Catalpa, Catawaba, tree

How to Grow a Catalpa or Catawba tree

Catalpa flowers

You may know it as catalpa, Catawba, Indian Bean, Cigar tree, or Fish Bait tree but chances are if you live in the United States, you have seen this unique tree.  Catalpa is a true tree of the people, surviving in all kinds of conditions from polluted cities to windswept prairies.  Native Americans utilized the Catawba long before settlers arrived in the New World.  But the settlers soon recognized the value of the catalpa and carried it with them across the country.  With catalpa’s ability to survive most conditions and grow rapidly, and it’s bonus of beautiful, fragrant flowers, it was the pioneer’s choice of trees to plant on a new homestead.

For fast shade in rough conditions, catalpa is a good choice.  Farmers plant catalpa for the wood, which makes strong, lightweight, rot-resistant fence posts.  It makes a nice specimen tree with showy flowers at a time few other trees are blooming.

There are two recognized species of catalpa or Catawba tree in North America, Southern Catalpa, C. bignonioides, and Northern Catalpa, C. speciosa.  There are only subtle differences in the two and they have both been planted far outside their natural ranges.  Both catalpas are hardy in Michigan to zone 4, both have large, heart-shaped leaves, fragrant white flowers splashed with yellow and purple, and long skinny seed pods resembling bean pods. The Southern Catalpa is a slightly smaller tree, with the leaves growing in a whorled pattern rather than opposite each other as in the Northern Catalpa.  The leaves of some Northern Catalpas may be lobed.  Catalpa ovata, Chinese Catalpa, is a small tree, with lobed leaves.  The creamy yellow flowers are also a bit smaller, and produced later in the summer.  They are hard to find.

The white flowers of the Northern and Southern Catalpa tree are large, frilly and orchid-like.  They are marked with purple dots and yellow patches, no two seemed to be marked quite alike.  When catalpa trees bloom in June or July, the sweet scent of the flowers can be almost over powering.   Bees, butterflies and hummingbirds flock to the flowers.  It’s quite a show for a week or two, and then all of the flowers are shed, making the ground under them look like a summer snowfall has occurred. The flowers turn into purple, then green, and then brown narrow pods, up to a foot long.  They may hang in the trees all winter. In the fall or following spring the pods release hundred of flat seeds.  If birds do not eat them they turn into more catalpa trees in every corner of the yard.

The catalpa tree is slow to leaf out in the spring, but when it does, it produces a deep shade. The leaves of catalpa are large, up to a foot long in some cases.  Usually they are medium green, slightly lighter and downy on the underside.   Purple and golden leaved varieties exist. 

Catalpa culture

While catalpas seem to pop up everywhere when you have a tree in the yard, the seeds seem to be a little tricky to germinate.  If you cannot find a small catalpa tree to purchase and have access to seeds, sow them in an outside bed of well-prepared soil in late fall or very early spring, cover lightly, and let nature do the work.  Catalpas transplant fairly easily when small.  Catalpas will grow almost anywhere, in any kind of soil, but they need full sun and fairly regular moisture.  They will not grow in poorly drained areas.  They grow quite rapidly when young.   A catalpa tree in a good spot may add 2 foot of growth a year and trees bloom young, as early as six years of age.

Catalpa trees do have some disadvantages in the home landscape however.  Severe winters, like the winter of 2014-15 can cause a lot of dieback on catalpa including limbs on large trees, but the trees usually recover.  The trees are messy, shedding flowers, large leaves, and seed pods abundantly.  Some people are allergic to the pollen of catalpa flowers and the scent really bothers some sensitive people.  In the south catalpas are also host to large green and yellow caterpillars in great numbers, the larvae of the Catalpa Sphinx moth, the reason for one of catalpas folk names.  Many a southern fisherperson has planted Catawba trees just to get the bait worms.  But for other folk these caterpillars are a big disadvantage, raining down green droppings and defoliating the trees. They can be controlled with insect sprays when they first hatch.  These worms have not been a problem in Michigan.

Catalpa trees often become infected with verticillium wilt, a fungal disease that causes large parts of the tree to die.  Catalpas tend to shoot up suckers from the roots, and side shoots from the trunk, and few ever totally die, but they look unsightly and need constant trimming of dead areas.  There is no real cure, but fertilizing with a high nitrogen fertilizer helps the tree keep growing.  If you remove the tree, don’t replace it with another catalpa tree in the same area as the disease remains in the soil.

If people in the household frequently suffer from seasonal allergies, a catalpa tree might not be a good landscape choice, as the flower pollen is quite allergenic.  The roots of catalpa are poisonous, but don’t seem to cause the problems with other plants that walnut roots produce.  The sawdust from working with catalpa wood can cause inhalant and skin allergy symptoms.  For that reason it would probably not be good to use catalpa wood chips or shavings as animal bedding.  The seedpods and seeds of catalpa contain a mild narcotic and sedative and should not be put in the mouth or consumed.