x Chitalpa tashkentensis

As a colleague of mine said: "Why in the world would anyone want to mess up a desert willow by crossing it with a catalpa?" Well, someone did, and the results are actually quite nice.

x Chitalpa tashkentensis is the grex name for a cross between Catalpa bignonioides and Chilopsis linearis. Chitalpa is hardy to USDA Hardiness Zone 6. It is well adapted to hot, dry locations as long as the soil drains well.

Chitalpa is a small to medium tree with open, upright branches and good form. Flowers are orchidlike and produced in July or August at the ends of new growth. Flowering begins in May in Southern California and continues well into late fall. Its leaves are longer and broader than desert willow, but much smaller than catalpa.

The initial hybrids between Catalpa and Chilopsis were created in Uzbekistan in 1964 and introduced to the United States by Robert Hebb of the New York Botanic Garden in 1977. (Chitalpa is a combination of the scientific name of the two parents, while the specific name identifies the city in Uzbekistan where the hybrids were created.) Although in cultivation in the United States during the 1980s, the hybrid remained unnamed until 1991 when Rancho Santa Ana Botanic Garden assigned the name x Chitalpa tashkentensis.

Two cultivars were subsequently named by Rancho Santa Ana: pink-flowering 'Pink Dawn' and white 'Morning Cloud.' 'Pink Dawn' is the showier of the two.

Growing tips

San Marcos Growers in Santa Barbara, Calif., provided some details on producing 'Pink Dawn':

Among the best features of 'Pink Dawn' are the abundant clusters of showy, pale-pink flowers with each cluster containing 15-40 flowers. The 1-inch-long flowers have a funnel-shaped throat with conspicuous purple nectar guides that line the inside and emerge to give orchid striping to the flared pink petal lobes.

Chitalpa is a fast-growing deciduous tree, branching readily near its base and with ascending branches that form a dense, broad oval crown. Although it is difficult to determine eventual size for these trees it has been speculated, based on the growth of the oldest specimens, that they will reach 20-25 feet tall.

It is a drought-resistant plant, a trait inherited from the desert willow, and it is fairly hardy, having withstood temperatures as low as 9F. It has been noted that it will freeze back to the ground in Zone 6.

Although many fast-growing trees are intolerant of windy situations, chitalpa can withstand even strong winds without breakage. Unlike either of its parents, chitalpa is sterile and produces no messy seed pods. Flowers dry on the plant rather then fall fresh and so they don't become a slick safety hazard on a sidewalk or patio.

It has been noted that chitalpa will mildew in southeastern U.S. sites and will do likewise in cool coastal areas. This tree also has a habit of suckering near the base, making it difficult to create a high-headed tree that might be necessary along walkways and in small patios.

The market is probably not huge for this grex, but it should be used more in landscapes that have room for a shrubby, open-flowering tree.

{sidebar id=28}

Specifics

Name: x Chitalpa tashkentensis

Common name: Chitalpa.

Description: Open, shrubby tree with orchidlike flowers in summer. For arid sites.

Dimensions: 25-30 feet tall; 10-15 feet wide.

Hardiness: USDA Hardiness Zones 6-9.

For more: San Marcos Growers, P.O. Box 6827, Santa Barbara, CA 93160; (805) 683-1561; fax (805) 964-1329; www.smgrowers.com

- Kevin Neal