In general, bamboo is a fairly versatile plant and can be relatively drought tolerant. Bamboo grows best with ample water but the roots must not become soggy and waterlogged. Having soil that is constantly over saturated with water will suffocate the roots from air and can cause the roots to rot. As long as the soil allows good drainage and is well aerated, overwatering bamboo is not a concern.
Newly planted bamboos in the ground require frequent watering. They should be watered twice a week during summer and more often if the weather is hot and windy. As the bamboo matures and the root system becomes more established, the bamboo can become more drought tolerant. However, even mature bamboo groves can be distressed from lack of water during shooting season. Water stress can cause the bamboo to abort new shoots.
Bamboo grown in pots and containers do not retain moisture as well as bamboos grown in the ground. During summertime, potted bamboo should be watered three to four times a week or roughly every other day.
Applying mulch to bamboo is a terrific way of helping the surrounding soil retain moisture. See Mulching Bamboo.
Most often if bamboo is underwatered, the leaves will roll inward and if severe enough, will begin to drop its leaves.
Unlike the majority of plants, a very unique characteristic of bamboo is that it renews it's leaves in the Spring season. During this period, the leaves will wither, drop and grow new foliage. Spring time is the Autumn season for bamboo! Often, this behavior can be mistaken for underwatering or plant issues.
Some shade loving species of bamboo will curl up their leaves when exposed to direct, hot sunlight. Typically, the foliage of these particular bamboos will uncurl once the hot sunlight disappears. This too can also be mistaken for lack of water.