City Trees

Becky Schwartz Q&A with Brandon Au What is a tree in your region that you think is underutilized for urban use? 'Wilhelmina Tenney' rainbow shower tree (Cassia × nealiae) Is this tree readily available for purchase? Not yet, as growers are still becoming familiar with this cultivar. In what urban conditions have you seen this species thrive? I've seen it mostly as a street tree— and in some parks or open areas—on Oahu. In what conditions have you seen it not thrive? Coastal areas What are the beautiful features of this tree? 'Wilhelmina Tenney' has deep watermel- on-red blooms from April to September, with heaviest flowering in July and August. What soil conditions can it tolerate? Most soil conditions except sandy textured soils. What watering regiment is required? Once estab- lished, supplemental watering is not typically needed except during prolonged dry summer spells. What are tree care considerations? Frequent pruning is needed to contain the canopy and the fast growing water sprouts. Structural pruning should be performed when the tree is young. Transplanting considerations? Containerized or field stock are okay depending on the structure and health of the tree. What is the story of this hybrid? According to Staples and Herbst in A Tropical Garden Flora: Plants Cultivated in The Hawaiian Islands and Other Tropical Places, the original plant that came to be known as the cul- tivar 'Wilhelmina Tenney' was a seedling of a rainbow shower tree (Cassia × nealiae) found growing in the front yard of Captain J. C. Lorenzen's home on Lunalilo Street in Honolulu. This chance seedling was given to the next-door neighbors, the Tenneys, around 1920. The original tree was cut down in 1947, but fortu- nately it had been propagated several times during its lifetime, and one of the offspring was planted in the yard of the Makiki Heights Drive home of the Tenney's daughter, Wilhelmina (1891-1951). Although the latter tree apparently no longer survives, Wilhelmina donated a tree propagated from the one in her yard to Foster Botanical Garden in Honolulu, where it resides today. 'Wilhelmina Tenney' was designated as the official tree of Honolulu in 1965 by then-Honolulu Mayor Neal Blaisdell. What else would you like to say about 'Wilhelmina Tenney'? This is a tough tree that can withstand the urban environment but as with any tree, the tree has to be matched appropriately to site conditions. This tree compartmentalizes wounds well and as such can deal uncommonly well with vehicles hitting the trunk and branches. It can reach 30 to 50 feet (9 to 15 m) tall and 20 to 40 feet (6 to 12 m) wide and is hardy in Zones 10 to 12. When it's in bloom, 'Wilhelmina Tenney' stands out above the rest. The flowers o 'Wilhelmina Tenney', shown here in late May, will deepen to a watermelon-red in summer. Trunk of a mature 'Wilhelmina Tenney'. urban-forestry.com 39

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