As the weather patterns change and if we experience long warm summers as we are told to expect, it is tempting to have a go at growing a grapevine. Many years ago I grew a grapevine at the side of our garage with limited success. It was fun to watch it grow until it eventually covered the whole side of the old wooden garage.
I am sorry to say it had no fruit that was edible and it went into the skip when we build our new brick garage. It is almost impossible to grow a good desert grape outside this far north. However, it is well worth growing for its autumn colour, the leaves turning red and purple from September onwards giving a most spectacular effect.
It is not unusual for a vine planted on a southfacing wall to eventually reach a height and spread of 10 to 15 ft. If you visit old gardens you very often find lean-to greenhouses against the white washed south facing wall of a walled garden. In the greenhouse wall is what looks like bridge holes. These are because it is best for the vine to be planted with its roots outside and the stem and all the top growth trained through these bridge holes into the greenhouse on wires into the roof inside. This offers warm frost protection, easy maintenance and training.
Having the roots outside means that the plant is not restricted and has a good root run, enabling them to receive more water and fertiliser than is possible if planted inside. The old gardener used to heap barrow loads of horse manure on the roots every winter to protect from frost and to rot down, thus feeding the roots.
Grapes are an ideal conservatory plant if trained on wires across the roof. Their large leaves will give shade in the summer and during the winter with no leaves it will let in the winter sun.
Another way to train a grape vine is on a trellis-type frame attached to a south facing wall of the conservatory. During the first season only allow one strong stem to grow, cutting out all others when the plant has discarded all its leaves and in a dormant state, usually December or early January.
Cut back to approximately two thirds of its height, the following years laterals (branches) are produced and these should be pruned back in the summer leaving five leaves, then come December prune again to two buds. Grapes should be produced in this second year.
Thin the bunches leaving only the largest and strongest on the plant. As the fruit develops, cut out the smallest of the grapes with a pair of small scissors so as to make room for the remaining fruit to swell. To protect these bunches from disease and pests try placing them in a clear plastic bag, tying the neck of the bag with string around the stem of the bunch.
If you have a sheltered patio, it is worth trying to grow a grape vine in a pot supported by a frame. Treat in exactly the same way as described above but make sure that the pot is large enough, at least 16" and has adequate drainage. Stand on some stones or pot feet to lift the pot off the slabs. Use a loam based compost such as John Innes no. 3, feed with a liquid fertiliser at every watering and never let it dry out.
To over-winter place it in a frost free shed or greenhouse. As I have said before, the autumn colours are stunning and if you have fruit then that is an added bonus and a barbeque talking point.
I can remember friends of my parents who lived on Chester Road, Streetly, they had a lovely old vine in their conservatory. It gave excellent fruit every year, the only drawback was collecting up the leaves in the autumn. However, the end result justified all their hard work of training and pruning.