Giant beans are really easy to grow and have the potental to reach a yard long, hence their nickname "yard-long beans."
These giant beans originated in China and can often be found for sale in the produce department of Asian Supermarkets. I got started with growing these giant beans when I bought up a whole bunch of seed packets filled with Asparagus beans in the gift shop of a Ripley's Believe it or Not museum on clearance for 5 cents each. I had much success growing these large beans, and eventually expanded to other variates of giant beans, and have been growing them ever since.
In this Instructable, I will show you the basics of how I grow my beans.
Step 1: Obtain the Seeds...
In order to grow giant beans, you need to pick out a variety that grows to an exceptionally large size. The two types of giant beans that I have had the most success with are Yard Long Asparagus Beans and Red Noodle Beans.
I personally have never purchased from them, but it seems Kitazawa Seed has a good selection of giant beans.
The seeds I used were from the clearance of a Ripley's Believe it or Not museum gift shop (5 cents per packet) and also from Territorial Seed Company. Chances are you won't find these beans in the seed department of your local Home Depot, so the internet is probably your best bet for buying seeds.
Step 2: Make a Trellis
These beans need to climb in order to grow to full size. Solve this problem by building them a trellis.
Find a type of wood that you have readily available. I used the stems that hold up palm fronds. If you have the right type of palm tree, these grow to about 5 or 6 feet and get really strong once dry. Cut them off the tree and remove the fronds, leaving the straight wooden sticks.
Take two cut branches and form a triangular shape with them. Nail/screw the two branches to one another, and repeat with two more branches (try to keep the two triangular shapes at the same angle. Go outside in your garden, and bury the two loose ends of each assembled unit at least six inches into the ground. Finally, take a fifth branch and attach it to the top of the two triangular end pieces.
Next, wrap a horizontal length of string around the perimeter of the bottom of the trellis. Wrap the string around a few times and tie it off at each branch to make it nice and taught. Use more string to tie vertical sections from the bottom horizontal string to the horizontal wood at the top of the trellis. Repeat this until the whole trellis is has vertical strings every few inches.
If you have a chain link fence, this whole trellis can be skipped. Plant your seeds along the fence and the beans will climb the fence with no problem. If you have a wooden fence, add nails/screws every so often and attach strings to these, and your beans will find them.
Step 3: Prepare the Ground
Prepare the ground where you are planning on planting your beans by removing all grass/weeds. Mix up the dirt and add some fresh compost if you have any available. Make shallow trenches about one inch deep and about six inches apart running parallel to the length of your trellis.
Step 4: Plant the Seeds
Drop the bean seeds in these trenches, no closer than 3 inches apart. Cover with dirt, then water and wait.
Step 5: Fertilize
This step is completely optional. Beans are very easy to grow, even in soil that isn't the best. In my last planting of beans, I did some experiments with fertilizing some of my beans with rabbit manure while letting the rest of the beans grow completely naturally. The plants with the manure produced about quadruple the about of beans and fruited about a month before the beans that only had water.
So needless to say, fertilizing with manure definitely helps. I've never tried a store bought fertilizer with beans, but I'm sure Google can help. If you have a small pet rodent such as a rabbit though, you get a almost unlimited free supply of little round pellets of bean fertilizer.
Step 6: Wait...
Continue to water your beans every day. In about a week, the seeds will start to germinate and pop out of the ground. In a few more weeks their tendrils will start reaching for the sky and once they touch something they can climb up, they will reach the top in no time at all. Next they will start flowering, and fruit will follow.
Step 7: Harvest
Soon your beans will be ready to harvest. They will turn their proper color and reach lengths of up to two feet long. If the beans are picked when they are smaller, they will be more tender, but you won't get the impressive size. If you try to get the beans as big as possible, keep a close eye on them and make sure you pick them just before they go to seed.
Step 8: Eat
Eating the beans is the best part of the whole process. You can eat them raw, right off of the plant, but you can also cook the beans. My favorite method of cooking is to cut and clean the beans, then stir fry them with garlic, onions, home grown malabar spinach, sesame seeds, and a little butter and soy sauce or hoisin. When cooked this way, the beans can be eaten alone, or can be topped over rice or pasta for a complete meal.