Tree · Bignoniaceae
Northern Catalpa
Catalpa speciosa
A tough native tree hung with showy white flowers and broad heart-shaped leaves that grows fast almost anywhere.
Full sun
Every 7–21 days
USDA 4–8
40–70 ft · 12.2–21.3 m
Overview
Northern catalpa carries some of the largest leaves of any hardy tree, broad heart-shaped blades that can span a hand and more, soft and a little coarse to the touch. In late spring the crown fills with showy white flowers, each bloom shaped like a small orchid with a frilled throat marked in faint yellow and purple. The flowers gather into upright clusters that stand out against the green.
By fall those blossoms give way to the tree's oddest feature: long, slender seed pods that hang down like thin beans or cigars, often well past a foot, drying to brown and splitting to release papery winged seeds. The pods dangle in loose bunches, which is how it picked up names like cigar tree and Indian bean tree. The bark of an older trunk breaks into shallow scaly ridges over a pale, fast-grown wood.
Up close the wood itself tells the story of the tree's speed. It is light, soft, and brittle, so twigs and limbs snap rather than bend, and the big leaves tear easily along their veins in a strong wind. The whole tree reads as oversized and loose-limbed, with coarse texture from the wide leaves down to the chunky pods.
Care
The short version: this broad-leaved, fast-growing tree takes full sun to part shade and almost any soil, wet or dry. Once established it rarely needs feeding or extra water, so the real work is pruning the brittle young wood for strong structure and giving the wide-spreading crown and its falling limbs and litter room to clear patios and walks.
Light
Catalpa colors and flowers best in full sun, and it tolerates part shade. Strong light packs the crown with more of the orchid-like blooms and thickens the canopy of broad leaves into a denser, sturdier head, while a shaded tree grows looser but still healthy.
Water
An established tree, with its deep coarse roots, rides out both seasonal flooding and drought, so it rarely needs watering. Young trees want regular moisture through their first year or two while those roots push down. The top half of the soil should dry between waterings.
Soil
Few trees root as willingly into difficult ground. Catalpa prefers a moist, fertile loam dark with organic matter, yet it sinks its roots just as well into heavy clay, soggy low spots, dry poor dirt, and packed urban soil.
Temperature
Catalpa is cold-hardy and heat-tough, holding its broad leaves across USDA zones 4 to 8 and weathering a range from -29°F to 100°F (-34°C to 38°C). Once it is rooted in, temperature is rarely something to manage.
Humidity
Ordinary outdoor humidity suits the foliage fine, so there is no number to meet. Air moving through the crown matters more, since open airflow dries the wide leaf surfaces and keeps the leaf-spot and mildew fungi from filming over them.
Feeding
This adaptable native rarely needs feeding to keep its leaves full and green. A single balanced, general-purpose tree fertilizer in spring covers it if the growth looks thin and the foliage pale, and most years it can be skipped.
Pruning
Catalpa is pruned in late winter to early spring to cut out dead, weak, or crossing branches and to train a single strong central leader. The pale wood is brittle and snaps clean, so shaping the young limbs early builds the sound branch unions the tree needs for life.
Repotting
Catalpa is a large landscape tree, not a pot plant, so repotting rarely comes up. A young one held in a container is moved up when the roots coil around the inside, push out the drainage holes, or water runs straight through.
Size & spacing
This is a big, broad tree, its trunk lifting a wide head to 40 to 70 feet (12 to 21 meters) tall and spreading 20 to 50 feet (6 to 15 meters) across. The crown needs plenty of open room, well clear of buildings, walks, and power lines.
When to plant
Catalpa is set out in spring after the last frost, or in fall. The white flower clusters open in May and June, each orchid-like bloom flaring from the leafy crown, and the long slender pods lengthen behind them through summer until they hang well below the foliage.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring; seed needs no special pretreatment.
- Plant: Spring after the last frost, or in fall.
- Harvest: Showy white orchid-like flower panicles in late spring to early summer (May to June), followed by long bean-like seed pods.
Hardiness
USDA hardiness zones: 4–8
Temperature: down to -34°C
Troubleshooting
Most of what marks a catalpa shows plainly on the leaves, the wood, or the pods, and most of it is cosmetic rather than serious. The exception is verticillium wilt, which has no cure and hides inside the wood. The close signs below help tell one from another before any treatment.
Leaves drooping fast as one side browns and dies back
This is verticillium wilt, a soilborne fungus that creeps up inside the wood and chokes off its water channels, with no chemical cure. Cut into a wilting branch and the wood beneath the bark shows brown or greenish streaks running through it. The affected limbs are pruned out, the tree is kept well watered to hold its vigor, and a susceptible species is not replanted in that soil if the tree dies.
Fix:
- Prune out and dispose of affected branches
- Keep the tree vigorous with proper watering, as there is no chemical cure
- Avoid replanting susceptible species in the same soil if a tree dies
Jagged broken limbs and leaves ripped ragged by a storm
Catalpa wood is pale and naturally brittle, so wind, ice, and hail snap limbs clean off and shred the wide leaves along their veins. After a storm the crown shows broken or hanging branches, which are pruned off with clean cuts. Training young trees to one strong central leader, and siting them where falling limbs clear patios and walks, keeps the brittle wood from causing harm.
Fix:
- Prune cleanly to remove broken or hanging limbs
- Develop a strong central leader and good branch structure with early structural pruning
Leaf blades gnawed to the stem, the crown left skeletal
The feeder is the catalpa sphinx caterpillar, the catalpa worm, a striking larva that eats only catalpa. They cluster on the leaves and can chew a tree down to bare twigs in mid to late summer, leaving the big blades reduced to ragged midribs, yet the tree pushes out fresh leaves and recovers. Look for fat caterpillars with black heads, a black stripe running down the back, pale sides, and a slim black horn at the tail. Anglers prize them as fish bait.
Fix:
- Handpick caterpillars from small trees, or simply tolerate them since trees easily re-leaf
- Harvest them as fish bait, for which catalpa worms are prized
- Apply a labeled caterpillar control such as Bt or a recommended insecticide only for heavy infestations on small or young trees
A powdery white film or inky dark blotches on the blades
These are powdery mildew and leaf spot fungi, which film the broad leaves white or freckle them with dark blotches, sometimes with twig blight that withers small shoots. Heavy mildew yellows the leaves and drops them early, but the damage stays on the surface and rarely needs a fungicide. The fallen leaves are raked up and removed, and the crown is opened to move air across the foliage.
Fix:
- Rake and dispose of fallen infected leaves
- Improve air circulation
- These foliar problems are largely cosmetic and rarely require fungicide
Toxicity
Catalpa is not toxic. It never appeared on the ASPCA poison-plant lists, and the long bean-like pods, for all their odd look, are inedible but not a poisoning hazard. The one physical caution is the foliage, whose surface can leave sensitive skin a little itchy, so gloves help for a big cleanup.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
Catalpa is not on the ASPCA toxic list, so a curious cat batting at a fallen pod on the ground is in no danger.
Dogs Safe
There is no poisoning hazard for dogs. One that gnaws a stray pod may get a mild stomach upset from the fibrous bulk, but the tree itself is not toxic.
Horses Safe
Catalpa holds no known toxin for horses and is not on poison-plant lists, so the foliage is safe near them.
Rabbits Safe
The broad leaves and long pods hold nothing toxic to rabbits, so a nibbled leaf is harmless.
Livestock Safe
Sheep, cattle, and goats can feed around the tree unharmed, as catalpa is not a known poison for grazing stock.
Birds Safe
Neither the leaves nor the elongated pods do birds any harm.
People Safe
The tree is safe to be around, though the pods are inedible and the leaf surface can leave sensitive skin a little itchy, so gloves help for a big cleanup.
The long seed pods and large leaves create heavy litter, and the foliage can cause minor contact dermatitis in sensitive people, so wear gloves when handling.
Varieties
A few catalpas show up in plantings, and the differences are written in the leaves, the scent, the flowers, and the shape of the crown. These are the ones worth knowing by name and by their close-up details.
Catalpa speciosa (Northern catalpa)
The larger, hardier of the two main species, tall and upright in habit, with green-scented leaves and the cold-tolerance to hold down through zone 4.
Catalpa bignonioides (Southern catalpa)
A smaller, more rounded tree whose foliage gives off a fetid scent, with flowers freckled more heavily in purple that open a touch later in the season.
Catalpa bignonioides 'Nana' (Umbrella catalpa)
A dwarf, non-flowering form grafted onto a standard trunk, its dense twiggy growth forming a rounded umbrella of a head.
Catalpa bignonioides 'Aurea'
A golden-leaved selection whose foliage glows a bright yellow to yellow-green.
How to propagate
Catalpa multiplies readily, whether from the flat winged seed shaken out of its long dry pods or from a cutting struck off the soft new wood of an existing tree.
SeedEasy
Collect seed from the long bean-like pods in fall and sow in late winter to spring. · 1 to 2 seasons
Seed is the simplest route. The flat, papery winged seeds are shaken from the long dry pods in fall and sown from late winter into spring, with no soaking or chilling needed first. They sprout readily into broad-leaved seedlings, and because the tree grows so fast they fill out to landscape size within a season or two.
Stem cuttingsModerate
Softwood cuttings in early summer or hardwood cuttings in the dormant season. · 1 season to root
Cuttings work as well, taken as soft green wood in early summer or as firm dormant wood in winter, rooting in about a season. Pieces of root strike too. Named forms like 'Nana' are grafted rather than rooted from cuttings, since they do not come true on their own roots.
Myths
The catalpa worm strips every leaf from the branches until the tree dies.
The catalpa sphinx caterpillar can chew a tree down to bare twigs, but it flushes a fresh set of leaves and comes through fine, even after the same stripping happens several years running. The defoliation looks alarming but does no lasting harm, so it rarely needs any response.
The long, bean-shaped pods will poison a pet.
Catalpa never made the ASPCA toxic-plant lists and counts as non-toxic. The long pods are inedible but not a poisoning hazard for cats or dogs, for all that they look like giant beans.