One of the most beautiful ornamental trees is the Eastern Redbud, Cercis canadensis. It is a native of the eastern and southern U.S. and has “naturalized” in older Boulder neighborhoods. It’s most distinctive feature is its reddish purple buds followed by intense purplish-pink pea-like flowers in late April before the leaves come out. This wondrous and heart-warming display is greatly appreciated so early in spring but cannot be counted on if winters are too harsh.
It is a smaller tree 20’-25’ high and wide with attractive bark and heart-shaped leaves which are shiny and purplish when young. Fall color is yellow. It is said to be hardy to zone 4 and we have many fine specimens in Boulder.
However there are also many examples of young Redbuds dying to the ground and beautiful canopies split and mangled in snow and wind storms. So is it a good tree for our area or not? After working for fifteen years as an arborist here in Boulder, I wasn’t clear so I talked with some knowledgeable people. Rob at Left Hand Valley said there are other trees that are better adapted but if you want to plant a Redbud protect it from western sun and wind. Keith at Little Valley agreed that it is an understory tree and does better planted on north and east sites. He also knows a landscaper who expects it to die to the ground the first year, knowing it will come back strong from the roots. Gary Epstein from Ft. Collins Nursery said after twenty years of trying to grow good Redbuds, he doesn’t think that a northern seed source solves the winter-kill problem. He believes that the root system needs to get below the frost line before the top is hardy. His experience is that even if it dies to the ground several years, it can eventually make a good and hardy tree.
So here are my recommendations for success with Redbud: Plant a small tree one and a half inches in diameter or less in well-drained soil (clay is OK if it’s not soggy). Site it for some sun and wind protection (although good specimens exist in full sun and harsh sites); some shade is fine, but not full shade. Since it has a tendency for narrow, weak branching, make sure when you buy it that the major crotches are wide without clefts down the middle, otherwise the tree could split to the ground in a heavy snow; and prune out weak branches. Mulch heavily the first two or three winters, possibly using fencing tied into a four foot cylinder around the tree and filled with leaves.If it should die to the ground, cut the dead trunk to the ground and thin out the new shoots to three or to just one. Once established, water thoroughly once month and feed with aged manure in the fall. As it gets big,thin out the branches to let in light and keep from breaking under snow lead.
For a Siberian elm or a poplar, this would be too much trouble, but for a lovely Redbud, I think I’ll try it myself this year.