Welcome to the top of the crops! Today you will learn about growing french beans in a polytunnel.
French beans or green beans are a wonderful choice for polytunnel growers. They will very much enjoy the warm and relatively dry conditions that a polytunnel can provide.
What is more, the beans will help ensure long-term fertility in the growing areas, by working with bacteria like other legumes to fix atmospheric nitrogen and make it available in the soil. So they make great companion plants for other crops.
Growing French beans is easy even for beginners. But growing them successfully does mean knowing a few key pieces of information that will help you choose the right beans for you, and, of course, position and care for your crop in the right way so they do not fail to grow.
One of the first things you need to understand when choosing french beans to grow is that there are two main types:
climbing beans
and dwarf, or bush beans.
Climbing beans, as the name suggests, grow taller and require support. They take longer to reach the cropping stage but are harvested over a longer period of time.
Dwarf, or bush beans are more compact and don't always need support. They are a good choice for smaller spaces, and grow speedily, but will only be harvested over a few weeks.
French beans are usually grown for their edible pods, eaten as a green vegetable. But there are also varieties that can be grown for shelled beans, which can be dried and used as a pulse. While growing beans for green beans is easier, the latter option is also well worth considering.
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Once you have decided which French beans to grow, the next thing is to decide where you will grow them. You might grow them outside but as mentioned above, they can thrive, and be beneficial, in a polytunnel garden.
Of course, wherever you wish to grow them you need to provide them with the right environmental conditions. They need:
Full sun, and as warm and sheltered a spot as possible. A south or west-facing aspect works well.
Moist yet free draining, fertile soil that is rich in organic matter.
To grow French beans you will need:
French bean seeds or young plants if you prefer.
A suitable growing location in a polytunnel or elsewhere in your garden, either in containers, in raised beds, or in the ground.
Seed trays, pots or soil blocks, potting mix etc. when growing from seed.
Facility to water your crop.
Organic mulch materials.
You can grow French beans from seed relatively easily. This is the cheaper, greener choice and you will have more choice when it comes to varieties. However, you can also if you wish purchase starts from a garden centre or plant nursery and plant these into your chosen growing area if you prefer.
Remember that French beans require the right soil or growing medium to grow well. When you are growing them in the ground or a raised bed, make sure before you begin that the area is rich in organic matter, and free from weeds. Containers can be filled with any reasonably good quality, peat-free potting mix.
Seeds are best sown some time between April and July. When precisely you sow will depend on where you intend to sow. You can either sow indoors earlier in this time period, or directly where they are to grow in the garden once all risk of frost has passed.
Remember that before you sow climbing beans, you will need to think about erecting (or planting) some sort of support.
Common ways to support climbing beans include:
Double rows of canes tied together to form an A-shaped or X-shaped frame.
Wigwams of canes or natural branches tied together at the top.
Growing beans at the base of sweetcorn in the 'three sisters' companion planting combination, along with squash. All three plants work together well, each one benefiting the others and the system as a whole.
Twiggy sticks around the plants can be enough support for smaller dwarf French beans, if any support is required at all.
French beans are sown indoors in mid to late April or early May. Sow the seeds into their own small pots or soil blocks, or use small, deep modules with one seed in each one. The seeds should be sown to a depth of around 5cm.
Place the seeds on a sunny windowsill or in a propagator to germinate. They should germinate within a couple of weeks. Seedings will grow fast in warm and bright conditions and you will need to make sure that you keep their growing medium moist with regular watering.
Sowing in the ground is often problematic in the UK, germination rates can vary and pests may eat the seeds before they get the chance to germinate.
But if you prefer, you can direct sow into a prepared area, with any supports required already in place, once the soil begins to warm, usually towards the end of May or June.
Sow the seeds around 5cm deep, and around 15cm apart. With climbing beans, you can sow a couple at the base of each cane of the support structure, then thin to leave just the strongest seedling at each station.
Dwarf beans can work well sown in double rows or blocks so they can support one another. So that you can harvest dwarf beans over a longer period, you can consider successional sowing this crop from late spring through to mid-late summer.
If you choose to sow into a container in which the plants will remain throughout their life cycle, then choose one of sufficient size.
Dwarf beans need a container at least 35-45cm deep and wide. Climbing beans need a container that is 45cm deep and ideally 75cm wide, and heavy enough that it will not tip over with these tall plants as they grow.
Whether you are planting out indoors sown seedlings, or purchased starts, make sure that you do not plant out too early. And ensure that you harden off the plants before you place them into their final growing positions.
Aim for an approximate spacing of around 15cm between the plants. With climbing beans, it is a good idea to tie the plant loosely to the support to get them started with twining up the structure.
If you are trying for the three sisters planting plan, the sweetcorn should be planted early to give it a head start and make sure that it is strong and mature enough to support the climbing beans over the rest of the growing season.
Remember that there are also other beneficial companion planting combinations, so when planting out your beans you should also always think about what else is planted or will be planted close by.
Caring for French beans is not too challenging as long as you have chosen the right growing location.
One of the main things to think about when growing French beans is watering. While these plants can be quite tolerant of dry conditions, they will provide the best yields when they receive consistent water throughout the growing season.
So make sure that you water well, especially when growing in containers, which will dry out more quickly. When growing in a polytunnel, the right irrigation system can improve your yields.
But take care not to overwater, avoid waterlogging and make sure excess water can always drain away freely.
Weeding can be important when growing French beans to get rid of unwanted competition for water and nutrients and to ensure good airflow to prevent or reduce the chances of certain diseases and other issues.
A good quality organic mulch of well-rotted manure or compost helps retain moisture in the soil, and helps suppress weeds to a degree. Mulch around your beans upon planting, and replenish this mulch to protect and improve the soil over the summer months.
Since these are self-pollinating, collected seeds should come true, meaning that you will end up with plants like the parent plant if you sow these for next year. Seeds can easily be left until the end of the season to mature fully on the plant, then dried and stored over winter to sow in spring.
When climbing beans reach the tops of the supports you have erected for them, cut off the growing tips. This should encourage bushiness lower down and stop the plants becoming top heavy. It will also ensure that you can reach easily to harvest the beans. Beans that straggle and loosen from their supports can be tied in to provide them with a little assistance.
As mentioned above, beans are usually picked as a green vegetable and we eat the pods while they are green and young. If harvesting green beans, pick the pods from when they are around 10cm long.
Pick them regularly and more will be produced. Remember that climbing beans will crop over a much longer period of time than dwarf varieties. The pods when they are ready should snap easily, but individual beans inside should not yet be visible through the pod.
Remember however that there are also some types that you will leave to mature and from which you will not harvest the pods but the beans inside, for fresh eating or, more usually, for drying and for use as a pulse.
French green beans will only keep in your fridge for a few days, but you can also blanch and freeze them for use within 6-8 months. If you have a pressure canner you can also safely pressure can your beans to preserve them for use over the winter months.
French bean varieties that are excellent choices for UK growers include:
Climbing French bean varieties:
‘Algarve’
‘Cobra’
‘Eva’
‘Golden Gate’
‘Hunter’
‘Limka’
‘Musica’
‘Pantheon’
And dwarf French bean varieties:
‘Annabel’
‘Boston’
‘Dior’
‘Elba’
‘Marona’
‘Nomad’
‘Sprite’
‘Stanley’
‘Tasman’
All of the above have an award of garden merit from the RHS.
Timings are important because cold conditions can kill or stunt French beans and reduce yields. Lack of water can cause a range of issues. Other than these things, pests like aphids, slugs and snails can cause issues. Companion planting and integrated organic pest management are the answers.
Vertical growing can be beneficial, allowing more to be grown in small spaces, so do not discount climbing beans too easily even in a small polytunnel.
Companion plant for beans with nasturtiums or other options as trap crops for aphids. And use beans widely as companion plants for their nitrogen fixation.
Remember, rotating bean crops throughout the different growing spaces in your polytunnel garden will help ensure long-term fertility.
