Most plants get along fine with runner beans, but a few hold them back. With good runner bean companion planting, you keep those few troublemakers away and let the rest of the garden help. The short list of plants to avoid near beans starts with the onion family. Onions, garlic, chives, and leeks all belong to the same group, and gardeners have long reported that they slow bean growth when planted close. So the first rule is simple. Keep your beans well clear of the onion patch.
No one has fully pinned down why the onion family causes trouble. But the same pattern shows up again and again, in old garden lore and modern beds alike. These plants are called alliums, and the group covers onions, garlic, chives, leeks, and shallots. Plant them next to beans and the beans tend to grow weaker and set fewer pods. You do not need a science lab to dodge this one. Just give the two crops their own corners of the garden and they each do better apart.
There is a second problem that has nothing to do with the onion family. Runner beans are tall, fast climbers that can top 8 feet (2.4 m) in a single season. That wall of leaves throws heavy shade. Any short, sun-loving crop planted right at the base of the vines pays the price. Think peppers, bush tomatoes, or low salad greens that need full sun to crop well. They end up sitting in the shadow of the beans for most of the day and never fill out the way they should.
The fix for shade is easy once you think about the sun. Put low, sun-hungry crops on the south side of the bean teepee or trellis, never tucked behind it on the north side. That way the beans cast their shadow onto a path or a taller crop instead of onto the plants that need the light. You can also run a row of beans along the north edge of a bed so the tall vines never block the sun from anything growing in front of them.
Now for the good news, because the list of friends is much longer than the list of foes. The classic example is the Three Sisters, an old planting method that grows beans with corn and squash together. The corn gives the beans a living pole to climb, the beans help feed the soil, and the squash sprawls low to shade out weeds. The University of Arkansas Extension points to this trio as a proven pairing. Beans clearly have plenty of welcome neighbors.
Among the best scarlet runner bean companions are nasturtiums, which earn their spot by working as a trap crop. Aphids swarm to the nasturtiums and leave the beans alone, so you draw the pests off and protect the harvest. Plant a few near the base of the vines and let them take the hit. Corn, squash, and nasturtiums all make strong neighbors, and none of them fight your beans for light or soil the way the onion family does.
So the answer comes down to two short rules. Keep your runner beans away from anything in the onion family. And do not let the tall vines shade short crops that need full sun. Site the beans on the north edge of the bed, put sun-lovers out in front, and lean on corn, squash, and nasturtiums as good company. Do that and your beans climb strong while the rest of the garden grows right alongside them.
Read the full article: Scarlet Runner Bean Growing Guide
