While it is relatively easy to grow raspberries outside in the UK, the vicissitudes of the weather here mean that some years, the crop will be much better than others. Commercial raspberry growers will often use a polytunnel to ensure the quality and reliability of their crop and home growers could also grow some raspberries in a polytunnel. Raspberries grown in a polytunnel can help to make the most of the vertical space and can make it easier to get a good, reliable crop of this delicious fruit.
Raspberries are usually grown from bare-root canes acquired during the dormant season, between late autumn and very early spring. These bare root canes should be planted into their final growing position as soon as possible after you get them. When choosing your raspberries, you will need to decide whether you would like summer-fruiting or autumn-fruiting varieties. Some raspberries are primocane (fruiting on this year's growth) while others fruit on the growth of the previous year. Researching varieties will also allow you to get the right option or options for your area. With enough space and the right varieties, you could be eating raspberries all the way from June through to October.
Before you plant your raspberry canes, you should consider what sort of support you will provide for your raspberries. Most commonly, a frame is built and your raspberries are tied into wires on that frame. However, when space is limited, you can even use a single post to which to tie a few raspberry canes.
Your bare-root canes may not look like much initially but soon they will burst into life. You may also see some suckers – remove any that grow where you do not want them and any that make your raspberry patch too crowded, as crowded conditions can encourage mould or fungal problems.
It is a good idea to prune raspberries on a yearly basis to keep them healthy and productive. Cut back summer fruiting canes that have fruited directly after harvesting the fruits, leaving first year canes to fruit the following year. With autumn fruiting varieties, simply cut back all the growth to ground level in late winter.
Make sure you give your raspberries plenty of water throughout the growing season. Water at the base of the plants. A mulch can help to keep in soil moisture and a good, organic mulch will also help to feed your plants.
In a polytunnel, you can protect your crop from birds, which can eat the fruits before you get to them when you are growing them outside.
Harvest raspberries when they are fully coloured (usually red, though there are also yellow and other varieties) and slip easily off the rasp. Raspberries can be eaten fresh, cooked in a range of recipes, preserved in jams or frozen for later use.