Monday, July 09, 2007

Pruning Grapevines

The most important job in the vineyard during winter is pruning. This is done after leaf fall but before budburst when the vines are dormant and there is virtually no sugar transfer from shoots to roots.
One of the reasons for pruning is that grape bunches only grow on new shoots and it is necessary to get rid of most of the old growth from the previous season. But there is more to it than that. The vine has to be maintained in a workable shape that will facilitate vineyard management practices such as spraying and harvesting. Pruning also achieves a balance between vegetative and fruit growth which basically means there should be enough leaves to ripen the fruit produced in a canopy that provides an ultimate microclimate ie. not too much shade, not too much sunshine.
This is done by regulating the number of buds left on the mature one year old shoots (now called canes) during the pruning process and the spacing of those canes. The new shoots and their bunches, usually two, come from these buds.
There are three basic categories of pruning: hand, mechanical and minimal.
We will concentrate on the first one here.
The two most common forms of hand pruning are spur and cane.
We spur prune on cordons in our vineyard.

Cordon with Last Season's Canes
A cordon is a permanent vine arm either bi or unilaterally formed off the trunk during the original training process early in the vineyard’s development. On this arm, spaced about a hand’s span apart, are short permanent fruiting units that have been built up over the years by cutting back the canes that form on them, usually two.

Close up of Last Season's Canes
During the pruning process the highest cane of the two is completely removed and the lowest one reduced to two buds or a spur. All other extraneous canes shooting from the arms and trunk are also removed although in some cases the former are used to start new spurs when old ones are not positioned correctly, are too high on the cordon or have become damaged.

Highest Cane Removed
Spur pruning is easy, quick and economical and caters to the growth characteristics of most varieties except those whose basal buds exhibit low fruitfulness.

Lowest Cane Spurred to Two Buds

Completed Spur Pruned Vine
My friend’s vineyard just up the road is cane pruned.
This is a traditional pruning method of Old World vineyards.

Cane Trained Vine Before Pruning
The vines have no permanent cordons, only one (unilateral) or two (bilateral) one year old canes laid along the fruiting wire from the head of the vine which forms on top of the trunk. From these canes, new shoots with fruit emerge during the growing season.

Last Season's Fruiting Cane Removed
At pruning these now two year old canes and its canes are completely removed. A new cane formed from a two bud replacement spur left on the head during the previous year’s pruning is laid down on the wire and cut back to the required number of buds, usually 8-15, depending on the vigour of the vine. The lower cane on this spur is reduced to two buds ready to form a cane and another spur for the following year. All others canes that have formed around the head and trunk are removed.

Next Season's Fruiting Canes Laid
Down with Two Replacement Spurs
Sounds complicated and it can be. Certainly it takes much longer to prune grapevines in this way.
Again most varieties respond well to this form of pruning although those will strong apical dominance (where buds low on the cane tend not to shoot as well as those on the end) can cause problems. This can be overcome by arching the cane when laying it down or spraying with hydrogen cyanamide to promote even budburst.
All the cuttings are collected and piled up for burning later on in the year once they have dried out a little.
I am doing a few thousand cane pruned vines in the other vineyard as well as my own this year and expect to be finished sometime in August.
With climate change well and truly with us, bud burst for the early varieties could expected later that month.
For some updated pruning information (August 2014) click here.

Wednesday, July 04, 2007

Wollemi Pine

In 1994, a NSW National Parks and Wildlife ranger walking in a remote region of the 500,000ha Wollemi National Park in the Blue Mountains west of Sydney came across an unusual stand of trees deep in a sandstone gorge.
Previously only known as a fossil some 90 million years old, he had discovered around 100 mature trees that were to become known as the Wollemi Pine (Wollemia nobilis). One of the world's oldest and rarest trees, the Wollemi pine belongs to the 200 million year old Araucariaceae family which contains the Kauri, Norfolk Island, Hoop, Bunya and Monkey Puzzle pines.

Norfolk Island Pine in our back garden
The Wollemi Pine can grow up to 40 m in the wild with a trunk diameter reaching up to one meter. The bark of the tree is bubbly in appearance and chocolate brown in colour. Each plant has both male and female sexual reproductive cones. These cones appear at the end of branches, the female cone always growing above a male. The Wollemi Pine has two types of branches, one that grows upright looking like a trunk arising in most cases from the base of the tree, and another that grows laterally and bears sessile leaves. One amazing characteristic of the Wollemi Pine is that of every plant growing in the wild has the exact same DNA, making the species even more special.

Our Wollemi pine
The Wollemi pine has been propagated commercially and is now available for general garden and landscaping use.
I was lucky enough to receive one as a present last weekend.
We will keep it as a potted plant for the time being until we decide what pride of place it will take in our garden.