Re: Why do the largest redwoods twist about their vertical axis?

Many trees display a twisted wood grain, especially conifers of some age. Presently there isn’t a truly satisfactory explanation that I am aware of. Specifically you ask, "Does this twist help them carry their huge compressive load?" The answer would seem to be, "No."

A spiral wood grain makes the trunk more flexible, but not stronger. Flexibility may confer more safety than greater rigidity. Trees that can sway, particularly tall trees, are less likely to have their trunks snap or buckle from a lateral force. If the angle of the spiral becomes too great it certainly decreases the strength of the trunk. At a very basic level, all plants display spiral growth, and the tips of young plants grow in a spiral pattern called circumnuation.

If you look around, you can find some nice time lapse videos of this growth. Such a growth pattern may not be obvious in big woody plants, but may well be reflected in the pattern of cambial growth. The vascular cambium is the lateral meristem responsible for the annual production of wood to the inside and phloem to the outside, and is manifest as growth rings in the wood.