Not So Sour Grapes

A generation ago you would have to be a good gardener indeed if you were to keep a grape vine. Today they are commonplace, if you stick to the rules, says Paul Peacock.

A polytunnel is probably the ideal place to grow grapes, especially in the cooler north of the country. Many farmers are successfully growing commercial stock in the UK; mostly all converted into wine of ever-increasing quality.

Varieties

At one time the only vine available was the Black Hamburgh, which gave a lot of smallish fruit that were reasonably sweet. The novelty of having grapes at all made them taste a little sweeter. But there are now a large number of varieties available and you can not only grow good eating fruit, but also get a good approximation of some of the world’s favourite wine grapes.

Planting

There are a number of traditions about growing grapes indoors. Firstly, the root is planted outside a greenhouse and the vine is trained through a window inside. The other method is to grow a vine in a hole, half-filled with a dead sheep!

The extra space in a polytunnel however, makes it possible to plant the vines in bush form, as though they were outside in a vineyard. We shall concentrate on the old-fashioned greenhouse method, growing the plant as a cordon outside the tunnel/greenhouse.

No dead sheep?

Should the recommended dead animal not be available, dig a hole 60cm deep and at least twice as wide as the root ball. Keep the dug soil and mix half of it with an equal amount of compost.

Tease out the roots and place onto the manure, filling in with the soil/compost mix. Firm well, using as much soil as you can fit into the space. Cover the base of the plant with a good layer of compost as mulch.

Initially it’ll be important to stake the vine (for the first year), allowing it to grow and become established. It can be supported inside the tunnel on an end brace or a specially erected pole.

Vines create a lot of shade and are best in full sun. Tomatoes don’t make good bedfellows with vines because of their height, and the evaporation from the tomato creates an atmosphere that tends to promote fungal infections.

Training

There are dozens of systems for growing grapes, and some rather complicated books on the subject, beyond the scope of the space we have available here. Readers should try Successful Grape Growing for Eating and Wine-making by Alan Rowe.

Perhaps the commonest and easiest method, worth explaining here, is the cordon system. Training your vine at a little higher than head height, tied to firm supports will produce a strong vine. You will need to consider erecting something more than just the hoops of the polytunnel, which are usually too far apart as an effective support. You will have something like a system of wires at 30cm intervals. Each of these wires will support a lateral, which will bear fruit. The ‘leader’ will run at 90° to these wires.

In the first two years don’t allow any fruit to form on the plant. You’re simply building the structure of the plant. In year one, choose the leader branch and tie/support it until it reaches the wires. Any sub laterals should be plucked out entirely.

In the winter, collect the fallen leaves, and cut the leader back to where it’s at least as thick as a pencil, cutting just after a bud.

Repeat this in the second year, then from the third year you can train a lateral for each of the wires. Remember, grapes appear only on new wood, so each year you need to prune the lateral ‘cordon’ canes back to about 10 buds (or you can use more short 3-bud spurs).

Problems

People allow too much fruit to develop and then wonder why they are all covered with Botrytis. The keyword is ventilation. Cut out bunches of grapes that fall near each other, leaving plenty of space for air to remove humidity. Fungal infections thrive when the humidity and temperature is high.

Mildew and Botrytis are controlled with copper-based fungicide. Bordeaux Mixture was invented 150 years ago by monks to treat vines in France, and has been on the organic list for many years. Not now strictly thought of as organic, many gardeners still use it.

An alternative is to grow one of the less susceptible varieties and keep the humidity low and the grapes widely spaced – at least no more than 18 bunches to a mature plant.

Jargon Buster

LEADER (also known as a ‘rod’) is the main stem of the plant. Water shoots come off the leader, low down the stock. Remove these.
LATERALS grow from the leader’s nodes.
SUB LATERALS grow from the laterals.

Some Common Varieties

These varieties are easily available and grown in the UK. You can grow almost any variety under cover, although it’s best to choose the late-ripening ones. There are scores more!
BACCHUS - A German white variety that gives excellent juice.
SIEGERREBE - A very early maturing variety, bred from Gewürtztraminer, producing delicious brownish grapes.
SCHÖNBURGER - Grown particularly in Kent, a good flavoured grape with lots of sugar.
SEYVAL BLANC - Grown a lot in the USA, small white fruit, heavy cropping, now used mainly for sparkling wine.
MADELEINE ANGEVINE - A citrus flavour, ideal for cool climates, early ripening and a very reliable cropper.
BLACK HAMBURGH - The original gardener’s grape – fantastic for lots of good fruit, if grown under cover.
TRIOMPHE D’ALSACE - Like blackcurrants, good sweetness and very reliable, slightly foxy flavour.
PINOT NOIR - Just to show you can grow one of the classic varieties. Susceptibility to Botrytis can be a problem.

The full as printed magazine article can be viewed here...