One of my favorite childhood memories is of the annual wait of my sister and I for the frilly flowers of Catalpa speciosa, Hardy Catalpa, to mature into long, thin, gigantic 'beans' that dangled from the tree like so many huge stringbeans from Jack's legendary beanstalk. These spectacular fruit made wonderful toys for all sorts of games - from pretend gardening, to the rather less idyllic 'bean wars' around my grandfather's seemingly vast gardens. As I myself grew, I began to appreciate the flowers and tough nature of this plant equally as much as its universally appealing fruit. I was dismayed to learn, upon finally entering the halls of horticultural academe, that Catalpa is often placed in that rather arbitrary and awful category of 'weed tree'. 'Weed tree' is an appellation rarely deserved by any plant unfortunate enough to be placed in this group by hasty gardeners, but it is especially inappropriate for Catalpa.
There are two commonly seen species of Catalpa in residential gardens and landscapes. Both are US natives with overlapping ranges. C. speciosa, Hardy Catalpa, is often seen in the northeastern and southern mid-west parts of the US. It is the larger of the two, reaching 50 to 70 feet in height with an open, coarse spread of up to 40 feet. C. bignonioides, Southern Catalpa, is smaller in height with a more rounded canopy but equally coarse texture, and as the name suggests is more common in the southeastern states, including Florida and Louisiana.
Both species are exceptionally agreeable trees producing large, heart shaped, grass-green leaves with a decidedly tropical appearance and which are topped in late spring with upright, pyramidal clusters of frilly white flowers. The leaves do not develop any significant fall color. The flowers are speckled on the throat with yellow and purple and are somewhat similar in appearance to those of Aesculus spp. (the Horsechestnuts). There are slight differences in coloration and bloom time between the flowers of C. bignonioides and C. speciosa with more purple speckling, and later flowering on Southern Catalpa. The clusters of blooms of both species are 6-12 inches tall and quite striking, even from a distance, as they rise up from the foliage like floral candleabra throughout the canopy. In late summer and early fall, the flowers mature into the famous 'beans' or 'cigars' (Catalpa is sometimes called the 'Cigar tree') which eventually fall from the branches. Inside each fruit are a number of rather interesting dry, winged seed with fringed wings.
In addition to all of these wonderful attributes, Catalpa is an exceptionally tough landscape plant. It is well adapted to almost every modern landscape setting in full sun or part shade and will tolerate a broad range of soils and moisture conditions from dry sand to heavy clay. Both C. speciosa and C. bignonioides are completely cold hardy from the coast to the mountains of the southeastern US but Catalpa is generally somewhat weak-wooded and may lose branches during strong storms. Judicious pruning not only helps with this problem but can minimize any ungainly habit that develops over time. Some of the foliage will succumb to powdery mildew in wet years but the tree itself will continue to prosper. Catalpa is often one of the few remaining trees surviving on once residential lots that have been surrounded by urban sprawl and construction - it will flower and fruit reliably in the face of an army of bulldozers.
There are some interesting named hybrids and selections of Catalpa. Two cultivars of Southern Catalpa are 'Aurea', with canary yellow leaves which rapidly fade to green in the heat, and 'Nana' which is a rounded dwarf form that rarely flowers or fruits and is usually top-grafted onto a standard to make a 'pom-pom' style tree. C. bungei is a small, shrubby tree native to China and similar in apppearance to C. bignonioides 'Nana' but with some lobing on the leaves. C. fargesii, Farges Catalpa, is also native to China and bears distinctive, pink speckled flowers. C. ovata, Chinese Catalpa, is a third species from China with exceptionally long and thin fruit and yellow-cream flowers. C. x erubescens is the classification for a number of hybrids between C. ovata and C. bignonioides including the rich, burgundy leaved form 'Purpurescens' whose leaves and petioles emerge deep purple-wine in the spring, but fade to green when the summer heat sets in. Sadly, no doubt due to the undeserved 'weed tree' reputation, it is almost impossible to find any selections of Catalpa in main-stream commercial nurseries. Gardeners will need to hunt through specialty mail-order catalogs or propagate their own plants (which is not difficult) to add these unique garden beauties to their landscapes. Catalpa can be propagated readily from fresh seed, successfully grafted, or rooted easily from softwood stem cuttings, or from root cuttings taken in early winter.
Like other so-called 'weed trees' (e.g. Box Elder -Acer negundo, Tree of Heaven - Ailanthus altissima, Royal Paulownia - Paulownia tomentosa) Catalpa has many beautiful and appealing traits. Its very tough adaptability and apparant availability have branded it as a 'weed' - characteristics which are actually very valuable in facing the demands of today's urban desert landscapes. At The NCSU Arboretum (now the JC Raulston Arboretum), a number of different Catalpa have proven their mettle, and their beauty, in the Piedmont clay. Explore the gardens of the arboretum to discover the Catalpa, and see just how beautiful what is already in our own backyards can be.