Gardening: The Northern Catalpa

God writes the Gospel not in the Bible alone, but also on trees, and in the flowers and clouds and stars. – Martin Luther 

Catalpa speciosa, up close and personal. Photo: Mean and Pinchy, Flockr ccl

Can you believe this is a flower on a tree? I suppose, horse chestnut does look kind of the same, but to me these resemble some sort of Azalea or Rhododendron. They’re absolutely beautiful. It’s a shame the flowers don’t last longer than they do.

Photo: carlfbagge, Flickr ccl

The blossoms you are looking at are from the Catalpa tree and those blooms are usually gone in about one week. Catalpa speciosa is a genus of flowering plants in the trumpet vine family, Bignoniaceae, that grows in the warm temperate regions of North America, the Caribbean, and East Asia. A tree that’s a member of a vine family… how interesting.

Catalpa goes by many other names including northern catalpa, hardy catalpa, western catalpa, cigar tree, and catawba-tree. It is native to Arkansas, Illinois, Indiana, Missouri, Kentucky, Pennsylvania, and Tennessee in the US. Because of its hardiness it is also used north of the border in Canada. Catalpa speciosa is hardy to USDA Zones 4-8.

In Halifax (Zone 6) there are a few places where Catalpa has actually been planted as a street tree. Those trees were in flower about two or three weeks ago. They’re quite a stunning thing to stumble across on a walk. I can only imagine what a grove of them would be like.

The seed pods hang beneath the leaves. Photo: pcgn7, Flickr ccl

Description

Catalpas are medium-sized deciduous trees, which mean they loose their leaves in the Autumn. The bark is brownish grey with hard, raised ridges. The leaves are quite large and heart shaped, some being in excess of 12” long. 

The leaves don’t really colour much in the Autumn. If they do it’s only because the frost has hit them and then they turn yellowy brown.

The flowers are about 2-3” across, very white with yellow and purple stripes and dots. They're somewhat reminiscent of the interior of a Foxglove. The flowers are borne in panicles of between 10 to 30 individual blooms. It’s quite a show. And after the blossoms come the “beans!” 

The fruit of the catalpa resemble vanilla bean pods on steroids. They begin green and purple, turning to brown as the seeds inside mature. They can easily grow between 10" and 16” long. For added ornamental display, they dangle beneath the leaves. Inside the pods are packed with numerous flat seeds surrounded by a papery “wing.”

The trunk and branches tend to grow crooked.
Photo: Rebecca - Lee, Flickr ccl

Uses

Catalpa is usually grown as an ornamental tree. It prefers moist, high pH soil and full sun, but has been able to grow almost anywhere in North America that it has been planted.

The wood is soft like white pine, and quite light in weight. It also is resistant to rot. In the 1920s and 30s Catalpa was encouraged as a quick growing source of fence posts in some southern States of the USA. They soon learned in warmer conditions it can be a little invasive. 

It is more commonly used now in the production of furniture and interior house items, due to its beautiful grain. 

Drawbacks

Northern Catalpa does have some less than serious issues. My feeling is if you can deal seasonally with an apple tree, you can deal with a catalpa.

Catalpa doesn’t really like the idea of growing straight. If being grown for lumber, this makes sawing a challenge. 

The second problem is all those seeds and blossoms. The spent blooms tend to flutter away (like the apple), but the long pods open up while still on the tree and blow seeds to the four winds, making clean-up a bit of a chore. The seed pods then dutifully drop from the tree so you have to clean them up as well. 

The third is it’s penchant for fast growth which is why they were grown in the South in the 1920s. A mature Catalpa can easily crowd out, and shade, other plants in smaller gardens so leave room for its full size.

Photo: lowjumpingfrog, Flickr ccl

This last problem I haven’t seen in practice here. The street trees in Halifax seem to hover around 20 feet high by about 15 wide. That's a manageable size for a tree with blossoms as beautiful as these.

Catalpa are a gorgeous specimen and bloom at a most opportune time. Early August in Nova Scotia is a time when all other blooming trees are well on their way to bearing fruit. So the Catalpa could be a good specimen plant to ensure mid-Summer garden enjoyment.

Just try finding it in a garden centre… That’s possibly the most troublesome aspect of this beautiful tree. This year I’m going to collect seeds – again...

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