blade toward the vine on each stroke, then rotates the wrist along the horizontal cordon to maintain that position.

When rod diameter has lignified beyond normal secateur capacity, above roughly 12 millimetres, a Felco loppers pass replaces the hand tool. Old cordon wood follows the same 6 millimetre logic, although the cut needs two hands and a fully seated blade before the stroke closes. A partial loppers cut on hard wood can split the rod lengthwise, and the split may run into living tissue.

Notching where a spur has died out

A bare stretch on a cordon can be refilled by notching above a dormant bud. The cut is shallow, about 2 millimetres deep, placed across the bark immediately above the bud and 1 to 2 millimetres clear of it. It severs the phloem on the upper side, interrupts the downward flow of auxin from the shoot tip, and releases the bud from apical dominance so it breaks the following spring instead of staying latent.

Notching is carried out in late dormancy, close to bud swell, which prevents the wound from sitting open through the coldest weeks. A knife or the tip of a bypass blade makes the notch, with depth controlled by wrist pressure without a mechanical guide. Too deep a cut girdles that side of the rod and kills everything above it. On galvanised-wire cordons, notching repairs the missing position while preserving the established fruiting wall, so a whole new cane does not have to be laid down.

Bud count before the first cut

Count before cutting. A mature cordon on a domestic training wall carries many more dormant buds than the rod can ripen, and the dormant pass removes the excess until the vine can crop without overreaching.

Take a 1.5 metre cordon with ten spur positions at roughly 150 millimetre spacing. Each position from the previous season carries two canes, and each cane has five to eight visible buds. Left untouched, the cordon presents about 120 to 160 buds.

The winter cut reduces each of the ten positions to a single two-bud spur, leaving twenty buds. Each cut sits 6 millimetres above its upper bud. The lower bud on each spur becomes next season’s fruiting shoot, and the upper bud becomes the following season’s renewal spur, so the cycle continues along the same wire.

Leaving forty buds instead of twenty doubles the shoot count, cuts the light reaching each bunch, and delays ripening by weeks. The crop is governed by retained bud count, while the length of any individual cut protects the bud that has been selected.

Stooling beds as the rough comparison

A stooling bed is cut to a stub. In a hard-pruned stooling bed, a shrub grown for cutting material, such as coppiced Cornus or Salix, is taken down each dormant season to within 50 to 75 millimetres of the ground to force a flush of straight, vigorous shoots. That system has no fruiting position to preserve, and the Niwaki hedge trimming habit of cutting to an outward-facing bud to steer growth away from the centre is absent because the stool is intended to send all new growth upward at once.

A grapevine spur sits at the fine end of that pruning range. A stooling stub can recover from a crushed anvil cut because regrowth comes from the base, while a 6 millimetre grape spur carries only the two buds assigned to the next crop. A heavy anvil lopper taking 30 millimetre wood in one crush may suit a Salix stool and still make unusable grape spurs.