Pruning and Training

The first pruning commences in late March. Late pruning aids in the delay of bud burst, thus hopefully avoiding the late spring frost, which could destroy the young buds.

The second pruning is known as trimming. This is carried out in the summer and goes hand in hand with canopy management.

The pruning system followed is cane pruning. Cane pruning retains a high proportion of buds from the fruitful middle section of the cane; this helps increase productivity during the period when the inflorescences are formed. (Generally during this period, temperatures are low which contributes to the low productivity of the buds, therefore cane pruning is the preferred).

The basic cuts needed for cane pruning originate from the crown of the permanent vine trunk. All old wood from the vines after pruning is collected, weighed and then removed and burnt. This helps prevent fungal infection by minimising the spread of the infection to both the remaining wood and the soil or grass.

Data from the weighed wood is collected and from this data one can determine the productivity of the wood and thus the crop.

The method followed at Danebury is called the Double Guyot system. The basic principal of this system, devised by Dr Jules Guyot in 1860, is to leave two canes either side of the crown with 10 buds on each cane and spurs at the base of each cane with two buds; the shoots from these spurs will form the canes for the following year.

The number of buds left at pruning is critical as too many buds may increase yield and but delay maturity.

The canes are then tied down onto the first wire (growing wire) of the trellising. This method of training is called Vertical Shoot Positioning or VSP (see below). The choice of the training system is important, as it goes hand in hand with canopy management.

Light quality has a very important effect on the quality of wine produced. Low light quality can produce a high pH and acid and low sugars and it tends to delay maturity and impairs colour development.

The quality of the light intensity is also a main contributor to the amount of flowers a bud will produce. More flowers will be produced if in the previous season the bud and adjacent leaves received more light whilst the bud was being formed.

It is vital to maintain good canopy practices. Training the canes down onto the growing wire either side of the crown reduces overcrowding and bunching and encourages maximum light intensity around the spurs and buds for the following years crop.

Good canopy management should be maintained once the inflorescence and flowers have been formed. With good canopy management the flowers will have a high chance to convert into an adequate crop. This conversion is known as fruit set (also known as coulure).

There are several factors that need to be considered to encourage a successful fruit set, light intensity, rain and temperature. It is worth noting that (i) Heavy shading of the inflorescence by leaves will lead to early bunch-stem necrosis, which could lead to 100 percent of the bunches being infected and so heavy losses in the crop yields. (ii) Cool and wet conditions can contribute to poor fruit set. An open canopy can help reduce the drying time after rain and so minimise the risk of poor fruit set.

Canopy management will also contribute to the flavour of the wine as (i) higher sugar levels can be achieved if the ratio between leaf and fruit is correct, which in turn produces quality wines, (ii) the pH and potassium can reach levels through high shading which could be detrimental to quality wine production (iii) high quantities of the chemical compounds known as Methoxypyrazines can, through heavy shading of the grape bunches, pass a green grassy aroma onto the wine.

Trellis

The VSP system used at Danebury is the most common in cool climates.

The growing wire along which the cane has been trained is about 6 inches below the foliage wires, which are normally doubled up and set in 3 positions at varying heights up the trellis posts.

As the shoots along the canes begin to grow they are supported between the two narrow bands of wire to protect from wind damage.

This support encourages a narrow canopy, which can be maintained by summer trimming of the lateral shoots and so reducing shading and volume of canopy.

The shoots grow to a height of 10 to15 leaves above the growing wire. This amount of leaf ratio to bunch of grapes per vine has been found to be the most beneficial for crop production.

The first summer trimming is carried out after cap fall.