|MadSci Network: Botany|
To my knowledge, the root is the most important organ for absorbing water, and once the root is destroyed, the plant can hardly recover. The redwood prefer not only the humidity of SF, but also the consisent mild temperature, I do not think the failure for water to reach high is the reason. Moreover, since there is complex vascular system connecting root and other part of plant, graft root is very difficult. A horticulture expert can give you more advice on it.
David Hershey adds the following:
It is possible for plants to absorb water through their leaves when it is foggy or the relative humidity is near 100% but it is not absolutely required for California redwood (Sequoia sempervirens). The main effect of fog seems to be reducing transpiration and condensing on the tree and adding water to the soil via "fog drip". California redwoods have been cultivated as landscape trees well outside their natural range in the coastal California fog belt, including warmer parts of Europe, especially England, the eastern United States, Australia, and New Zealand (Hewes 1981).
Although outside the California redwood natural range, the University of California at Davis, near Sacramento, has many California redwoods despite hot, dry summers. However, the trees in Davis must be irrigated. California redwood is considered an excellent landscape tree and can grow 3 to 5 feet per year (Sunset 1985). Cultivated trees have not yet reached the world record heights (over 300 feet) as in their natural habitat but have exceeded 200 feet in New Zealand (Redwood Home Page) and can reach 70 to 90 feet in 25 years (Sunset 1985).
Boston winters are too cold for California redwoods to survive because there are only hardy down to 5 to 10 degrees F (Wyman 1990). You might be able to grow Dawn redwood (Metasequoia glytostroboides) which is hardier.
Hewes, J.J. 1981. Redwoods: The World's Largest Trees. New York: Gallery Books. Redwood Home Page Sunset. 1985. New Western Garden Book. Menlo Park, CA: Lane. Wyman, D. 1990. Trees for American Gardens. New York: Macmillan.
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