How Much Water Does a Giant Redwood Tree Need?

Giant redwood trees come in two types. Coast redwoods live in damp forests along the coast of northern California where snow is not common and yearly rainfall is high. These trees are the tallest trees in the world. Giant sequoia live in the Sierra Nevada mountain habitats where summers are warmer and drier and winter snowpack limits water availability. Both redwoods need a lot of water.

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Fog provides a large amount of the water needed by coast redwoods.

Water Loss

Redwood trees, like all plants, open gas exchange pores called stomata on their leaves to take in carbon dioxide for photosynthesis to produce sugars for growth. Water vapor lost during this process is called transpiration. The cloudy wet habitat of the coast redwoods allows them to grow faster. Giant sequoia have fewer stomata on their leaves to reduce water loss during dry weather and this contributes to slower growth.

Very Large Trees

Coast redwood forests are so dense that the amount of plant matter (biomass) is several times more than in a tropical rainforest. One old coast redwood has enough wood to make 20 three-bedroom houses and a giant sequoia has at least twice that amount. The General Sherman Tree has 600,000 board feet and the trunk itself weighs nearly 3,000,000 pounds, according to a webpage on the Palomar College website. About half the weight is water.

Coast Redwood Water Needs

Coast redwood habitat receives less summer rain than in the winter but nearly every day is foggy. According to a 1998 report in the journal Oecologia, redwoods use more than 600 quarts of water each day in the summer and up to 40 percent of it is from the fog. These trees produce canopy roots on high branches that absorb fog water. Other plants grow on these trees and collect soil in branch depressions that hold moisture the tree uses.

Giant Sequoia Water Needs

Giant sequoia grow in mountain habitats near streams so, even though the summers are drier than those where the coast redwoods grow, enough water is still available to the trees, except during severe droughts. During the winter months, deep snow ties up some of the moisture. These trees grow much slower, have a lower transpiration rate and use less water than the coast redwoods.