Recommended varieties: Cobra.
You can sow climbing french beans indoors from the middle of May to plant out later or sow outdoors at the end of May. Be aware that French Beans hate windy cold sites so unless you have a warm south facing sheltered garden you are better off growing runner beans or dwarf French beans.
Sow the beans towards the end of May in 9cm pots. Plant five seeds in each pot about 4cm deep using fine seed compost. Water and leave in the greenhouse or polytunnel to germinate. There should be no need for a heat bench or propagator this time of year. The seeds should germinate in 7 - 14 days and will grow quickly. Bear in mind for each wigwam support you'll need 30 seedlings so you'll need to plant 5 trays.
Build a cane support for your beans. Plant 5 seeds around each pole of your climbing frame. The planting date will vary but the safest time to plant is late May till June. French beans will need a minimum soil temperature of 12° C.
Hardening Off Climbing French Bean
Plants that have been raised indoors will need to get used to the outdoor temperature and conditions before they can be planted outside, this will take about a week to 10 days depending on the weather. French beans hate the cold and are likely to suffer shock so make sure you do this.
The best way is to use a cloche or mini greenhouse. You can leave the cloche off the plants on dry frost free days and replace at night. Gradually increase the time with the cloche removed until the end of the week when you leave it off day and night.
If the weather is mild you may not need the cloche, just move the plants outside for longer periods each day.
If you have started your seeds on a windowsill you will need to leave them in an unheated room for a day or two before moving outside to the cloche.
Direct Sowing French Bean Outside
French beans can be direct sown outside towards the end of May. It is possible to start them off earlier if you have a more southerly garden, I'm keeping on the safe side.
Build a 'wigwam' support from bamboo canes. Get the longest bamboos you can as french beans are tall growing plants, I would go at least 8 foot. Make your pole ends about 40cm apart.
Plant 5 seeds around each pole in your climbing frame. Sow at a 4 cm depth, cover and water well. The seeds should germinate in 7 - 14 days. You will be planting approx 30 seeds around each support.
If a late frost is forecast cover the germinating seedlings with a layer of fleece.
One you've hardened off your bean seedlings they are ready to be planted out in the garden. Choose a warm sheltered as French Beans hate exposed sites.
Build a crop support (see direct sowing) and sow 5 seedlings around the base of each bamboo cane. There is no need to separate the seedlings in the pot, just plant them in a bunch as they come out. Water well.
Climbing French Bean Care
Slugs can be very problematic especially when plants are young. Use an organic slug pellet or beer trap. Apparently slugs love bran so leaving bran piles around the garden will attract them in their droves. You can collect them and throw them over your neighbours wall.
It is said they gorge themselves so much they explode but I can't say I've ever witnessed this particular spectacle.
Black bean aphid (Blackfly) can be problem in July and August. You can spray with the natural insecticide 'Pyrethrum' or wash off with a strong jet of water. Growing marigolds near beans can help as they attract beneficial insects like ladybirds who love to eat blackfly.
Downy Mildew and foot rot can be a problem but with good crop rotation this can easily be controlled.
Keep the area around the seedlings weed free and aerated with regular hoeing. An oscillating hoe is the easiest and most satisfying tool fro hand weeding.
You can harvest your Climbing French Beans from July until the first frost. It's important to pick your pods regularly (at least once or twice a week) to get the tenderest beans. Many people are put off runner and French beans from eating beans which have grown too big and stringy.
If you don't keep harvesting the plant will put all its energy into ripening the seeds rather than producing fresh, new beans for you to eat.
Even if you can't face another bean keep picking otherwise the plant will stop producing for the season. If you let just one or two beans ripen the plant will shut down production.
You will have a glut of beans at some stage so read up on how to store them, give them away, compost them, whatever, just keep picking!