Wednesday Weed – Indian Bean Tree

Photo One by geograph-5810580-by-Jaggery

Indian Bean Tree (Catalpa bignoniodes) in Monmouth (Photo One)

Dear Readers, I was so taken by the Indian Bean Tree (Catalpa bignoniodes) that I found growing in St Olave’s Court in the City of London last week that I thought I’d investigate a bit further. This is a magnificent street tree, with its enormous leaves, striking bean pods and extraordinary flowers, and you may sometimes see the golden-leaved cultivar ‘Aurea’, which adds another element to the tree’s attractiveness with its lemon-hued foliage. It is such an unusual plant that I can’t believe I’ve never paid it any attention before. Apparently the bean pods are sometimes used by children as a sword/light sabre substitute, and I can see why.

Indian Bean Tree ‘Aurea’, showing off those beans (Public Domain)

Indian bean trees, or catalpas, come originally from the southern states of the US, and one of their alternative names is ‘cigar tree’. The photo above shows why. The name ‘catalpa’ might derive from the Muskogee word ‘kutuhlpa’, which means ‘winged head’ – inside the beans are winged seeds which will spin away in a breeze to find a new growing site. Once landed, the trees seem to have a habit of spiralling towards the light, leading to some very eccentric growth patterns. I noted last week that the tree that I saw seemed to be determined to reach the small window of sunshine between the buildings that surrounded it, and some other images show the same determination.

The Indian bean tree in St Olave’s Court

Photo Two by By Jean-Pol GRANDMONT - travail personnel, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3633275

An Indian bean tree in the private gardens of Louvignies castle in Belgium (Photo Two)

The main reason for planting this tree is, however, for its flowers. Goodness. They appear in July, and I shall have to put a date in the diary to remember to go and look. If I told you that one of the closer relatives of the catalpas is the house plant incarvillea, I’m sure you wouldn’t be surprised. The first Indian bean tree is said to have arrived in the UK in the eighteenth century, brought here by Mark Catesby, who published the first ever guide to the natural history of the Americas between 1729 and 1747.

Photo Three by By Le.Loup.Gris - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15730180

Catalpa flowers (Photo Three)

Photo Four by Epibase [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Incarvillea delavayi ‘Snowtop’ (Photo Four)

But what really intrigues me about the Indian bean tree is that, most unusually, it produces nectar in its leaves. I mentioned this in my original post, but something about it had me scratching my head. Producing nectar is expensive for a plant, which is why it is usually a way of attracting insects for pollination, so why would this tree ooze sugar from the veins in its foliage? I had to dig a bit, but a reason finally appeared.

The Indian bean tree’s leaves are the only food of the caterpillar of the catalpa sphinx moth (Ceratomia catalpae). The larvae can completely strip a tree of its leaves, sometimes several times per year. It can be so damaging that the first ever trial of aerial crop dusting was an attempt in 1921 to get rid of the caterpillars from a catalpa farm. The jury seems to be out as to whether the insects actually cause long-term harm to the tree, with some people arguing that the frass from the larvae is such a good fertilizer that on balance the Indian bean tree is not harmed, and others saying that they regularly give their tree a good hose down to stop the worst depredations of the ‘catawpa worm’.

Photo Five by By Patrick Coin (Patrick Coin) - Photograph taken by Patrick Coin, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=643830

Catalpa sphinx moth (Ceratomia catalpae) (Photo Five)

Photo Six from CC BY-SA 2.5, https://en.wikipedia.org/w/index.php?curid=12702147

Catalpa sphinx moth caterpillars munching on Indian bean tree leaves (Photo Six)

However, the tree is not without help. Enter the bodyguard ant (Forelius pruinosus). A 2003 study by J.Ness showed that when the caterpillars attacked a catalpa, it started to produce the nectar from its leaves. This in turn attracted the ants who not only enjoyed the sweet treat, but turned their attentions to the caterpillars. Hence, the depredations of the moth were not as bad as they might have been. When in balance, nature seems to have an answer for everything.

Incidentally, the caterpillars are a great favourite as bait for anglers, and in some parts of the US catalpa trees are planted just so that the ‘worms’ can be harvested and used to catch catfish.

Fortunately in the UK we don’t (yet) have the catalpa sphinx hawkmoth, so I think those lovely big leaves are safe for the moment.

The wood of the Indian bean tree was once used for fencing and for furniture making. The tree is sometimes now planted in areas of soil erosion, because the roots can help to hold the soil together, and historically the tree was often planted as a shade tree, close to the house. The huge leaves provide shelter and shade for birds too, although I’m not sure how far they eat those catalpa caterpillars – the tree produces a chemical which will deter most herbivores, and these substances are often bitter and unpleasant, so maybe the caterpillars don’t taste so good.

Photo Seven from https://commons.wikimedia.org/wiki/File:Catalpa_bignonioides,_from_The_natural_history_of_Carolina..._Wellcome_L0047451.jpg

Baltimore orioles sheltering beneath the leaves of an Indian bean tree, from ‘The Natural History of Carolina, Florida and the Bahama Isles’ by Mark Catesby (1683 – 1749) (Photo Seven)

The beans and bark have been used as a cough medicine and to reduce the symptoms of asthma, and a distillation of the fruit has been used as a cure for conjunctivitis. The roots, however, are very poisonous.

And now, a poem. While the Indian bean tree is very beautiful, many US websites also describe it as what might politely be called ‘a pain in the backside’. The flowers drop off and turn to mush, the beans do the same, occasionally whole branches crack and hang, the leaves are either eaten by catalpa worms or fall and make the paths slippery. And yet. John Ciardi (1916-1986) seems to sum up the dilemma in his poem ‘The Catalpa’, which is not just a consideration of this tree, but of what price we put on the beauty of a moment.

The Catalpa

The catalpa’s white week is ending there
in its corner of my yard. It has its arms full
of its own flowering now, but the least air
spills off a petal and a breeze lets fall
whole coronations. There is not much more
of what this is. Is every gladness quick?
That tree’s a nuisance, really. Long before
the summer’s out, its beans, long as a stick,
will start to shed. And every year one limb
cracks without falling off and hangs there dead
till I get up and risk my neck to trim
what it knows how to lose but not to shed.
I keep it only for this one white pass.
The end of June’s its garden; July, its Fall;
all else, the world remembering what it was
in the seven days of its visible miracle.
What should I keep if averages were all?

 

Photo Eight By Magnus Manske - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7398450

Indian bean tree flower (Photo Eight)

Photo Credits

Photo One by geograph-5810580-by-Jaggery

Photo Two by By Jean-Pol GRANDMONT – travail personnel, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3633275

Photo Three by By Le.Loup.Gris – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15730180

Photo Four by Epibase [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Photo Five by By Patrick Coin (Patrick Coin) – Photograph taken by Patrick Coin, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=643830

Photo Six from CC BY-SA 2.5, https://en.wikipedia.org/w/index.php?curid=12702147

Photo Seven from https://commons.wikimedia.org/wiki/File:Catalpa_bignonioides,_from_The_natural_history_of_Carolina…_Wellcome_L0047451.jpg

Photo Eight By Magnus Manske – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7398450

 

20 thoughts on “Wednesday Weed – Indian Bean Tree

  1. Sarah

    A lovely tree! I’ve noticed recently how parakeets seem to love them. I’ve watched them in Kensington Gardens and Kew Gardens crunching up the long ‘beans’.

    Reply
    1. Bug Woman Post author

      Those parakeets certainly have varied tastes, don’t they – I’ve seen them eating crab apples, sweet chestnuts and picking the flowers from cherry trees.

      Reply
      1. Sarah

        Yes! I was impressed watching them eat sweet chestnuts at Kew – skilfully opening the prickly husks and extracting the chestnuts. From the aerial walkway you can watch them do it just a few feet from your face. And this week I’ve had them on my garden feeder eating RSPB seed mix.

  2. FEARN

    I was intrigued by this tree a couple of years ago when visiting Prague. Nice to learn a bit about it. They also had, I think, the Black Locust Tree Robinia Pseudoacacia in Peace Square but I don’t know if they grow in London. (I haven’t seen either in Scotland.)

    Reply
    1. Bug Woman Post author

      We do have black locust in London, and also the honey locust (Gletitsia tricanthos) – the heat island effect means that we have a variety of trees that won’t survive in colder climates. And you’ve given me some ideas for yet more Wednesday Weeds 🙂

      Reply
  3. Gibson Square

    There was once an Indian Bean Tree on the A12 dual carriageway at Wanstead. Unfortunately this was removed with the road’s upgrade. But at least I can see a wonderful specimen of this tree outside St. Margaret’s Church on Parliament Square.

    Reply
  4. gertloveday

    What a beautiful tree. I looked to see the potential for planting one in the Southern part of Australia but it came with a warning to check with the council to see if the tree is regarded as a weed.

    Reply
    1. Bug Woman Post author

      Ah, interesting – I sometimes watch a TV programme about Australian border controls, and am impressed with how stringent the staff are about the importation of biological materials like food and plant materials. I can’t see anything online about it being prohibited though?

      Reply
  5. Anne Guy

    I have a multi stemmed purple Catalpa and two Aurea trees which I pollard each winter to keep them small in our garden, The two aurea ones i actually grew from a seed pod I found lodged under my windscreen wiper when I used to park in the student car park at the horticultural college! I noticed that this parent tree had recently been felled after falling in a storm but happily my pollarded ones continue the line! Love these trees. Actually I guess because we pollard ours they don’t always flower but have had years when they do…lovely sweet smelling blooms.

    Reply
  6. tonytomeo

    What an odd species to import to England. I know it is pretty and all, but there are so many better trees. They were imported here with the migration of the Okies, and are delightful shade trees. They self sow, but not enough to become naturalized. Because the sphinx moths did not migrate with them, they neither defoliate through summer, nor produce foliar nectar. The problem is that they grow so fast and develop structural deficiencies. Some are disfigured by limb failure or renovative pruning in response to such failure. Most do not last longer than thirty years or so. I think they last longer in Oklahoma because they do not grow so fast, particularly in the wild.

    Reply
    1. Sarah

      We have some splendid big specimens in the UK, certainly older than 30 years. Perhaps they don’t grow fast enough to develop structural deficiencies here.

      Reply
      1. tonytomeo

        That would make sense. I saw some relatively old specimens in Oklahoma that were only beginning to deteriorate. There were some in Oklahoma City that were supposed to be quite old. It seems like I read about this species in England before, as if it is a well regarded tree there. People really like them here too, but it is not a tree I recommend without explaining their personality.

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