Stem Caliper Growth In Tree Tubes
A customer emailed today with an excellent question: Are you noticing that with getting the trees to grow faster because of the tubes they are more spindly and do not stand up to the wind as much, or does this problem seem to correct itself over time?
I thought I’d share my reply, because I figure many other tree tube users and potential users probably have the same question/concern.
Great question on the growth issue. The answer is sort of a “Yes, but…” answer.
Yes, at the point in time a tree emerges from a tree tube it has a much thinner stem than an open grown tree of the same height would have (of course that’s assuming that the deer allow an open grown tree to reach that height 😉 That is because a) growth is channeled upward, and b) movement and shaking, which trigger stem caliper growth, are minimized.
If you were to remove the tube at that point you would have a pretty spindly tree. But, you don’t want to remove them at that point. Keep in mind that the tree tubes really have 4 functions: browse protection, growth enhancement, support, bark protection. So when the tree emerges the job of the tube is only half done. It’s important to keep the tubes on for support and bark protection for a few more years. Once the crown of the tree is exposed to full sun and wind you’ll notice that height growth will slow down and the trees will quickly add more caliper until they come back into balance. And of course nothing is more frustrating that getting a tree off to a good start only to have the bucks scrape it to shreds in the fall, so keeping the tubes on for a few more years also provides needed bark protection.
The second but is that Yes, the stems of trees grown in tree tubes are thinner, but that is much less true now than in the past. Larger diameter tubes, more light transmission into the tubes, vented tubes, and stakes that allow for some swaying and flexing all contribute to better stem caliper growth while the tree is growing in the tube. Today’s tree tube system much more closely approximates an open grown tree than the unvented, small diameter tubes of 10 or 15 years ago.
Other factors influence the growth of seedlings in tree tubes. Allowing grass and/or brush to grow tall next to the tubes shade the seedlings inside and encourages long, spindly growth reaching for the light. Aggressively controlling competition next to the tubes so the seedlings get full light from all angles further encourages better caliper growth.
Hope this answer helps, and as always if you have any other questions, please don’t hesitate to contact us!