I have two very large (taller than a two story house, guessing over 2 foot diameter) dawn redwoods, both growing near my gravel drive. In fact, one is in the center of my gravel drive's turn-around with about a diameter equal to the span of the tree set off with large boulders to keep the gravel out. Anyway, I am considering either blacktopping or pouring concrete for my drive instead of gravel. Years ago I went to visit the Muir Woods reserve north of San Francisco and I remember something about the roots not wanting too much traffic, etc. These roots are already under the gravel and withstand traffic as it is with the gravel. Also, I do not want to hurt the trees if the blacktop or concrete would impede water to the roots. I would not blacktop or concrete right up to the trees; only where there is already gravel. The gravel is pretty thick, anyway, though. The trees were planted in the early 1950's as part of the project to see where they would survive across the country. I live in the Indianapolis, IN area. Your input would be greatly appreciated.
You can't count on this not killing the trees. You might be able to get away with it, and might not. You have to decide which you want more - the trees or the paving. Leaving an unpaved area close to the trunks has no effect on the condition of most of the roots which will form a large network extending well beyond the spread of the branches.
There is a difference between trees being planted and growing roots near existing gravel and hardtop, and placing hardtop over existing roots. Can you blacktop farther and leave a decorative gravel in the center? Not sure about Indianapolis, but I've seen Dawn Redwoods cause havoc to concrete driveways out here in the Portland, Oregon, area.
The trees already have a decorative circle of grassy area around them of about 12 foot in diameter. The roots extended beyond that area many years ago, and have been growing under the gravel for probably over 50 years. The gravel drive is probably 8 to 10 inches thick before hitting any dirt. I am not sure how permeable the gravel is given its thickness for water to percolate to the roots, anyway. But I really love the trees and do not want to hurt them. My intuition tells me that with the thickness of the gravel and the length of time the trees have been growing in the drive area, it probably would not make much difference if I topped the gravel, but there is still that seed of doubt in my mind. Have you seen other dawn redwoods where the roots can grow under a drive? I am guessing the water would percolate under the drive from the lawn area anyway because of the slope of the land. Thanks for your input.
