Grapes can feel like quite a luxury. Thanks to our changing climate, wine can be grown further north than at various points in history, but many of us in the UK will still fail to get a reliable crop unless we grow them under cover. A polytunnel can be the perfect place to grow your own vines, providing just enough extra warmth to keep the plant grapes happy and allow them to ripen well. In fact, you will usually find that just one vine is enough for indoors planting in a polytunnel or greenhouse, unless it is a particularly large one.
Buy your small grape plant and place it in a well-prepared bed of good quality soil containing plenty of well-rotted compost between early autumn and early spring. You can consider placing the roots of the grape vine outside the tunnel and training a stem in from outside. If you do plant inside the tunnel, remember that this will increase the irrigation required. Prepare a structure for your grape vine to climb on. Over the first summer train one single stem and then during the first winter, cut it back to around 45cm above the ground. You can then gradually shape the vine. Make sure you keep on top of cutting back side shoots, as these could easily do some damage to polytunnel plastic if you do not take care.
Grape vines are an investment in time and space. Be patient as it will take several years for your vine to begin producing a worthwhile grape harvest and mature grape vines take up quite a lot of space. However, investing that space and time could definitely be worth it. A polytunnel with a dangling vine and grapes can really be a lush and magical place – a grape vine will certainly allow you to make the most of the top area of your polytunnel and could provide some useful shade in the summer months.
It is important to keep grapes will watered but not waterlogged and yet the humidity should not be too high or grapes can be prone to rotting on the vine. Open the polytunnel doors wide on hot, humid summer's days to make sure humidity inside the tunnel does not rise too high. Mulch around the roots well to help retain moisture and feed with high potash organic fertilisers from when growth starts through to when fruits start to ripen.
When your vine begins to produce lots of grapes, you may be reticent to get rid of any of the growing fruits at all. It is important, however, to thin grapes ruthlessly while they are very small. Thin out berries in the centre that are too crowded to leave space for the others to grow. Try not to touch the bunch as this will ruin the bloom on the grapes.
Simply harvest your grapes by cutting bunches from the vine and use them for either eating, if they are dessert grapes, or for wine.