A comment was just posted yesterday which posed the simple question, “The tree will grow on from that few roots?” The question was prompted by this photo:
Well, there’s not much left of this riverflat hawthorn, right? Just what the bonsai artist needs, of course, which is the key part of the process of turning a natural tree specimen into a bonsai. But what about those severely cut back roots? What’s going to feed the tree till spring?
One of the common myths about deciduous trees is that they store food in their roots in order to survive winter. Exclusive winter root food storage is limited to root crops such as potatoes, carrots, onions, etc. and ornamentals such as lillies and irises. To be sure, some food storage occurs in the root zone of deciduous trees, but the fact is food is stored throughout the tree in the form of starch. This starch is held in solution in the tree’s sap. Because the plant’s metabolic rate slows dramatically during dormancy, just as a hibernating bear’s does, the stored starch is utilized at a very, very slow rate. Sap does not flow during winter, so the individual cells of the tree stay alive by the very slow utilization of starch reserves. This makes perfect sense, when you think about it. There is no active cell growth, since the tree has no need of it. There are no leaves taking in sunshine and CO2 to produce food for the plant’s overall growth and to fuel other metabolic functions. There is no transport of hormones and food to the roots of the plant to make them extend further to support growth of the above ground part of the tree. All that’s really needed is the maintenance of cell structure, meaning internal cell pressure which is a direct result of the presence of sap.
So returning to the question about the dramatic root reduction on this hawthorn, I know the tree can regrow roots and shoots because the tree essentially “wants” to live. It doesn’t regrow roots and shoots because a certain volume of roots has been retained in the collection process. And because I know this, I can plan the future life of this tree as a bonsai by chopping enough of the roots to allow for proper tapering of each of the large roots that were growing in the wild, not to mention ensuring the tree will fit properly in its future bonsai pot.
Sure enough, this tree actually put out new foliage during our unseasonably warm November. Growth has stopped now, but I have complete confidence this specimen will come through winter just fine.
One final note on root reduction when collecting deciduous trees: when you observe a tree growing in the wild that you intend to collect, notice the spread of the above ground part of the tree. Then use your imagination to picture a root system of equal volume below ground. Notice I didn’t say equal spread, because the root system of a tree spreads far beyond the edges of the part you see above ground. Its configuration is basically flattened out, because there’s relatively little oxygen beyond the first foot or two of soil. (If you’ve ever seen a mature tree uprooted during a storm, you’ve observed more or less a “pancake” of root and soil the tree was “sitting” on. Why is this root and soil mass confined to within the spread of the tree’s crown? Simply because the smaller, finer feeder roots snap off when the tree falls over, remaining in the ground. What you see is the larger, hardened off roots closer to the tree held intact.) The point of this is, when we collect deciduous trees and drastically reduce the root zone, we also drastically reduce the above ground structure of the tree. In essence this maintains a balance. When the tree comes out in spring, the growth of shoots will be more or less reflected by the growth of roots.
So whenever we go out in winter to “capture” hibernating trees, we can do so with confidence. We can also make the necessary root zone reductions in order to be able to place our future bonsai in their pots without having to re-chop the large roots. New roots sprout readily from the cut ends.