Topping can and should be done during or near the end of flowering, when the flower caps have fallen if possible. Topping during this period redirects sap flow towards the future bunches and reduces the shatter rate. This results in a better setting of the fruit. There is also a practice called double topping where the vine is topped at the beginning and middle of flowering. This practice is very restrictive but very efficient in combating excessive vigour and coulure, and may be used preferentially for certain grape varieties such as Grenache. This practice should not be carried out too early relative to flowering, as this risks redirecting the sap and the formation of side shoots.
Trimming (horizontal and lateral) on the other hand does not need to be done early, quite the contrary. Delaying trimming as much as possible will reduce compensation phenomena and regrowth, thereby reducing the number of times machinery has to pass over the plot.
Generally, for trellised vines, the first trimming takes place between the fruit set and véraison. It can be done earlier if the vine is very vigorous and threatens to restrict the passage of machinery between the rows. Subsequent trimmings do not follow specific guidelines but depend on the vines' regrowth and the threat of fungal diseases. However, to maximize the effect of subsequent trimming, there are some factors to take into account:
- Trimming before a treatment facilitates the access of the product to target organs
- If the vine has suffered a significant outbreak of downy mildew, the young organs affected can be trimmed to avoid another treatment.