Pseudofumaria alba – Corydalis ochroleuca
Pseudofumaria alba, the plant formerly known as Corydalis ochroleuca, is a beautiful, but unassuming, little plant, which surprises you when it pops up unexpectedly in just the right place. However, it is also a plant that is taken for granted, a plant that is often overlooked, a plant that is, dare I say, sometimes thought of as a weed.
But I have found some interesting, some might think, exciting, information about it. Read on to find out more.
I changed horses midstream – but I think it turned out well
My plan was to write a post about dicentra, a great favourite of mine at this time of year. Soon after starting my search for information, I found a book that looked as though it would be really useful for my research. Thanks to an online second-hand bookseller, a copy of Bleeding Hearts, Corydalis, and their relatives was soon in my possession and was just what I needed. The three co-authors bring their expertise in the taxonomy and cultivation of these plants and present it in a most readable and interesting way.
It answered a lot of my questions about dicentras but I became sidetracked and fascinated when I reached the part about the plant that I had always known as Corydalis ochroleuca. I decided to take this path, away from the planned route, and see where it took me. I can always return to the main road another day.
Let’s deal with the name – Pseudofumaria alba
The genus Corydalis has had three species removed from it. (Corydalis sempervirens was renamed Capnoides sempervirens but does not concern us here.) We are interested in Corydalis lutea and C. ochroleuca, which are now named Pseudofumaria lutea and P. alba. Why has the name been changed? The book I referred to seeks to explain.
The author acknowledges that name changes can be disquieting for gardeners but suggests that botanists usually have good reasons for renaming a plant. If a species has been misidentified, it needs correcting, and new information might require a name change. In this case, the changes reflect a better understanding of evolutionary relationships.
Our two species were removed from Corydalis because morphological characteristics show that they are not directly related to the remaining species of Corydalis. This was later confirmed by DNA sequences. There is a difference in the styles – in Corydalis they persist in fruit, but in Pseudofumaria they quickly fall off. The Pheudofumaria flower has a short, rounded spur, whereas in Corydalis this feature is much longer. These traits, together with the presence of small bracts, show that Pseudofumaria is instead closely related to Fumaria.
Pseudofumaria alba has also had a change of species name as well as genus. This is because the name alba was validly published earlier than the name ochcroleuca so has priority under the rules of botanical nomenclature.
Do we care? As gardeners, probably not. Until, that is, we want to communicate with others about it. Then we certainly need to know which plant we’re talking about. The RHS, on their website and in Plant Finder, and most nurseries and seed suppliers in the UK are sticking with Corydalis. Scientists and academics, who are trying to achieve classifications that reflect evolutionary relationships, are going with Pseudofumaria. Maybe, we just have to be aware that there are two names in use and we might come across either one depending on where we look.
There is also some dispute as to which family they belong, Papaveraceae or Fumariaceae, so perhaps we’ll leave taxonomy there and get on with finding out what the plants actually look like.
Pseudofumaria alba as a garden plant
Pseodofumaria alba is a short-lived perennial native to northwestern Balkans and northern Italy, where it grows on cliffs and rocky outcrops. It has become naturalized throughout Europe as a garden escapee, often growing on walls.
It is easily cultivated but can be difficult to establish. However, once you do manage to get it going, you will never be without it. Self-sown seedlings can be left to develop if they put themselves in a suitable place, where they are not wanted they can easily be removed. They can seed themselves in walls, between paving, and other interesting places where you wouldn’t have thought of planting them. You might get a pleasant surprise!
Pseudofumaria alba prefers well-drained, neutral to slightly alkaline soil and is happy in either a sunny or shady site. It is hardy to -25˚C and will grow to about 30cm high and wide. Books tell me that it is evergreen but, I have to admit, I haven’t taken much notice once they have finished flowering. I will definitely look more closely this year and see if it’s the same plants that persist or new seedlings that reach flowering size.
Now we can take a closer look at the detail.
The leaves are like filligree
Pseodofumaria alba has hairless, juicy, extremely brittle stems, dull pink in colour, and delicate leaves reminiscent of maidenhair fern. They are tripinnate with leaflets deeply cut into lobes, pale green with a glaucous covering on both surfaces. Here you can see a young, newly opened basal leaf and a more mature one. Leaves, without petioles, are alternate and spirally arranged along the stem.
The inflorescence – from bud to open flower
The inflorescences grow from the leaf axiles. They are terminal with six to sixteen flowers arranged in a loose raceme.
You can see the tiny buds just emerging from between the sepals. They are white with a green patch and grow but remain closed. Eventually, the flowers open.
Now we can go in even closer.
The Pseudofumaria alba flower in wonderful detail
Each flower is just 17 mm long, held on a 10 mm pedicel, which has a small bract at its base. The flower is zygomorphic, so has one plane of symmetry. There are two sepals, which, if I’m not being too fanciful, remind me of seashells. The flower has four petals, two outer and two inner or lateral. The outer petals are white with some yellow shading and winged at the apex. The upper one extends into a short, rounded basal spur, which contains the nectary. The lateral petals are white with deep yellow tips and they are fused at these tips, blocking the flower’s entrance and hiding the stamens and style.
Now for the interesting bit
This was what grabbed my attention when I read it. I was amazed that such a tiny flower would have such an intricate pollination mechanism and was fascinated to find out if I could see how it worked.
The flower of Pseudofumaria alba has two bundles of stamens and the filaments are fused throughout their length. The style ends in a single stigma. When the flower is still in bud, protuberances at the edges of the stigma interlock with the anthers. As the flower matures, the stamens are pulled downward and pollen is deposited on the stigma. This is all hidden inside the fused inner petals.
Almost all species in Fumariaceae have a constriction at the middle of the inner petals, which acts as a flexible joint. But Pseudofumaria is different. Its inner petals are only unilaterally indented, rather than fully jointed, the lower margin being continuous and rather firm. This makes their distinct method of pollination possible.
The end of the embrace
The inner petals and the style-stamen arrangement are held under tension so that they try to move in opposite directions. They are prevented from doing so by flaps on the inner petals that embrace the style and stamens. When an insect visits, the style with its pollen is released from the embrace in a sudden and irreversible movement, transferring pollen to the bee. The style and stamens end up resting against the upper petal. However, this process can only happen once and, despite this elaborate mechanism, Pseudofumaria alba is self-compatible.
I decided to try to see this for myself but could not find a flower that had been visited. Perhaps the cold, wet weather at the time discouraged flying insects. I then wondered if I might pretend to be a bee and achieve the desired effect. I pressed down very gently on the inner petals and – ‘ping’! You can see the result in the image. Absolutely amazing!
Ants enter the story
As the flowers fade the seed pods form and ripen very quickly. The seeds are attractive to ants and they aid their dispersal. I have often read an explanation along those lines but never wondered exactly how and why the seeds are attractive and how ants disperse them. Until now.
Seed dispersal by ants, myrmecochory, is very common in plants in the Fumariaceae. They have fleshy, white, fat-rich appendages, elaiosomes, attached to their seeds, which are very nutritious and attractive to ants. The ants carry or drag the seeds to their nests, where they remove the elaiosomes and feed them to the colony’s young. The seeds are then thrown out of the nest and left to germinate and develop into the next generation of plants.
I have seen photographs of seeds with elaiosomes so decided to take a look to see what I could find. These seeds are about 1mm across and you can see the jelly-like elaiosomes and the deeply-textured seedcoat. Isn’t that incredible?
Pseudofumaria alba – a lowly plant with a fascinating back story
A lowly plant, yes, some might even describe it as ordinary but I wouldn’t like to be without it. And now I know so much more about it, I hold it in higher esteem. Once again I have learned a lot from my investigations so I’m glad to have found this plant’s hidden depths.
A close relative
If you would prefer something with a bit more colour, you might like Pseudofumaria lutea, the only other species in the genus. It is native to the southern foothills of the Central and western European Alps, where it grows on cliffs and rock outcrops. As a garden escapee, it is distributed more widely across Europe than P. alba. It is also a more commonly cultivated and slightly more vigorous species. The biggest difference is that P. lutea has yellow flowers, otherwise it is very similar to P. alba.
Find some useful information
Bleeding Hearts, Corydalis, and their relatives by Mark Tebbitt, Magnus Lidén, and Henrik Zetterlund. This is the book from which I gleaned most of the information in this post. I’m looking forward to finding out more on other plants in the same family.
Myrmecochory – Wikipedia A very informative article about seed dispersal by ants. (Search for a browser extension called Wikiwand to enhance the Wiki content.)
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