1792 In April, the expedition led by British navigator Vancouver finally reached the west coast of North America after a long and arduous voyage. At that time, there were almost no outsiders except some indigenous Indian tribes, and when it comes to plants, the outside world knew nothing about them. When Zeiss, a naturalist in the expedition, set foot on this mysterious land, he was greatly shocked: on the rolling hills and quiet canyons, all kinds of grotesque and towering trees grew, especially a coniferous tree whose bark was deeply chopped into scales, its branches were pale yellow and its leaves were narrow and flat, which was the most spectacular. According to Menzies's estimation, this kind of tree is more than twice as tall as the tallest tree he has ever seen.

After Menzies returned to China with the expedition, what he saw and heard on the west coast of North America caused a great response from the British botany community. Thirty years later, a young Scotsman, David Douglas, was sent by the Royal Horticultural Society and finally embarked on a journey to uncover the mystery of this giant tree left by Menzies. After eight months at sea, Douglas landed on the west coast of North America in the early spring of 1825. His investigation is very difficult. He always wears a Scottish plaid coat and takes the lead in tasting the only "luxury"-tea. In most cases, he walked nearly 10 thousand kilometers alone, and most of the places he went were uninhabited areas. Because of Douglas's bravery, his investigation was very successful. He not only witnessed the "giant tree" mentioned by Menzies, but also collected complete plant specimens and a large number of seeds of this tree. Later, according to the specimens collected by Douglas, botanists identified this tree as a new species of Taxodium in Pinaceae, and called it "Taxodium Douglas" in memory of this brave Scotsman who devoted himself to science.

Douglas fir has been considered as one of the tallest tree species in the world since it was discovered. Some ancient trees over a thousand years old can grow to the height of 100 m, and the DBH of 10 m can be compared with Sequoia and Giant Sequoia, which are known as "giant sequoias in the world". According to Guinness World Records, a Douglas fir was measured in Lynn Valley on the west coast of Canada in 1902. The results show that it is one of the tallest trees that have been measured, with a height of 126.49 meters, which is more than ten meters higher than the tallest redwood.

Douglas fir, also known as yellow flag pine, is not only tall, but also has excellent wood, durability and beautiful texture. It is one of the most valuable and important timber trees in the world. Its crown is like a pagoda, its trunk is perfect and straight, and it is also suitable for the cultivation of landscape trees in gardens. Coincidentally, Douglas fir is indeed related to the flag. It is often used as a flagpole because of its good wood and tall trunk. 19 19, a flagpole with a height of 65 meters was erected in Kew Garden, the Royal Botanical Garden. This flagpole is a log made from the trunk of Douglas fir in British Columbia, Canada. The whole flagpole weighs 18 ton, and the top diameter is 30 cm. This may be the tallest single wooden flagpole in the world. When Douglas fir was cut down, people counted its annual rings, about 370, indicating that it still has great potential if it continues to grow.