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BLADDER SENNA

Colutea arborescens

Pea Family [Fabaceae]

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category
category8Shrubs
category
category8Deciduous
category
category8Broadleaf
status
statusZalien
flower
flower8bicolour
flower
flower8yellow
inner
inner8orange
morph
morph8zygo
petals
petalsZ5
stem
stem8round
toxicity
toxicityZmedium

20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
A popular ornamental garden shrub growing up to 4m high.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
1-Pinnate leaves with 7-13 pairs of leaflets, plus a terminal one. Seed pods inflate when ripening.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
Large yellow pea-type flowers.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
Leaflets broad and elliptical and somewhat glaucous green.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
Flowers yellow with two fine orange loops near the centre of the banner, which is the largest of the five petals.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
A large re-curved banner with two narrow wings hiding the two keels within.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
Loop markings reminiscent of those of some Orchids.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
The seed pods start off green but inflate with some gas to become very bulbous and reddish.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
The sepals of the flowers are now more visible when the petals drop off as the pods ripen.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
Highly inflated reddish pods. They are filled with some gas; the seeds within occupy far less volume than that provided. Remains of petals, now fawn, above the pods. The pods will become papery thin and fawn when the seeds within are ripe.


20th July 2013, Leeds & L/pool Canal, Bootle, Merseyside. Photo: © RWD
Leaflets virtually hairless. Stems reddish.


26th Aug 2016, park garden, Waterloo, Sefton Coast. Photo: © RWD
Your delinquent Author tore the thin membrane (which is in 2 halves) into two to reveal the two rows of 'peas' in the bladder pod. They are not edible!


26th Aug 2016, park garden, Waterloo, Sefton Coast. Photo: © RWD
The 'peas' themselves are pale-green and slightly flattened and kidney-bean shaped. Peas are strictly speaking the fruit contained within the pod. Each pea contains seeds. Deep within you can just espie some 'failed' 'peas'. Peas which are green are immature, as are these.


26th Aug 2016, park garden, Waterloo, Sefton Coast. Photo: © RWD
The 'failed' peas in close-up.


Easily semantically confused with : the Genus Senna [which although belonging to the same Pea (Fabaceae) family, are not Senna plants but look fairly similar and the flowers, although yellow, are a totally different shape]

Not to be semantically confused with : the Genus Cotula [plants belonging to the Buttonweeds Genus (in the Asteraceae family)]. Nor with Bladder Campion (Silene vulgaris) which belongs to another differing family, the Pink & Carnation Family (Caryophyllaceae)

Easily mistaken for : Orange-bladder Senna (Colutea × media) [being the hybrid between Bladder Senna and the non-native Colutea orientalis]. Orange-bladder Senna differs from Bladder Senna in that the flowers are an orange-bronze colour with a beaked keel and the pods which split open at the apex.

Uniquely identifiable characteristics

Distinguishing Feature : The inflated seed pods are a feature of all Bladder-sennas, of which there are about 25 species worldwide. However, only the two mentioned above escape into the wild in the UK.

Like many plants from the Pea family Bladder Senna contains some quinoliziding alkaloids such as Cysteine, which is poisonous if consumed. It also contains the poisonous Canavanine, a non-proteinogenic amino acid (NPAA) which is similar to the amino acid L-Arginine.

The shrub is popular in gardens as an ornamental due in part to the unusual and eye-catching highly-inflated seed pods which are filled with a gas. Others say they are filled with a liquid.

Some sources claim that the gas within the seed pods is air, but this seems unlikely seeing as it seems to be pumped inside by the plant, and would probably have an excess or a deficiency in some gas compared with the relative concentrations of the gases which constitute air. Your Author would imaging that carbon dioxide concentrations were anomalous compared to those of air and it might even have some ethylene gas as well, a well known plant hormone produced by some plants. Of course, these gases would eventually diffuse out until it did have the same proportions of gases to those constituting air. If they were initially filled with a liquid, it could be that as the liquid evaporated within the pod, this inflated the pod because gases occupy about 2000-times the volume of liquids, which would neatly explain how the pod becomes so bloated, which is otherwise hard to explain.

The shrubs escape in the UK and are to be found naturalised in waste or grassy places, on railway embankments and beside roads mainly in the home counties but elsewhere scattered about in the UK south of Newcastle.


  Colutea arborescens  ⇐ Global Aspect ⇒ Fabaceae  

Distribution
 family8Pea family8Fabaceae

 BSBI maps
genus8Colutea
Colutea
(Bladder-Sennas)

BLADDER SENNA

Colutea arborescens

Pea Family [Fabaceae]