Your grapevine can become wild if you skip winter pruning even once, and after a few years the neglect will be devastating. Even vines which have been pruned incorrectly are easier to restore and bring back to fruiting than non-pruned ones! However, you may salvage a neglected vine with some rigorous restoration pruning (thinning out).
A vine can be old and gnarled with have thick, entangled stems and still be perfectly healthy. The branches are then close to the wall, the plant has lush foliage and is often green down to its base (Image 01); leaves and grapes are healthy.
Not so in Image 02: A neglected vine on a façade has an abundance of branches with weak shoots and diseased leaves. Occasionally, there is also a lot of deadwood amongst the branches. Foliage is usually sparse, the plant grows away from the wall, and most of the greenery is at the top of the plant.
This question depends on whether the plant is infected with mildew. The expert can also identify this disease in winter by the dried up berries, which usually remain on some grape bunches. Split berries with the seeds showing through are an unmistakable sign of severe mildew infection. Lilac coloured, reticulate to patchy discolourations on the usually light-brown canes from the previous year also indicate mildew.
Mildew can also affect a usually robust and even fungus-tolerant grapevine if it has been neglected; however, this alone does not necessarily require removal of the vine. Today however, there are plenty of new, fungus-tolerant varieties, which may be neglected for some time... their entangled canes become a headache only after a few years... but if the vine is healthy, it is definitely better to keep it than to plant a new one.
However, if a vine combines all the above symptoms with low vigour and mildew as illustrated in Image 02, the vine cannot be rescued without professional spraying and it is better to remove the entire plant.
If the vine is to be kept, the first step is to pre-prune the main framework- either by shortening the thick stems or, depending on the overall shape (fan form), cutting them off completely. Next, many of the remaining thinner shoots are removed. In the end there will be some well lignified canes from the previous year - recognised by their light brown, grey-brown, or brown-red colouring - arising from the stems at about 15-60cm apart. These shoots are later trained to new side shoot positions; therefore, they should arise directly from or as close as possible to the framework, the most suitable being the water shoots from the previous year. Of these shoots, the more basal ones are usually pruned shorter (spur pruning and rod pruning), the upper ones a bit longer (rod and cane pruning or arched cane pruning).
If there are no previous year's canes arising from the stems and only the main framework remains, then new shoots will grow from dormant eyes, as happens in vine renewal.
Training of the canes can now be done according to the desired form- usually and initially in the free fan form (Image 03). This is followed by tying. All new shoots with more than 4-6 eyes are then tied horizontally- if this is possible without breaking off the shoots. Tying them this way will ensure an even bud burst. In the following years the new side shoots are further trained according to the desired form.