Bamboo stalks turn yellow when the plant is very unhealthy and dying, this change is caused by a number of factors. Dehydration is the most common reason for a bamboo stalk to yellow. Going without any water for a short amount of time hardens the pores that the plant uses to bring water into the plant. This hardening is permanent, making the plant unable to hydrate itself even if water is added later.
A bamboo plant that starts to yellow needs immediate attention. When the bamboo stalk starts to yellow before the leaves, the problem likely started at the base. Too much fertilizer, the wrong type of fertilizer, dirty water and lack of water are likely causes of yellowing bamboo.
If a stalk of bamboo turns yellow, it needs to be removed from plant arrangements to prevent it from affecting the other plants. If the leaves yellow first, there is more time to correct any issues in the plant's environment. Bamboo plants need indirect sunlight, a comfortable, room-temperature environment and plenty of water. Fertilizers that are meant for soil-grown plants are not recommended for bamboo plants because of the intense strength of the fertilizers. Bamboo plants are also sensitive to frequent pruning.