Definition - What does Tertiary Bud mean?
The tertiary bud is one of the three buds contained in the compound bud. They are labeled as; primary, secondary and tertiary. The main purpose of the tertiary bud is that it is usually the latter bud which can survive the winter or in the case of late frosts.
It is also the only bud which becomes vegetative and breaks through following the winter dormancy period.
WineFrog explains Tertiary Bud
The tertiary bud is often grouped together with the secondary bud as it is sometimes difficult to observe.
The primary, secondary and tertiary bud are packed together in a group of external scales within a compound bud and is the axillary bud from a lateral bud.
The tertiary bud is smaller and less developed than the others, but is important in the case of vine damage due to seasonally poor or extreme weather events. It is often seen as a "back-up". However, if the surviving bud is the tertiary bud, they often do not produce flowers or fruit.