At temperature higher than 50 F, long bean seeds can sprout. In a week, long bean will grow cotyledon. In order to maximize its growing season, indoor seed starting is highly recommended. Sow long bean seeds in seed starter directly, keep the soil light to medium wet and do not over water for long bean cannot withstand water-logging.
Planting Long Beans
Depending on temperature, it may take 2~3 weeks to grow about 1 ft long and you will see the plants are growing vines. They will need to get transplanted as soon as possible, or the vines will tangle together and turn it over to bury the fertilizer underneath.
Spread some inorganic fertilizer and mix with top soil, place the seedlings at least 1 foot apart in a row. Plant distance depends on your trellis height, row distance and sunlight hours. Dig a hole and bury the plug in the soil. Fully water your seedlings after transplanting. If you use drip system, turn it on.
Outdoor Planting
If outdoor temperature is higher than 60 F, long bean will get straight into fast growing stage. In the first week, the vines will grow longer and try to grab something to climb, so you should build a trellis, and direct the vines up to the fence.
Tie a string onto top bar, pull it to the middle bar and make a single knot, extend the string to the bean vine, make a loose single knot on to the stem and twin the vine and string together. Usually one or two vines on one string is good. Remove any flower buds or side sprouts under 1 ft, this will let the nutrients focus main vine and produce more and high quality beans.
Flowering
Long bean vines grow extremely fast. Some flowers start to grow bigger from the main vine, almost a flower at every leaf, at the same time, together with the flower, one or two side vines are growing.
With some good pruning, you can make your long bean produce more beans than vines. Keep 2~4 leaves on side vines and remove the tips. When main vines reached the top of fence, also remove the tip. Whenever you see a new vine, readily remove the tip. Try to do it as much as you can, but it doesn’t have to be perfect. Very soon, you will see that the side vines are developing flower buds too. At the same time, long beans start to hang from the bottom of the trellis.
Fertilizer Application
Spread some mixed 10:10:10 fertilizer next to long beans roots, mix it gently with top soil and now you have the bottom beans to pick. The fertilizer will help the beans in the middle grow bigger. The same thing when the middle beans are ready to pick, spread more fertilizer to help the top beans to grow from bottom to top. The lower beans are full size and can be picked, middle beans are tinny and the flowers are blooming on the top. If the long beans are not pruned the vines grow very heavy, lot of side vines are long but not fruiting and at the top, the vines grow into a messy, dense and heavy “hat”, therefore the beans are obviously small and short.
By proper pruning and compensating fertilizer, long bean can continue to produce high quality beans up to 4 weeks then it will slow down. The beans get thinner and shorter, leaves starts fading and even distills producing. At this stage I suggest you remove the vines to keep the space for other vegetables to continue to supply your kitchen.
