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Catalpa bignonioides

Scientific name	:	Catalpa bignonioides
Synonyms	:	Catalpa catalpa
Origin	:	Southeastern United States
Description	:	The two native catalpa of North America are in many ways quite similar, with the southern catalpa generally being smaller and less hardy than its northern close relative. Both have simple heart-shaped leaves that are green on the top surface and lighter green beneath, often with a downy texture. Both have extrafloral nectaries on the undersurface of the leaves at junctures of major veins. The leaves are attached oppositely or in whorls (three per node) around the stem. The flowers of both are quite showy, have five lobes, upper and lower lips, and appear after the leaves are nearly fully, or fully developed. Externally the fruits are vaguely reminiscent of oversized string beans, but internally are divided longitudinally into two “packets”, each with many double-winged seeds. The seed pods frequently remain on the tree for much of the winter and open along two seams in spring to release the seeds. Many of the identifying characteristics that separate the two species are presented in Table 1.
Distribution	:	In addition to the U. S. distribution, southern catalpa can be found growing in the warmer areas of Canada. Dirr[3] considers it a Zone 5 to 9 species that is frequently used as a landscape plant. In its native habitat it is most usually found growing on river floodplains and bottomlands. While it prefers such sites, it can be grown on drier sites as well.
Blooming period	:	In Michigan the species blooms in June and July[1], in Oregon it blooms in June[2], in Athens, GA, it blooms in mid to late May, and in Boston, mid to late June[3].
Importance	:	Given the fact that the specie sometimes apparently produces considerable extrafloral nectar (see later) as well as apparently secreting floral nectar abundantly, surprising little appears in the American beekeeping literature about C. bignonioides. Burgett et al. [2] state that the species is a heavy yielder of nectar, but that it is sufficiently uncommon in Oregon to not be an important honey plant there. Pammel and King[13] describe the floral nectar glands as being located at the base of the corolla and at the base of the stamens which arise from the corolla. The gland, which is colored a light orange-yellow, extends up for about 3 mm on the stamens and the corolla and secretes nectar abundantly. The nectar then collects around the base of the ovary. Larsson and Shuel[4] state that some members of the species are excellent nectar producers and rate the species as a 2 on a 1 to 3 scale, indicating good nectar production that sometimes gives a surplus. For attractiveness to bees they rate it as a 2 on a 1 to 4 scale, indicating moderate foraging by bees. From his extensive questionnaires, Oertel[12] found that the species was at least of some importance in OK, KS and PA. Additionally the genus, which likely included C. bignonioides was found to be of some importance in CA, IA, IL, IN, VA and WA. The species has been planted in many parts of the world, and in 1938 a Dr. J. Schiller[16] from Austria published the following quotes in the American Bee Journal concerning the production of extrafloral nectar. “Nectar formation in the weak scented flowers is abundant and they are worked both by honeybees and bumblebees. It is unique, however, in that for a week before the blossoms appear a peculiar fragrance is common from the leaves and there is an abundance of nectar from numerous nectaries on the undersides of the leaves during the entire period of blooming and for eight or ten days afterward...The vigor of the nectar secretion of the leaf nectaries is dependent upon the warmth and humidity of both the air and soil. Early in the morning, large drops occur on the leaves which have not yet been visited by bees. The nectar also issues abundantly through the day when two or three bees may be seen on each large nectary quietly sucking......As the catalpa trees are visited by the bees often eight days before blossoming, when the trees do blossom the foraging bees divide into two lots according to their activity, one working on the leaves and one on the blossoms. Upon seeing the Schiller report, Oertel[11] commented that he had seen similar bee behavior associated with the species, but the report was not as glowing as that of Schiller’s. My interpretation of his comments are that he observed the behavior a month after the blossoms had dropped and that the bees worked the extrafloral nectaries very little during the period he observed the activity. I have personally observed bees working the blossoms. The blossom is so wide bees can crawl right down into the source of the nectar. My observations would not, however, lead me to classify the species as being “super attractive” to bees. I have not observed bees working the extrafloral nectaries even though I have seen them damp at times, presumably with extrafloral nectar. From the standpoint of honey production, I have no way of judging the relative importance of the two nectaries.
Pollen	:	The literature suggests that bees collect pollen from the species, but there seems to be little information beyond that.
Additional information	:	The species is much planted for its showy floral displays and attractive large leaves. At least two cultivars are available. ‘Aurea’, sometimes called the golden leaved catalpa, maintains a yellowish leaf cast throughout the summer. The cultivar ‘Nana’ is said to rarely, if ever, flower[3]. The species escapes cultivation frequently and is considered to be invasive and weedy. While it is frequently planted as an ornamental, those who do so will find it drops heavy loads of flowers after bloom, and a goodly supply of large leaves in the fall, and sometime later, during winter or early spring, it drops its crop of the large seed pods. The tree is also attractive to the catalpa sphinx moth whose numerous large larvae, which look a bit like tomato hornworms dressed in yellow and black suits, would not be considered by many to be an attractive feature of the tree. At times they can nearly defoliate the tree. They are said, however, to be good fish bait, and the trees are sometimes grown for the purpose of raising the caterpillars. The species is at times planted for fence posts and windbreaks. It is shade intolerant.
Reference	:	1. Barnes, B. V., W. H. Wagner.1981. Michigan Trees. The University of Michigan Press. Ann Arbor. 2. Burgett, D. M., B. A. Stringer and L. D. Johnston. 1989. Nectar and Pollen Plants of Oregon and the Pacific Northwest. Honeystone Press. Blodgett, OR. 3. Dirr, M. A. 1998. Manual of Woody Landscape Plants. Stipes Publishing L.L.C. Champaign, IL. 4. Larsson, H. C. and R. Shuel. 1992. Nectar Trees, Shrubs and Herbs of Ontario. (C. D. Scott-Dupree, Ed.). Publication 82. Ontario Minister of Agriculture and Food. 5. Lovell, J. 1926. Honey Plants of North America. A. I. Root Co. Medina, OH. 6. Milum, V. G. 1957. Illinois Honey and Pollen Plants. Contributions from the Department of Horticulture, University of Illinois, Urbana IL. 7. Morton Arboretum Staff. 1990. Woody Plants of The Morton Arboretum. The Morton Arboretum. Lisle, IL. 8. Morton, J. A. 1964. Honeybee plants of South Florida. Proceedings, Florida State Horicultural Society 77:415-436. 9. Morton, J. F. 1981. 500 Plants of South Florida. Fairchild Tropical Garden. Miami, Florida. 10. Nye, W. P. 1971. Nectar and Pollen Plants of Utah. Utah State University Monograph Series, Volume XVIII, Number 3. Utah State University Press. Logan, UT. 11. Oertel, E. 1938. Untitled comments. American Bee Journal 78:403. 12. Oertel, E. 1939. Honey and Pollen Plants of the United States (U. S. D. A. Circular 554) U. S. Government Printing Office. Washington D. C. 13. Pammel, L. H. and C. M. King. 1930. Honey Plants of Iowa. Iowa Geological Survey Bulletin No. 7. Iowa Geological Survey, State of Iowa. Des Moines. 14. Pellett, F. C. 1978. American Honey Plants. Dadant and Sons, Hamilton, IL. 15. Sanborn, C. E. and E. E. Scholl. 1908. Texas Honey Plants. Bulletin No. 102, Texas Agricultural Experiment Stations. College Station. Texas. 16. Schiller, Dr. J. 1938. The Catalpa Tree as a two-Fold Nectar Source. American Bee Journal 78:329-320. 17. USDA, NRCS. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA 18. Vansell, G. H. 1949. Pollen and Nectar Plants of Utah. Circular 124, Agricultural Experiment Station, Utah Agricultural College. 19. Watkins, J. V. and T. J. Sheehan. 1975 Florida Landscape Plants--Native and exotic.(Revised edition). The University Presses of Florida. Gainesville, FL. 20. Wyman, D. 1950. Order of Bloom. Arnoldia 10(7-8):41-56.