Muir Woods is host to some of the most ancient trees on the West Coast. A redwood tree begins as a seed the size of a pin head and may grow to a height of 360 feet and a circumference of 25 feet at the base. This is comparable to the height of some of San Francisco's tallest buildings. California's natural Northern Coastal climate provides the ideal combination of longitude and elevation but also limits the range of these massive trees to few hundred miles up and down the western coast. The proximity to the Pacific Ocean keeps the trees damp all year long which is one of the most favored climactic conditions by the coast redwood. These perfect weather conditions have existed for 20 million years, and this can be seen by the age of some of the trees in this particular range. It is natural to age a redwood at 600 years old and some may reach ages of 2,000 years or more.
Not only are these trees separated from other species because of their longevity, but they also have very few natural enemies. The redwood produces a large amount of tannin which protects from most insects and disease. Another natural feature of the redwood is the ability to live in a compact environment. While walking through Muir Woods a visitor will notice the denseness of the forest which is due to the trees long life and resistance to disease as well as a natural precipitation generator. The thick coastal fog is drawn in from the ocean when inland temperatures are high. The dense greenery of the trees collects the moisture and allows the water to drip to the forest floor. One of the most important factors for the survival of a redwood forest is its own habitat and the moisture collected from the fog is vital to all life within the forest. A healthy redwood habitat includes many plants that use the coastal fog for nutrients. In Muir Woods some of the trees that can be seen growing alongside the redwoods are tanoaks, madrones and sequoia. This biotic community is very small and Muir Woods is one of the few places where visitors can experience it first hand.