Tree of the Week: Hybrid chitalpa, available in two varieties

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The chitalpa -- x Chitalpa tashkentensis

In the early ‘60s, Professor F.N. Rusanov of the Uzbek Academy of Sciences Botanical Garden in Tashkent, Uzbekistan, decided to cross two related but quite different plant genera in the Bignonia family: the narrow leaf desert willow, Chilopsis linearis, native to the U.S. Southwest, and the broad-leaf common catalpa, Catalpa bignoniodes, from the U.S. Southeast, so that he would end up with the best characteristics of both parents. The hybrid plant combines the larger flowers of the common catalpa with the toughness of both parents, but is sterile, so drops no fruit or seed. In 1977 an expedition from New York’s Cary Arboretum brought cuttings from the nameless expatriate back to this country. In 1991 Claremont’s Rancho Santa Ana Botanic Garden named the tree chitalpa.

New trees that add to the value of a house or street are always welcome. Nowadays they might even be engineered for extra carbon storage so that they could have effect on global warming too. But whether the chitalpa is a valuable addition to our repertoire hasn’t been answered yet. Some people think it’s beautiful, others call it weedy.

The chitalpa grows fast into a 20- to 30-foot-tall and wide, bushy, but open deciduous tree. But it never knows where to send up its branches, so it needs disciplined early pruning to shape it into a pleasing tree form and some follow-up to keep it there and prevent suckering. The bark is gray and smooth. The leaves are 4 to 5 inches long, 1 inch wide, dull green and hairy. Trumpet-shaped, 2-inch-long flowers appear in erect clusters, bloom for a long time and are attractive to hummingbirds and bees. Since the tree is mainly sterile, the big beans of its catalpa parent do not develop. The tree is drought-resistant, cold-hardy to minus 15 degrees F, and not particular as to soil. Roots go down deep. The tree may be bothered by mildew in moister climates and aphids in drier ones.

The variety Pink Dawn has pink flowers and is the most commonly sold selection. Morning Cloud has pale pink to white flowers, grows a little more upright and larger, and is a little more resistant to powdery mildew.

--Pieter Severynen

Thoughts? Comments?