× Chitalpa is an intergeneric hybrid between Catalpa and Chilopsis, both genuses belonging to the Bignonaceae family. Intergeneric hyrbids are rare, both in nature and in cultivation, as it is rare to find two different genuses that are genetically and physically compatible enough to produce offspring together. To my knowledge, the only existing cross in this taxon is × Chitalpa tashkensis which is a cross between Chilopsis linearis and Catalpa bignoides.
Chitalpas are intermediate between their parents, inheriting some of the bushy habit of Chilopsis, but some of the height and strange branch patterns of Catalpa. The flowers are usually a light pink, also midway between their parents. They are fast growing like Catalpa, but also drought resistant like Chilopsis. For these reasons, the tree was briefly among the more hot horticultural commodities, with many planted throughout the region in a fairly short period of time.
Unfortunately Chitalpa comes with a fatal flaw. The tree virtually always comes down with a case of Xylella fastidiosa (AKA bacterial leaf scorch), an incurable and usually fatal bacterial disease. The disease progresses slowly and can easily be missed, but comes back each year a little worse until the tree dies. This tree is largely propagated clonally, and because the early stages of infection are largely asymptomatic, it's thought that cuttings taken from infected mother trees carry the disease but don't become sick for years to come. If this is true, it may be possible to find rare trees that are not infected, and propagate those, or to grow new trees from cell culture that may not contain the disease. However, to my knowledge, this has not been done and growers are largely ignoring the issue and taking advantage of naïve customers. All too common in the nursery industry. Even if this issue was solved, the disease can also be transmitted by insects, although it is unclear to me how common this is in our area. I suspect not very due to the local success of both parent species. For the time being, it is not wise to plant this tree, despite its many positive characteristics.
Chitalpas are intermediate between their parents, inheriting some of the bushy habit of Chilopsis, but some of the height and strange branch patterns of Catalpa. The flowers are usually a light pink, also midway between their parents. They are fast growing like Catalpa, but also drought resistant like Chilopsis. For these reasons, the tree was briefly among the more hot horticultural commodities, with many planted throughout the region in a fairly short period of time.
Unfortunately Chitalpa comes with a fatal flaw. The tree virtually always comes down with a case of Xylella fastidiosa (AKA bacterial leaf scorch), an incurable and usually fatal bacterial disease. The disease progresses slowly and can easily be missed, but comes back each year a little worse until the tree dies. This tree is largely propagated clonally, and because the early stages of infection are largely asymptomatic, it's thought that cuttings taken from infected mother trees carry the disease but don't become sick for years to come. If this is true, it may be possible to find rare trees that are not infected, and propagate those, or to grow new trees from cell culture that may not contain the disease. However, to my knowledge, this has not been done and growers are largely ignoring the issue and taking advantage of naïve customers. All too common in the nursery industry. Even if this issue was solved, the disease can also be transmitted by insects, although it is unclear to me how common this is in our area. I suspect not very due to the local success of both parent species. For the time being, it is not wise to plant this tree, despite its many positive characteristics.