I believe beans (winged beans or winged peas as they are called) are medium rooting depth --> that is 18" to 24". You can go online and search for rooting depth of vegetables and you'll get a table that shows: very shallow, shallow, medium, deep and, very deep rooted vegetables. Where very shallow is under 12" , shallow: 12"-18", medium 18"-24", deep 24"-36", very deep 36+". This is also what they call the EFFECTIVE root zone -- so in reality the plant can go deeper. Tomatoes are deep or very deep rooted (and tend toward the 36+" side) -- but many people grow them in containers that are about 18" deep -- the growth is a bit stunted, but other than that they look fine. So when you see that beans like about 24" of depth, that does not mean you can't successfully grow them in a 15" deep pot. I have found that VOLUME of soil is more important than total depth (it's a bit of a give and take) -- but lets say a 10" deep half barrel would be better suited for winged beans than a 24" deep narrow fluted container. Plants sent out roots to collect the necessities of life; water, macro nutrients (N, P, K, calcium etc.) and micronutrients (boron, iron, zinc etc.) - the roots also provide stability. Beans fix their own nitrogen but still need all the other nutrients and I have found benefit greatly from an application of micro nutrients. Whatever container size or shape you choose you need to ensure all the necessities of life are available for the plant; good aeration in the soil (look at orchid pots if you want to understand really good aeration), enough water, nutrients in a timely fashion. A small pot with little soil volume will need to have nutrition added regularly, as the plant will quickly use up all the supplies available in the soil. Further, I have found that pots with a lot of surface area give me plenty of room to top up the plant with compost or manure -- if you don't have room to top up the soil you need to use liquid fertilizers (like making you own leachate - or buying some commercial fertilizers). I remember when I wanted a container garden (my first ever container garden in the city - having always planted plants directly in the soil as containers tend to be expensive) -- anyhow, I learned the hard way HOW FAST the nutrients get used up in containers -- containers tend to require a lot of amendments (fertilizer) compared to plants in the soil for two reasons: 1. plants in the soil can send their roots out further scooping up nutrients, and using what is already there -- like minerals from rocks 2. nutrients tend to also LEACH out of containers when you water; and you are less likely to leach out your nutrients even in raised beds as you need have "run off" to do so. Hope this helps with your decision on size and shape of your pot !!!

- Celeste Archer