The Catalpa Tree: The Unique “String Bean” Tree

If you’ve ever stumbled upon an unusual tree with dangling bean-like seed pods you’ve likely encountered the Catalpa. This distinctive tree is easily identified by its long, slender fruit that resembles green beans, earning it the nickname “string bean tree”.

Beyond its ornamental pods, the Catalpa tree has a number of other notable features. It is valued for its hardy timber abundant flowers wildlife benefits and resistance to pollution. Though relatively short-lived, Catalpas make beautiful additions to large properties and parks.

Curious to learn more about this unique tree? Keep reading for a complete overview of the Catalpa – the string bean tree.

Catalpa Tree Key Features

Catalpas belong to the Bignoniaceae family and are classified as Catalpa speciosa in the northern states and Catalpa bignonioides in the south. Here are some key identifying features

• Leaves: Large, heart-shaped leaves up to 8 inches long arranged in whorls of 3

• Flowers: Showy spring flowers borne on panicles up to 8 inches long. Flowers are bell-shaped with white and purple spotted throats.

• Fruit: Slender, bean-like pods 6-24 inches long that hang vertically from branches

• Bark: Light grey and smooth when young, becoming furrowed with age

• Height: 40-70 feet tall with an oval, open crown

• Lifespan: Typically 50-60 years, sometimes up to 100 years

The Origins of the Catalpa Name

The name Catalpa has its roots in the Cherokee language. It comes from the word “kutuhlpa” which means “winged head” referring to the winged seeds inside the long pods.

The species name speciosa is Latin for “showy” or “beautiful” in reference to the attractive flowers. Other common names for the tree include cigar-tree, catawba, Indian bean tree, Hardy Catalpa and Western Catalpa.

The Catalpa is sometimes confused with the more tropical Paulownia or Princess tree, which has similar leaves andflowers, but lacks the long fruit pods.

Native Range and Growth Habitat

The Northern Catalpa is indigenous to a relatively small region of central Mississippi River basin from Arkansas up through Missouri, Illinois and Indiana. It has been widely propagated beyond its native range thanks to its hardy timber and abundant blooms.

Catalpas prefer full sun exposure but tolerate partial shade. They thrive in moist, fertile, well-drained soils and have good wind and drought tolerance. They can adapt to a range of soil pH but prefer slightly acidic conditions. Catalpas grow well in most temperate climates including USDA hardiness zones 4-9.

Catalpa Flowers and Seed Pods

One of the Catalpa’s most ornamental features is its spring flower display. Clusters of showy, bell-shaped white flowers with yellow and purple spotted throats appear in mid to late spring after most trees have finished flowering. The fallen blooms create a dramatic white carpet effect on the ground.

These large panicles of flowers give way to the Catalpa’s signature long, slender seed pods in early summer. Starting out bright green, the bean-like pods eventually turn brown by fall. They hang vertically from branches, gracefully swaying in the breeze.

Inside the pods are rows of flat winged seeds. The pods split open when ripe, releasing the seeds to be dispersed by the wind.

Uses for Catalpa Wood

Catalpa wood is lightweight, straight-grained, relatively soft and resistant to decay. This makes it valued for the following uses:

• Fence Posts – One of the most common historical uses due to its rot resistance and light weight. Freshly cut posts can be used without treatment.

• Railroad Ties – Catalpa wood is still used for railroad ties in South America due to its durability.

• Fuel – Catalpa burns slowly with little smoke and makes excellent firewood.

• Pulp – The wood fibers are useful for making high quality paper products.

• Art Carving – Catalpa’s soft, easily worked texture lends well to detailed carving and whittling.

• Interior Trim – Adds visual interest when used for decorative millwork, cabinets, doors and trim.

Catalpa Tree Benefits

Beyond ornamental interest and timber uses, Catalpa trees provide additional benefits:

• Shade Tree – Its broad canopy provides ample shade. Leaves filter sunlight creating dappled shade.

• Wildlife Habitat – The nectar-rich flowers attract hummingbirds, bees and butterflies. Songbirds eat the seeds.

• Pollution Tolerance – Its adaptability and vigorous growth allow Catalpas to thrive in urban areas and resist pollution.

• Fast Growth – Catalpas are exceptionally fast growing when young, upwards of 3 feet per year. Their rapid growth quickly provides shade and screening.

Potential Drawbacks of Catalpas

The Catalpa’s messy fruits and weak branching habit create some negatives:

• Short lifespan of just 50-60 years typically

• Brittle, prone to storm damage

• Bean pods and large leaves require cleaning up

• Susceptible to leaf spots, powdery mildew and leaf miners

• Taproot makes transplanting older trees difficult

• Can be invasive as seeds spread aggressively

How to Grow Catalpa Trees

Catalpas grow best in full sun locations with well-drained, fertile soil. They have higher moisture demands when young but become quite drought tolerant when mature. Here are some tips for growing Catalpa trees:

• Purchase young nursery-grown saplings in spring.

• Select a spot with plenty of room to accommodate mature size.

• Plant in spring after the last frost.

• Space multiple trees at least 20 ft. apart.

• Keep soil moist but avoid waterlogged conditions.

• Apply general purpose fertilizer in early spring.

• Prune to shape structure and remove dead branches while young.

With its tropical-looking beans dangling from every branch, the Catalpa tree is one of the most distinct specimens you can grow. Beyond the ornamental seed pods and plentiful blooms, it provides wildlife support, hardy timber and pollution tolerance. Though relatively short lived, Catalpas bring beauty and shade to yards small and large. Just be prepared to clean up some litter in exchange for this fascinating tree.