The number of vines you plant and their spacing depends on the way you intend to train them and on the size of your greenhouse. The best time to plant is when the vine is about to start into growth in late winter; alternatively, early autumn is equally suitable. Use strongly rooted, pot-grown vines, preferably about two years old. Dig a hole in the border a little deeper than the depth of the pot and plant the vine, making sure to spread the roots out well. Cover the roots with crumblyand water generously after planting, using tepid water. Make sure the vine is planted at the same depth as it was in the pot.
Place a stake 1.8 m (6’) tall behind the plant, ideally before filling the planting hole, so you do not inadvertently stab the plant’s roots. Immediately after planting, cut the plant back so that two buds are left on a stump which may be 15-30 cm (6-12”) tall. Sometimes the vine will arrive already pruned. If you are training the vine through a hole in the greenhouse wall, cut back enough to leave a length of stem, which has two buds on it, inside the greenhouse.
Methods of training
How to train your vine will be largely decided by the shape of your greenhouse. In a small ridge house, the best method is to plant the vine near the end wall (normally in an outside border) and then train it vertically up the end wall until it is about 45 cm (18”) from the roof. From there train it horizontally along the greenhouse ridge.
You can use this method of training in three-quarter span houses as well, but in these it is more common to plant the vine along the side wall of the house and then train it up the angle of the glass, remembering to keep it about 45 cm (18”) away from the glass. You can train the vine to produce one, two, or occasionally more, main branches, called ‘rods’, each of which is trained up the sloping side of the greenhouse until it almost reaches the ridge.
If you are planting more than one vine, and intend to train just one main branch from each plant, space the vines at 1.5 m (5’) intervals. If you are going to train two main branches; plant the vines at 2.1 m (7’) intervals.
Vines in a lean-to greenhouse can be trained in the same way as those in span houses, unless the vines are sharing the house with other plants, such as a peach or fig tree trained against the back wall. If this is the case, plant the vines at 3 m (10’) intervals and train them horizontally about 60 cm (2’) from the ground.
Supporting the vine
A fully grown vine can be very heavy and must be well supported on strong wires. Whatever method of training you select, the wires should be horizontal, 30 cm (1’) apart, and firmly attached to the greenhouse framework by vine eyes .
Tie young vines to the wires with fillis (soft string) or raffia; older vines can be tied with ordinary string.