Denise Ellsworth

We were dreaming, and it was a pleasant dream: an old yellow farmhouse, yellow barn and a few outbuildings, plus mature apple trees and a raspberry patch. The driveway was lined with towering catalpa trees in full bloom. Spent flowers tumbled to the ground like giant flakes of summertime snow.

My husband John and I could imagine living here, sitting on the wrap-around porch, drinking our morning coffee and planning out the day. Should we weed the garden, repair the electric fence, or plant the new peach trees first?

The property was for sale, and the asking price was (almost) affordable. Affordable, if only nothing would ever need repaired or maintained for as long as we lived. Paint the barn? Repair the plumbing? Replace tiles on the slate roof? A pool of expendable cash equal to the asking price would be needed just to keep up with a spread like this.

Suddenly the dream twisted into a scene from The Money Pit, as we watched our lovely farmstead flake and crumble around us. We would be house rich and supply poor, unable to keep up with the constant deluge of repairs and replacements.

Brought back to reality, we paid for a few trinkets at the barn sale, took a last wistful look around and made our way back to the car. But those catalpa trees: That memory stays with me.

Few gardeners plant catalpas these days, but historically they were staples on the farm, in large part due to the rot-resistant wood used for fence posts and railroad ties. The yellow farm’s huge catalpas towered over the driveway, where they had probably been growing for decades.

The Northern catalpa (Catalpa speciosa) is native to the Ohio River valley and south, but has been widely planted outside of its range. An adaptable, fast-growing tree with useful wood, Northern catalpa can mature to 70 feet or more in height if the site is right. The name catalpa comes from the Muscogee word kathulpa which means “head with wings,” possibly referring to the fringed flowers or the papery fringed seeds.

Also known as Indian bean or cigar tree, catalpas are covered in white flowers in early summer that later give way to long, curling brown pods that resemble curling, skinny bean pods. Large, spreading branches create a rounded crown. Heart-shaped leaves, up to 12 inches long, adorn the coarse branches, sometimes tattered by wind or hail.

The Southern catalpa (Catalpa bignoides) is a smaller tree, generally maturing under 40 feet in height. Blooming later than its Northern cousin, Southern catalpa blooms around the time of the littleleaf linden. The flowers on both Northern and Southern catalpa are white and tubular with ruffled edges. The center of each flower is marked with yellow dots and purple lines. Borne in panicles of a dozen or so flowers, the sight of catalpa in bloom can be impressive. The floral display lasts for about two weeks.

Although both species of catalpa are sometimes used in urban or street settings, these trees aren’t ideal for urban or landscape use. While the wood is rot-resistant, branches are brittle and can break considerably in wind and ice storms. Seed pods, fallen flowers and masses of fallen leaves in autumn are messy to clean off streets and sidewalks. Still, some cities (including Chicago) recommend the Northern catalpa for use as a street tree.

On a recent visit to southern Ohio to speak about pollinators, I was struck by the sight of so many catalpa trees in full bloom in parks and along roadsides. At Cox Arboretum in Dayton, bumblebees and carpenter bees worked catalpa trees in bloom. These bees are attracted to the flowers’ fragrance and bright white petals marked with yellow dots. The bees are then guided into the flower by the purple markings, also known as nectar guides, to help them find their reward.

Catalpa flowers are self-infertile, meaning a pollinator is necessary for cross-pollination and the development of seed pods. While honeybees will visit catalpa for nectar, they are too small to successfully pollinate the flowers.

Scientists in the 1970s determined that catalpa flowers target their nectar offerings depending on the time of day and the resulting pollinators.

During the day, flowers produce nectar with a higher sugar concentration than at night, but the total quantity of nectar produced at night is higher. Daytime pollinators — bumblebees and carpenter bees — make ready use of this concentrated nectar. At night, moths visit the flowers, sucking up nectar with their long coiled tongues.

This makes perfect sense if you imagine using a long straw to drink in either apple juice or maple syrup. Drinking either would be fairly easy with a short straw (or mouth part), but the maple syrup (with its higher sugar concentration) would be much harder to drink through a long straw.

To tailor their offerings to day and night visitors, catalpa flowers have evolved the strategy of changing their reward to meet the needs of both types of pollinator. As many as 15 species of moths have been observed visiting catalpa trees at night.

Besides the nectar produced in the flowers, catalpa offers nectar on the leaves in what are known as extra-floral nectaries. These nectaries produce more nectar when leaves are damaged, attracting ants, lady bird beetles, predaceous wasps and other natural enemies. The insects are attracted to the sugary reward, then do the work of helping to protect leaves from pest insects.

Catalpa doesn’t have a large number of pests, but the Southern catalpa in particular can be attacked and sometimes completely defoliated by the catalpa sphinx caterpillar. These large caterpillars gather and feed en masse on catalpa leaves. Some individual catalpa trees may be repeatedly attacked year after year, while a neighboring tree remains virtually untouched. Most trees seem able to recover from caterpillar defoliation with little lasting effect. The caterpillar is seldom seen in our region of Ohio.

Interestingly, catalpa sphinx caterpillars are prized by fishermen in the Southern U.S. The caterpillars’ tough skin, aroma and wiggling activity make them a sought-after natural bait. Fishermen will even freeze collected caterpillars, or pickle them in corn syrup for later use.

To tell the Northern and Southern catalpa apart, crush a leaf. Southern catalpa has an unpleasant odor. It also blooms several weeks later than Northern catalpa. Both trees have large leaves arranged in a whorl on the branch, with three leaves attached at a node. This whorled characteristic is obvious in winter by looking for the sunken leaf scars that resemble suction cups.

Denise Ellsworth directs the honeybee and native pollinator education program for Ohio State University. If you have questions about caring for your garden, contact her at 330-263-3723 or ellsworth.2@osu.edu. Her blog is at https://u.osu.edu/thebuzz.