Bud Phenology

This morning my husband came across an article called "The morphological evolution of bud break". In this article, there are some very good photos of the grape bud at various stages prior to budbreak. This year, when we are closely monitoring our buds, it is very interesting to see an illustration that corroborates what we are seeing!

• Stage 00 (a): In all cultivars, a conic shape, rounded at the base, with the brown bud scales strictly closed, characterizes the complex system of the ‘dormant bud’.
• Stage 01 (b): At the end of the rest period, a swelling of the bud and the consequent appearance of a white wool tip is the first morphological change.
• Stage 03 (c): A swelling of the bud then causes the bud scales opening as a consequence, the bud enclosed by the white wool is observed.
• Stage 05 (d): The bud appears enclosed by brown wool and is characterised by a complete opening of the bud scales.
• Stage 07 (e): This stage, the so-called “greentip” bud stage, is generally considered as the indicator of ‘budbreak’: the green leaf tips break through the brown wool and are just visible.
• Stage 09 (f): The last phase of bud development is complete bud opening, during which the new leaves are clearly visible.

We have noticed that our Auxerrois and our Chardonnay buds are still very tightly closed and our Chenin Blanc is the most advanced.
References:
1. L. Andreini, R. Viti, and G. Scalabrelli, ""The morphological evolution of bud break in Vitis vinifera L.", Vitis, 48 (4), 153–158 (2009).