Fundamentals of skeleton formation and pruning methods for grapevines

For convenience of maintenance and mechanization of operations in vineyards, increasing the productivity of plantations and the quality of produce grape plant — a multi-stemmed vine — is trained into a bush form. In its aerial part, the following are distinguished:

• Perennial organs — the skeleton, consisting of the trunk, the head, and perennial branches (arms).
• Annual organs — shoots with buds, leaves, tendrils, and inflorescences or clusters.

Trunk — the perennial part of the stem from the soil surface to the first branching (arm). In certain forms, most often in the covering zone, it is absent. Such forms are called trunkless or low-growing. Depending on the height of the trunk, bushes are classified as:

Head — the upper part of the trunk, or the base of the bush in a low-growing form, on which the arms develop. In some forms, it is absent or poorly developed, while in others, it is overgrown.

Arms — perennial branches extending from the trunk or the head (in some forms, they are called shoulders). They can be permanent, formed for the entire lifespan, or growing, increasing in length from year to year due to a portion of the fruit shoots left during pruning.

The functions of the trunk, head, and arms are manifold: they serve as support for shoots with fruiting structures and leaves, ensure the interconnection between leaves and roots, acting as organs that conduct nutrients and plastic substances; storage substances used by the plant for building new organs accumulate within them. The habitus, structure, and shape of the bushes depend on the size of the trunk, the number and length of the arms, and their spatial arrangement.

There are 3 methods for forming the trunk and arms:

1. Slow method — bush formation is carried out gradually, over a number of years, by sequentially extending the skeletal part using one or more matured shoots cut to the required length. The trunk and arms are thickened and evenly distributed in space. This method is used in all zones on bushes of varying vigor. Due to the delayed creation of the skeleton, plants enter fruiting later than with other formation methods. There are many wounds on the bushes.
2. Accelerated method — consists of leaving one well-developed shoot on the bush, which is pruned to a long length (up to 1.5 m). At the height of the future trunk, part of it is bent horizontally and tied to the trellis wire. This method is used under conditions of good nutrition and water supply on vigorous cultivars. Already in the year following the shoot bending, a harvest is obtained. The bushes develop relatively thin trunks and perennial branches, with fewer wounds.
3. Rapid method (after Bashirov, 1959) — is based on the use of pinching growing shoots to obtain artificially developed lateral shoots, which are used to form arms and fruit shoots. It is used under conditions favorable for the maturation of lateral shoots and for cultivars with good lateral shoot-forming ability. This accelerates the plant's entry into fruiting.

Fig. 43. Parts of a grape bush: 1 — underground trunk; 2 — primary roots; 3 — lateral roots; 4 — surface roots; 5 — trunk; 6 — permanent arm; 7 — growing arm (spurs); 8 — renewal spur; shoots: 9 — fruit; 10 — fruit-bearing; 11 — barren; 12 — lateral; 13 — vigorous (water shoots); 14 — basal; 15 — restoration spur.

Shoots also determine the type of form. They have different names depending on their origin, location on the bush, pruning length, and spatial arrangement.

Basal shoots that developed from dormant buds on the underground trunk, and vigorous (water) shoots that also developed from dormant buds on the trunk, head, and at the base of the arms, pruned short (to 1–4 buds), are called rejuvenation, restoration, or lowering spurs, depending on their purpose.

Matured shoots (with buds) at the end of growing arms are called fruit shoots. They are potentially fruit-bearing because embryonic inflorescences develop within their buds.

There are 4 types of pruning fruit shoots">fruit shoot pruning: short — to 1–4 buds, medium — to 5–10 buds, long — to 11–24 buds, and mixed (or combined) — to a fruit link, where the lower shoot on the arm is pruned short and the upper one is pruned to a medium or long length.

Depending on the pruning length, method of tying, and spatial arrangement, fruit shoots are called: a cane, if pruned long (more than 12 buds); an arrow — if pruned to 5–11 buds and positioned without bending horizontally, vertically upwards or downwards, or obliquely upwards or downwards; a semi-arch — with the same pruning length and spatial arrangement, but bent into a semi-arch shape; an arch — when tied with a sharp bend; a ring, when formed into a ring shape; or a spiral, if bent into a spiral.

Short-pruned fruit shoots (to 1–4 buds) are called spurs. If a short-pruned fruit shoot is located below a medium or long-pruned one on the same arm, it is called a replacement spur. The combination of short and medium or long-pruned shoots on the same arm is called a fruiting unit.

Managing the productivity of a grapevine directly depends on how the shoots are distributed in space and the length to which they are pruned. By directing the growth of the bush through proper training, an agronomist regulates the longitudinal and transverse polarity of the plant, as well as its metabolism. In modern viticulture practice, four main types of fruiting units are used, each of which has its own characteristics for bud distribution.

Four types of grapevine fruiting units