Creeper family (Bignoniaceae)
This medium-sized tree is 40-70' tall at maturity, forming a trunk up to
3½' across and a crown that is more or less ovoid. The
stout trunk can be straight or somewhat crooked, while the larger
branches are ascending to widely spreading and rather crooked. On
mature trees, trunk bark is gray-brown, rough-textured, and
longitudinally furrowed between narrow scaly plates. The bark of larger
branches is more gray and less rough-textured, while young twigs are
brown to reddish brown, smooth, and hairless. Young twigs have
scattered white lenticels (air pores) and depressed leaf scars. Leaves
occur oppositely or in whorls of 3; they tend to hang downward
from the twigs. The leaf blades are 6-12" long and 4-8" across; they
are cordate to cordate-ovate in shape and smooth along their margins.
Sometimes a leaf blade may have a pair of shallow obtuse lobes. The
upper surface of the leaf blades is yellowish green, light green, or
medium green and hairless (or nearly so), while the lower surface is
more pale and short-pubescent. The petioles are 4-6" long, light green,
and either hairless or mostly hairless.
This tree produces erect pyramidal panicles of flowers about 4-12"
tall and nearly as much across; there is typically 10-30 flowers per
panicle. Individual flowers are 1½-2" across and 2-2½" long; each
flower has a broad tubular corolla with 4-5 frilly lobes, a calyx that
is deeply divided into 2 lobes, a 2-celled pistil with a white style, 2
long fertile stamens, and 3 short infertile stamens (staminodia).
The corolla is bright white overall; it has purple-dotted lines and
patches of bright yellow along the lower surface of its throat.
The lobes of the calyx are oval-ovate, light green to purple,
either hairless or finely pubescent. The branching stalks of the
panicle are green and hairless. The blooming period occurs from late
spring to early summer, lasting about 2 weeks. Individual flowers
remain in bloom for only a short time; they have a pleasant fragrance.
Afterwards, fertile flowers are replaced by narrowly cylindrical
seedpods that are 10-18" in length and about ½" across; they are either
straight or slightly curved, and droop downward from short stalks.
Immature seedpods are green, while mature seedpods are dark brown.
During the fall and winter, the seedpods slowly divide into 2 parts,
releasing their seeds. The seeds are arranged in conjoined pairs with
outer fibrous wings; they are covered by a papery membrane that is
light brown. Each pair of winged seeds is about 1-2" long and ¼" (or a
little more) across. Individual seed bodies are about 5 mm. long and 4
mm. across, oval in shape, and flattened; their tips are well-rounded,
rather than pointed. The pairs of winged seeds are very light and
easily blown about by the wind. The root system is relatively shallow
and spreading. The large deciduous leaves become pale yellow or pale
greenish yellow during the autumn.
is full or partial sun, moist well-drained conditions, and fertile soil
that contains loam or silt-loam. However, this tree will adapt to other
situations that are less ideal. Northern Catalpa develops quickly,
particularly while it is young, but its longevity is short (typically
about 50 years). The twigs and
branches are somewhat brittle and can be
damaged by wind and ice storms. Because of the large leaves, abundant
large flowers, broken twigs and branches, long seedpods, and winged
seeds, this tree produces abundant ground litter.
Northern Catalpa is an uncommon tree in natural
areas; it is
native to southern and southeastern Illinois, while in other areas of
the state it has escaped from cultivation (see Distribution Map).
Originally, this tree was native to a small region of the
Habitats include mesic woodlands, moist floodplain and bottomland
woodlands, moist woodland openings, higher ground in swamps, powerline
clearances in moist wooded areas, railroad clearances in moist wooded
areas, woodland borders, edges of yards in suburban areas, and
urban parks. Areas with a history of disturbance are preferred. This
tree continues to spread in areas outside of its original range. It is
often cultivated as an ornamental landscape tree.
Associations: The flowers of Northern Catalpa are
bumblebees (Bombus spp.),
the Large Carpenter bee (Xylocopa
and various moths that are primarily nocturnal visitors. Other floral
visitors include honeybees (Apis
mellifera), skippers, ants, and flies,
but they are less effective at cross-pollination. These insects usually
obtain nectar from the flowers. This tree also has extra-floral
nectaries on its leaves, which secrete nectar in greater amounts than
normal when the leaves are damaged. This attracts such predacious
insects as ants, ladybird beetles, and parasitoid wasps, which feed on
nectar that is easy to access. It is thought that such insects help to
protect this tree from various insect pests that feed on the leaves.
These pests include the caterpillars of Ceratomia catalpae
Sphinx) and Xylophanes
tersa (Tersa Sphinx), the larvae of Contarinia
catalpae (Catalpa Midge), the aphids Aphis citricola and
persicae, and Pseudococcus
comstocki (Comstock Mealybug); both the
aphids and mealybug are highly polyphagous.
Birds and mammals
apparently make little use of the leaves or seeds of this tree as a
food source. However, when little else is available, rabbits and small
rodents will gnaw on the bark of saplings. Sometimes the broken-off
branches and trunks of older trees
develop cavities that are used as dens by tree squirrels and other
small mammals, or they are occupied by Screech Owls and other
cavity-nesting birds. Robins and other birds sometimes
build nests in the branches.
Location: Chief Schemauger Park and Crystal Lake Park in
Northern Catalpa is one of two species in this genus that occur in
Illinois -- the other species, Catalpa
bignonioides (Southern Catalpa),
is native to a fairly small region of southeastern United States, but
not Illinois. This latter species is also cultivated throughout the
state as a landscape tree and it occasionally escapes. Distinguishing
these two species is rather difficult as they both have similar leaves,
flowers, and seedpods. The following characteristics can be used to
distinguish Northern Catalpa from its more southern sibling: 1) its
crushed leaves do not have an unpleasant scent, 2) its flowers are
slightly larger in size with fewer purple spots, 3) it tends to have
fewer flowers per panicle, 4) it has slightly longer and
wider seedpods, 5) for mature trees, its trunk bark
is more furrowed, and 6) both tips of its seeds are blunt, rather than
pointed on one side. Unfortunately, there is some overlap in many of
these characteristics. In the past, the wood of Northern Catalpa was
to make rail ties and fence posts because its wood is resistant to
moisture and decay. Today, it is cultivated as an ornamental landscape
tree. The two trees in this genus have a very distinct appearance and
can't be confused with anything else.