The Vine Part 1

Overview

This session (WSET Level 4, Wine Production) introduces vine anatomy Part 1, focusing on main shoots, stems, buds, and lateral shoots.

Vine Structure: Four Main Sections

• Vines share a similar overall structure across varieties.
• Four sections: main shoots, one-year-old wood, permanent wood, and roots.
• Main shoots include stem, buds, leaves, tendrils, flowers, and grape berries (the canopy).
• One-year-old wood is last year’s growth that has lignified (hardened).
• Permanent wood includes trunks and cordons; roots absorb water and nutrients.
• Later parts will cover leaves, flowers/berries, and permanent wood in detail.

Main Shoots: Nodes and Internodes

• Main shoots originate in spring from buds retained from the previous year.
• Retained bud number depends on winter pruning decisions.
• Nodes are swellings on the shoot where organs are attached.
• Internodes are the stem segments between nodes.
• Canopy refers collectively to all green parts on the vine.

Stem (Vascular System)

• Vines are vascular plants; the stem is the transport and support structure.
• Phloem transports sugars (glucose) and nutrients throughout the plant.
• Xylem transports water/sap, driving hydration and sap flow.
• Stem transports water and solutes to/from vine parts; stores carbohydrates.
• Carbohydrate storage supports growth and the winter dormancy phase.

Seasonal Change and Lignification

• Late summer to autumn: leaves turn golden/yellow/brown and fall.
• Green shoots and tendrils lignify, becoming brown, rigid, woody.
• Winter pruning (late winter: Feb–Mar in Northern Hemisphere) removes excess wood.
• Pruning retains necessary structure and buds for next season’s growth.
• Lignified prunings may be composted, left on ground, or burned.

Bud Types and Functions

• Buds form between the leaf petiole (leaf stalk) and the main stem.
• Buds contain pre-formed structures for future shoots, leaves, tendrils, flowers.
• Two types: compound (latent) buds and prompt buds.

Compound (Latent) Buds

• Form in one growing season; break in the next if retained at pruning.
• Produce the main shoot in the following season.
• Contain primary, secondary, and sometimes tertiary buds.
• Secondary/tertiary buds can grow if primary is frost-damaged.
• Later growth shortens season length and can affect ripening.

Prompt Buds

• Form and break within the same growing season on the current main shoot.
• Produce lateral shoots during that season.

Lateral Shoots: Roles, Benefits, and Issues

• Lateral shoots are smaller/thinner than main shoots; arise from prompt buds.
• They have stems, leaves, buds, tendrils, and sometimes inflorescences.
• Primary role: maintain growth if main shoot tip is damaged or destroyed.
• Benefit: add foliage near canopy top, enhancing photosynthesis and sugar production.
• Problems: divert energy from main shoot; impede airflow; increase disease risk.
• Excess shading by laterals can reduce fruit exposure and affect ripening.
• Summer pruning and de-suckering remove unwanted laterals; labor-intensive work.

Second Crop from Laterals

• Laterals can bear inflorescences, forming a “second crop.”
• Common in some varieties; Pinot Noir often shows a second crop.
• Second crop lags behind main crop; ripens later than primary fruit.
• Strategic growers may harvest second crop later if weather allows.
• In high-volume or machine-harvested vineyards, second crop is often removed.
• Under-ripe second crop can raise acidity, add greenness, and lower sugar.
• In rare cases, later fruit may counterbalance an overripe main crop.

Key Terms & Definitions

• Canopy: All green parts of the vine (leaves, shoots, tendrils, flowers, berries).
• Node: Swelling on a shoot where organs (leaves, buds) attach.
• Internode: Stem segment between two nodes.
• Phloem: Vascular tissue transporting sugars and nutrients.
• Xylem: Vascular tissue transporting water/sap.
• Lignification: Process converting green tissue to rigid, woody tissue.
• Compound (Latent) Bud: Bud formed one season, breaks the next; contains primary/secondary buds.
• Prompt Bud: Bud that forms and breaks in the same growing season.
• Lateral Shoot: Secondary shoot from a prompt bud; supports continued growth.
• Inflorescence: Cluster of flowers that can develop into grape berries.
• De-suckering: Removal of unwanted shoots, often lateral shoots, during the season.

Vine Structure Summary Table

Action Items / Next Steps

• Continue to Part 2: leaves, flowers, and berries in greater detail.
• Review pruning strategies impacting bud retention and shoot development.
• Understand management of lateral shoots to balance canopy and fruit exposure.