01/03/2026
Ever wondered why giant redwoods grow so tall? Well first of all let's be clear what we mean by a giant redwood.
The giant trees of California are primarily the Giant Sequoia (Sequoiadendron giganteum), known for massive volume in the Sierra Nevada, and the Coast Redwood (Sequoia sempervirens), the world's tallest trees found along the coast. Notable individual giant sequoias include the General Grant, The President, and the Grizzly Giant.
Next, what is the primary limiter on the height to which most trees can grow. The answer? It's called the hydraulic limitation hypothesis.
Simply put, under normal conditions water moves up through the tree's vascular tissue (xylem) using cohesion-tension. As the trees get taller, the distance for water to travel increases, as does the force of gravity working against it. Now, If the tension required to pull water to the top exceeds a critical threshold, the water column in the xylem can break, causing air bubbles (embolisms) to form, which stop the flow entirely.
So ultimately they are defeated by gravity. But why do these two particular species manage to grow so much taller than other trees?
To understand that you need to look at their local environment as well as some quite clever adaptations the tree themselves have developed.
First, where they grow in Northern California is known as the "fog belt". In this unique environment redwoods are able to absorb up to 40% of their moisture directly through their needles from the air. This bypasses the need to pull every drop of water from the roots, which is where most other trees hit a physical limit.
Second they happen to be really good at not dying!
They have specialised Leaf Structures: Leaves at the very top of the tree are shaped differently and can store up to five times more water than those at the bottom, helping them survive dry periods even when they are too high for groundwater to reach them.
Fire & Pest Resistance: Their bark contains high levels of tannin, which makes the wood unappealing to insects and highly resistant to decay and fire.
Interconnected Support: Despite being the tallest things on Earth, their roots are surprisingly shallow (only 6–12 feet deep). They stay upright by intertwining their roots with neighbouring redwoods, creating a massive, stable "friendship circle" that protects the whole grove from being blown over by high winds.
