I collected seeds from some of the oldest ones in Columbus back in the early 80s. I also picked seeds from old trees in the village of Chenequa in Waukesha County. For quite a few years we grew our seedlings up to landscape-sized trees. We had mixed results with this endeavor, losing many plants along each step of production. The younger and more vigorous the plants were, the more problems we had with them. It seemed the better the job I did of growing them the more I would lose over the winter. If the seedlings grew to 12” in height in my seedbeds, they would die back to 8”. If they grew to 18”, they would die back to 6”. The same thing would happen to the transplants that we put in the field. The most vigorous plants would die back. It didn’t matter which seed source it was. They died back. I began calling them Deadbuds.
So what was the problem?
It all relates to hardiness. This species is native south of Wisconsin, in Illinois, southern Iowa, and far southern Michigan as well as points east and further south. The plant has hardiness issues in Wisconsin that are primarily evident when plants are in the juvenile stage of life. The Columbus strain of Redbud is subject to this same problem, though not as severely as other strains. Young, vigorously growing Redbud plants continue to grow late into the season when most other species of plants that are well adapted to our area have stopped. These well-adapted plants are preparing for dormancy. The foolish unprepared Redbud youngsters are growing like gangbusters when they shouldn’t be. If they are not outright killed, they will have severe die-back which will promote even more vigorous growth the next season. This leads to more late growth that year and more susceptibility to the cruelties of winter. This cycle of die-back and vigorous growth can continue for many years in a row. I call these kinds of plants yo-yo plants. They grow up during the growing season, and then down over the winter. Then they go up the next season, and then down, like a yo-yo. This can happen for many years in a row. Sometimes the cycle can be interrupted by a series of mild winters when they can survive and not die back. Then the plant may be able to get to adulthood, at which point the tree slows down in growth and hardens up earlier for the winter each fall.