California is so full of Eucalyptus trees that they seem to be a natural part of the landscape.
But Eucalyptus is not part of the native California landscape at all. Eucalyptus trees are native to Australia and some neighboring areas but not to Europe or the Americas. Eucalyptus trees have been introduced to California by humans, and they are considered to be invasive species replacing native trees, mainly oak.
Eucalyptus certainly grows faster than redwood. Some species of Eucalyptus trees even grow impressively huge (the largest specimens of some species can be taller than a redwood tree). On the downside young Eucalyptus trees are pretty useless for timber as the wood tends to warp as it dries.
Eucalyptus provides almost no shade as the leaves tend to grow with the edge positioned vertically as an adaptation to very strong light and heat from the sun.
Eucalyptus wood, bark, the oil in the live plant are all highly flammable. In fact the oils evaporating from the foliage act as an accelerant and spread wild fires pretty quickly.
Which is not good in an area already prone to forest fires, such as California.
Unlike redwood which is nearly fireproof, Eucalyptus tends to burn quickly, and even facilitate the spread of a forest fire. The trunk of an Eucalyptus tree stays alive in a fire and it is capable sprouting fresh growth. Thus the Eucalyptus tree survives serious fire damage, where other plants don’t.
The regeneration after a severe burn, along with its ability to spread the fire quickly may be an adaptation to get rid of the competition, which is not necessarily good for biodiversity, and can be outright devastating to the native flora that has not evolved to survive in an Eucalyptus forest.
A large growth of Eucalyptus trees in a dry and hot climate represent a serious fire hazard.
Eucalyptus: California Icon, Fire Hazard and Invasive Species
Eucalyptus on Wikipedia.