Welcome to Top of the Crops. Today, you will learn about growing raspberries in a polytunnel for UK gardening! We will cover everything, from where to grow, how to grow, planting, harvesting, recipes, and more. And for further gardening tips, check out our blog Polytunnel Gardening.
Raspberries are one of the most delicious fruits around and one of the best and easiest berries to grow in your garden. Whether they are grown in a polytunnel, a fruit cage, or elsewhere in your garden, these are great value plants that can deliver fantastic yields.
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Raspberries, usually Rubus idaeus, though sometimes other species in the Rubus genus, are fruiting plants particularly popular with UK gardeners. There are many different raspberry varieties to choose from that provide an abundance of berries on fruiting canes in the summer or autumn months.
Raspberries are remarkably easy to grow and low-maintenance plants, perfect for those who want to grow more food with less effort and time.
The most important things to remember about raspberries when it comes to their placement is that they need:
Full sun or light, dappled shade.
A fertile, humus-rich soil that is moist yet well drained and neutral to slightly acidic.
To grow raspberries, you will need:
Raspberry canes (either bare root or pot grown plants can be purchased).
A suitable growing location that will meet the needs of the plants.
Organic matter to use as mulch around your raspberries.
Gardening gloves.
A spade for planting.
Pruning tools.
Usually – a support structure of some kind. (More on this below).
Raspberries can be grown in dedicated beds within a polytunnel or fruit cage. They can also be integrated into your garden, becoming parts of mixed polyculture planting schemes such as fruit tree guilds or forest gardens.
Raspberries might be integrated into the overall design for a garden, becoming part of edible fruiting hedgerows, or used to separate different 'garden rooms'.
As long as the location you are considering meets the basic growing requirements of the plants, there are many different options to consider when it comes to choosing precisely where and how to grow raspberries on your property.
Raspberries can be purchased either as bare-root plants over the dormant period, or as pot grown plants. There are numerous varieties available from garden centres, plant nurseries and online vendors.
If you select the right varieties then you can potentially be harvesting raspberries over a long period of time, from early to mid summer right through until autumn.
Once you have chosen a suitable planting location that provides the conditions that raspberries need, you should prepare that site, clearing any weeds, and adding organic matter. Raspberries will do best in the ground but it is also possible to plant in containers (see below).
The ideal time for planting is the autumn, but you can also plant throughout the dormant period, any time before around March when the soil is not frozen or waterlogged. Raised beds are useful to improve drainage – and you should consider growing raspberries in a raised bed if you have heavy clay soil.
Raspberries are usually grown in rows, and these should ideally run north to south so all the plants get as much sun as possible.
They will usually need some form of support (unless you are growing more unusual groundcover raspberries rather than the usual forms with more upright canes). Supports should be in place before planting. We cover some of your options a little later in this guide.
Raspberries should be placed around 45-60cm apart, with 1.8m between rows. When planting, make sure you do not dig too deep a planting hole. The roots of the plant that are highest in the ground should be no more than 5cm below the surface of the soil.
After planting, mulch well with a 7.5cm thick layer of organic matter. Most raspberries will also be pruned immediately after planting to leave around 25cm above the ground.
The only exception is for summer-fruiting raspberries bought as 'long canes' which should be left or you will lose the fruits for the year.
If space is limited, raspberries can as mentioned above be grown in containers. The container should have good drainage at the base and be at least 38-40cm wide.
Fill the container with a potting mix that is peat-free, and ideally soil-based at least in part. Again, make sure the plant sits at the same level by checking the soil mark on the stem.
Caring for raspberries is generally very easy and straightforward. These are not usually plants that will take up much of your time, though they will require a little more care if they are grown in containers.
Raspberries do need consistent moisture throughout the growing season, so it is important to take care of this and provide water consistently during dry spells, especially during the time when raspberries are flowering and setting fruit.
Make sure the water is delivered to the roots within the soil and try not to wet the foliage, flowers or berries to reduce the risk of fungal infections. And remember that plants in pots will usually need to be watered more frequently.
Use rainwater to water raspberries wherever possible, especially in hard water areas.
After planting raspberries, add a mulch of organic matter around their bases that is around 7.5cm deep, but make sure you leave a gap around the base of the stems to avoid issues. Replenish this organic mulch each early spring to conserve soil moisture and reduce weed growth.
In addition to mulching plants in the ground in early spring, it may be a good idea to feed with blood, fish and bone or another organic potassium-rich fertilizer. Plants in containers will need more feeding, and will benefit from feeding once a month with a potassium-rich, organic liquid plant feed throughout the growing season.
Deciding how to support raspberry plants is an important decision to make when growing raspberries in a formal setting in your garden. While raspberries can be left to grow more wildly and allowed to sprawl in a more natural setting, supports make care and harvesting a whole lot easier.
Three main options are usually recommended. These are:
Two tall posts around 1.8m tall, with further posts if rows are very long every 3.6m or so, with three lengths of strong wire string between them at 60cm intervals.
This is a good method for summer-fruiting raspberries. Their fruiting canes can be tied in along one side, while the new stems for the following year's fruit go on the other. This makes pruning easier later.
Two posts around 1.8m tall for summer raspberries, 60cm tall for autumn-fruiting types, again with extra posts every 3.6m or so if necessary. These posts should have short lengths of timber attached to the top of each post, and another 60cm below for summer-fruiting raspberries.
To the ends of these cross-timbers, strong wires should be run to create parallel wires along each side of the raspberry row. Plants are not tied in as they are supported by wires on both sides.
Alternatively, you can make a double fence, with posts and wire along both sides of the row of raspberry plants.
This system works well for autumn-fruiting raspberries or summer-fruiting ones in a tighter space.
If you do not have much space, or are growing in pots, single raspberry plants (sometimes up to three or so) can be tied in to a single sturdy post. The post will typically need to be around 60cm tall for autumn-fruiting raspberries and 1.8m tall for summer-fruiting ones.
You can also tie raspberry plants into a wigwam form support of canes or branches if you have a limited amount of space.
Pruning raspberries is something that some may find confusing at first. However, as long as you understand which type of raspberries you are growing it is actually relatively simple.
The key thing to remember is that summer-fruiting raspberries produce fruit on second-year stems (floricanes) while autumn-fruiting raspberries fruit on the current season's growth (primocanes). This means they are pruned in different ways.
After harvesting the raspberries from these types, cut all the stems that have borne fruit down to ground level. Select the strongest and best new green canes that will fruit the following year and tie these in to your supports.
Unwanted new canes can be cut to ground level and, where necessary, young stems taller than the top wires of your support structure can be cut back to a bud around 10cm above the top wire in February.
These raspberries are pruned in February and all old, fruited stems are usually removed to ground level. New ones will grow in the spring.
Alternatively, you can cut just some to the ground and some just below the top part where fruits formed. The idea is that the stems left taller will fruit in summer, while those cut right to the ground will fruit later – giving double cropping. Only some varieties are suitable for this treatment, however, and yields are not always that great.
The only other potential pruning required is, in early summer, pruning to remove weaker stems from any clumps that have become congested. Though this is not always required.
With all raspberries, you may also wish to remove or transplant suckers that form in spring outside the intended bed or growing area.
Raspberries can easily be propagated simply by transplanting suckers to new areas of your garden. Large clumps can also be divided.
It is best only to propagate from recently purchased plants that are free from disease as older plants may often have issues that can infect new plants and impact their health and the yields that they provide.
You can typically expect to harvest summer-fruiting raspberries between June and September, depending on the variety. Autumn-fruiting raspberries are generally harvested between mid August and the first frosts.
Check plants and harvest regularly, and you can be picking raspberries over a relatively long period. It is best to pick on a dry and sunny day where possible as damp berries are quicker to mould.
Of course, raspberries can be eaten fresh, or used in a range of recipes. You should find plenty of ways to use raspberries on your property.
Fresh raspberries are best eaten straight from the plant. But they will store in your fridge for a few days and can also be frozen for later use. You can also use raspberries to make a range of preserves like raspberry jam, for example, to enjoy over the rest of the year.
There are many good varieties of raspberries to grow in the UK. Check out that link for some suggestions.
One of the main issues when growing raspberries is birds and other wildlife getting the berries before you get the chance to harvest. Protecting your plants with a fruit cage or growing them in a polytunnel can help reduce losses.
Raspberries are often healthy and vigorous plants, and tend to crop well when the location is wisely chosen. However, they can get various viruses and fungal diseases including cane blight, spur blight, and rust.
Viruses can cause stunting and distortion and plants affected should be removed quickly or the problem can spread through aphids and other sap-suckers.
Insects can occasionally become an issue – such as raspberry beetles, and leaf and bud mites can sometimes also be seen. Magnesium deficiencies can arise too, and turn the leaves yellow or reddish brown between the veins.
Growing raspberries in a polytunnel or fruit cage helps keep them safe from pests to a degree. But make sure pollinators and other beneficial wildlife can access the area.
Companion plant for pest control, pollinator attraction and other benefits but don't plant too close to raspberries as they will not appreciate the competition.
BBC Good Food. (n.d.) Raspberry Recipes. BBC Good Food. [online] Available at: https://www.bbcgoodfood.com/recipes/collection/raspberry-recipes [accessed 15/12/23]
