Experimenting with Canarians 2: Sonchus acaulis

One of my most hated enemies in the garden is sow thistle (Sonchus oleracea). It is an annual or biennial weed that is brilliantly adapted to survive in gardens. It starts as a small rosette of leaves, especially of germinating in Spetember, lying flat against the soil, gradually increasing in width. It is very obvious at this stage but has a really strong root so that even if you bunch up the leaves so you have a good grasp of it, pulling rarely removes it, just leaves the dishevelled and partially leafless plant behind to grow again. It is largely a plant of disturbed and cultivated soil because of this rosette habit – it can’t compete with lots of vegetation, but it can seed into small cracks in paving where there is no competition. Then, when your back is turned, it starts to grow upwards, into a large, leafy, rather succulent plant. You may spot it, seemingly a week later, when it is 30cm high. You bend down, grasp it at the base of the stem and… snap. The stem comes off and leaves the base behind to resprout. Or you may not spot it for three weeks when, if you have good soil, it will be 1m high. If you have sown your rows of annuals or carrots the seedlings do not bother so much with the rosette phase and just run straight up, making gorgeous, soft plants that will smother your seedlings – nothing grows faster.

And before you know it, you have lots of bright, dandelion-like flowers that hardly seem to have closed before they pop open as silky seeds heads. The good news is that, although called thistles, these are rarely prickly, though some species are better armed than others, so be careful before thrusting your hand in among them.

They are perfectly designed to be efficient, with hollow stems to minimise construction materials and maximise strength. They have a milky sap and I remember we used to feed them to our tortoise. I am sure they must be edible in some form – perhaps the flower buds can be pickled or added to salads. I have never tried, but I can’t believe that something so lush is completely inedible. And aphids love it, along with leaf miners – they can’t all be wrong.

So it may seem odd that my object of desire today is a sow thistle. But this is not an ordinary one, it is a species from the Canaries.

In these, and other isolated islands, plants do odd things and Sonchus acaulis is one of the odder ones. Acaulis means ‘’without a stem’ and this species grows as a large rosette of leaves for several years before sending up a tall flower stem from the centre. It is a growth pattern that is common in harsh, island environments and I find it fascinating that so many, unrelated plants, have all come to the same conclusion as a way to survive; take several years building up a head of steam and then put all your efforts into a huge inflorescence and make lots of seeds all in one season and then die. It seems a very risky strategy. It is found in argyroxiphium in Hawaii, puyas in South America, giant lobelias, giant cabbage trees and the echiums of the Atlantic islands. I am no evolutionary botanist but perhaps, because the habitats are so specialised and the individual plants so uncommon, only if a plant produced a spectacular display of flowers would pollinators see them. After all, an echium flower is individually very small and might be missed, but pack thousands of them on a spike 4m high and even the most myopic bee would be bound to find the flowers.

But this sonchus is not quite so exaggerated and does not live in the hostile conditions endured by Echium wildpretii on Teide, it grows on steep rocky slopes, often in shade and sometimes on north-facing rocks and always where there is plenty of water. It does not grow in drought conditions with Canarian euphorbias and the toughest aeoniums, though it does grow with other, green aeoniums. I found lots in the Anaga peninsula, in the cool, moist laurel forests of Tenerife (top pic). But I grew some from seed collected (legitimately and paid for) in Firgas in Gran Canaria. I was keen to grow them, partly because I have been to Firgas. It is known for its volcanic water that is sold across the Island and I have posted before about the village and its tiled seats (search for Firgas in the bar to the right). This is curious since some references say that this species is endemic to Tenerife. Anyway, two years ago I sowed the seeds.

They came up well and I soon had a dozen plants in cell trays. The problem was that this is not a hardy plant (probably – though I am going to experiment) and I was building a house and didn’t have anywhere to plant them. So I potted some up and some, sadly, expired through neglect. But I ended up with four and last autumn one was put into the bed at work in the greenhouse after I lifted the tomatoes. More or less frost free but not heated, the soil is good but it has not been fed. And while the other three are sitting in their 10cm pots, making rather pathetic rosettes 25cm across the one that was planted out has gone BONKERS.

Like my previous post about pericallis, the obvious lesson I have learned is that just because a plant comes from an island where some areas are hot and dry, it does not mean that everything from there loves drought. And because winters there are likely to be mild and wet it means that the plants are likely to grow in winter, when conditions are better than in the hot, dry summer.

We know this because of Viburnum tinus. Try as I might, I can’t hate this rather dull evergreen shrub and the reason is because of its resolute determination to flower in winter. We might think this is rather daft but it is simply because it is from the Med. And there in summer it is too dry for growth so it does its flowering and growing in the mild, moist winter. Of course, transplanted here, it does not realise that our winters are too cold for many bees to be buzzing around and it still opens its buds in the forelorn hope that the weather might be decent for a day or two.

So my sonchus has steadily grown into a rosette 2m across with beautiful, jagged leaves a metre long. It is intriguing how the ordinary can seem extraordinary when closely observed and I love to see the fine toothing of the leaves every day. It is just an overgrown lettuce at the end of the day but I have admired its speed of growth and structural muscularity. And then, a month ago, something stirred in the centre of the leaves. A head of buds, cocooned in white hairs, ascended from the crown and is now 1.2m high. Clusters of knotted white buds are slowly separating on stout stems, ready to open into large yellow ‘flowers’.

I have often said that we would value dandelions if they were rare and difficult to grow and here is the proof.

I can’t wait to see the flowers, even though I know the plant is then going to die. And the other three will be put into the garden this spring to see how they fare, on my north-facing bank below the hedge, as close as I can get to its wild habitat. At least I should have lots more seed to experiment with.






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3 Comments on “Experimenting with Canarians 2: Sonchus acaulis”

  1. tonytomeo
    February 20, 2020 at 8:11 am #

    Okay. . . now, that looks a bit intimidating, like a Super Sowthistle! So many plants from the Canary Islands are odd like that, like enhanced versions of what is ‘normal’. Canary Island pine – Canary Island date palm – Algerian ivy.

  2. Paddy Tobin
    February 22, 2020 at 8:03 pm #

    I cannot overcome my distaste for sow thistle to welcome even such an exotic character from the Canary Islands – it would ever be a sow thistle in my eyes. I look forward to see your photographs of it when in flower.

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