At the Northwest Perennial Alliance’s Study Weekend in 2018, Jimi Blake’s slide of this plant reminded me of seeing this plant growing in the San Francisco Botanic Garden in Golden Gate Park. It was a standout and prompted me to immediately start looking for it. Annie’s Annuals carries it and I discovered that it was a zn 9b plant, cooling my ardor somewhat…still…..I returned a couple years later to the Botanic Garden, rekindled my interest and made a stop at Annie’s on our return trip to home, but it wasn’t available, so it went back to my wish list. Then Jimi’s presentation at the Seattle Study Weekend moved it up in the queue.
I am most familiar with the species of Sonchus that are weeds. I have pulled more than my share of Annual and Prickly Sow Thistle, Sonchus oleraceus and S. asper, but like many genera Sonchus contains several plants of horticultural merit. Most Sonchus are annual species, a few are perennial and fewer still are ‘woody’ species all of which occur on the Canary Islands alone, like Sonchus palmensis.
There are 19 different species of ‘woody’ Sonchus on the Canary archipelago. Five of the seven islands contain at least one of these species as a local endemic. Fuerteventura, the closest of them to Africa, is around 60 miles from Morocco, and is the oldest of them at nearly 21 million years. The islands are spread along a line westerly, each having arisen volcanically, each one younger than those to its east, the most westerly, El Hierro, forming less than a million years ago. Genetic researchers believe that based on their studies, these woody Sonchus species are all descendants of a single colonization event which then spread from island to island in a process of speciation and radiation. Genetically, the plants are very close especially when compared to other flowering plant genera and this is consistent with the isolation found on smaller islands around the world. It is interesting to note that eight other species are also closely related, but are within other genera. A few of these can be found on the island of Madeira, about 250 miles north of the Canary Islands and the Cape Verde Islands, an archipelago about 350 miles off of the coast of Africa and nearly 1,000 miles SW of the Canary Islands. All of these have taken a very similar evolutionary pathway, though their forms and the environment within which they naturally occur, are sometimes quite different. This group forms what is recognized as the Woody Sonchus Alliance. Such alliances are fairly common on archipelagoes.
These remind me of the ‘woody’ Tree Lobelias that are endemic to the Hawaiian Islands, an alliance of 125 species including several genera. There, Lobelia are thought to be amongst the earlier plant arrivals and through a similar process of speciation and radiation evolved into the unique and diverse species we see today, in their cases, several of which are threatened.
Sonchus palmensis is endemic to the the single island of La Palma, which at only 1.5 million years is the second youngest of the seven Canaries. Three other members of the Alliance can be found there. It occurs around the entire island growing at elevations between 600′ and 3,300′, often on quite steeply sloping and rocky terrain, though its most commonly found on the eastern side. Pictures will show this growing out of rock piles suggesting that they will want very good drainage. Because they are quite common on La Palma they are listed as ‘of least concern’ by the IUCN.
The foliage is very similar in form to that found growing around the rosette of our local annual Sow Thistle, on this species forming leaves closely attached to one another near the terminals of each branch, giving the plants what some would term their gawky appearance and others would describe as ‘Dr. Seussian’. The stems grow up to 6′ tall, branching irregularly on mostly bare stems. At flowering, a many branched inflorescence forms at the terminal carrying typical Asteraceae heads often described as ‘Dandelion like’, each floret, including all of the center disk florets, being ligulate with their two fused elongated petals and three diminished ones.
The climate on La Palma is very mild, sub-tropical oceanic, with a winter/mediterranean pattern of rainfall. Temperatures are remarkably consistent around the year. La Palma the youngest, most westerly island, is less influenced by the heat of the African continent than are the other, nearer islands. It more mountainous with very little flat plateau area and consequently is wetter across the majority of its surface than the other islands. Overall this is the ‘greenest’ of the seven islands. Keep in mind that while most of the rain is received in winter months, fog and heavy clouds often form around the mountains during summer, both cooling and adding moisture through condensation. Sonchus palmensis occurs in the often fog-shrouded Heath-Pine Forest where Pinus canariensis is predominant, as well as along roadsides. P. canariensis is very important ecologically to this biome as it receives about 20″ of rainfall annually, the Pines capturing enough condensate from the fog to effectively increase this 4 times! greatly benefiting the flora and local economy in the process. Scattered through this and below to lower elevations where Laurel forests predominate are Erica spp. like Erica arborea and E. scoparia. There are many different plant communities on these diverse islands which, like many archipelagos have a high rate of endemism.
This can be grown well outside in the Bay Area with its moderated summers. Sonchus, as a group, will grow best in full sun and are tolerant of summer drought conditions though S. palmensis may be more dependent on regular water than the other species. In California, Sonchus canariensis, is considered to be drought tolerant. Understand that this latter species is native to Gran Canaria and Tenerife, both more easterly, warmer and drier. These are considered to be hardy to zn 9b, down to 25ºF, some suggested colder, as one might expect coming from the Canary Islands where it can rub plant ‘shoulders’ with other natives like several Aeonium spp., Echium wildpretii and several Euphorbia spp. Last summer, ’19, our summer highs were moderate for us, but we had a record number of lows over 60…and my S. palmensis stressed in its pot and mostly defoliated…this one may have a tendency to go summer dormant with heat.
How many zn 9b plants does one need in a zn 8b garden? Well, for me it depends on its gifts, what it offers the garden and how it measures up to the other plants I’m already growing that require me go the extra mile. This plant brings a lot to the garden table. For now it goes into the queue. This will take our summer heat in Portland. I can picture growing it successfully on my front porch in a large pot where it will be shaded from the hottest part of the day, late afternoon…and it goes without saying, in a well drained mix with regular summer water! It would add a touch of humor to my xeric front garden with its strong architectural form looming from on high.
Sonchus canariensis is another choice member of the Alliance. Check out this page on the Strange Wonderful Things.
Thank you for all you have written. I did endings a few years back and purchased a Giant Dandelion from Annie’s some years ago and placed it front and center in the garden. It grows now to about 14 feet tall. This year has five giant bundles of flowers. I was curious if you have any idea if the plant is edible? I have been thinking about making a dandelion honey from the flowers. I haven’t been able to find any info on this elsewhere Thanks!
A couple things, I would never suggest to anyone to take some person’s suggestion to eat a non-food plant. Tree Dandelions are in the same family as that of Taraxacum officianale, the common weedy Dandelion, the Aster family. Sonchus is a different genus and may contain different chemical compounds. Ask a reputable source knowledgeable of the your plant’s ethnobotany, it’s use by native people if any. No reason to take an unnecessary risk.
I saw this beautiful plant blooming at the SF botanical gardens this week, and it was incredible. I did a search and your post was the first one I looked at.
Thanks for all the info!
I have a very happy S. palmensis in coastal Southern California. It receives direct sun for part of the day, with regular marine layer to bring that dampness this plant seems to love.
I bought it in a 5 gallon pot about a year and a half ago, and it has grown quite a bit since. Around the fall/winter, I do tend to pick off a sizable amount of dried dead leaves, restoring its sunning sculptural character.
Does anyone know about the possibility of taking cuttings off of S. palmensis? I’ve recently tried taking a few and will let you know how it goes.
I can’t answer your question. My spotty memory seems to recall receiving my plant from Annie’s, that it was a stubby rooted cutting, but I’m not sure and I know nothing of their process. I have germinated several seeds from my plant and my am growing them on in my basement, but they aren’t looking good at present.🙁
Hmmm….I wonder if it has a summer dormancy in situ? I didn’t read anything that suggested such. The Canaries do have a mediterranean climate with dry summers and many parts of them are drier overall than we are though S. canariensis tends to occur most often on eastern facing slopes, morning sun, not the hottest locations. I haven’t seen a map of preferred areas, but one source says they tend to occur in barrancas, or steep ravines where they may be even more protected and shaded from the afternoon sun. On Tenerife the summer high temps seem to average close to ours as they are moderated by the surrounding ocean. You grow yours in a pot, which will increase the soil temperature in summer. 85ºF seems to be a cut off for a lot of plants in terms of conditions under which they best grow…above that and their metabolic processes may be disrupted. I wonder if the summer deciduousness your plant experiences is a heat response?
S. palmensis comes from the island of La Palma, further west, further from the continental effect of Africa, and with both milder temperatures and significant moisture even in summer from cloud condensation….I wonder if all of these do better in maritime climates? Or, would they perform better planted in the ground here, during summer, shielded from the highest temps with cooler roots, and then dug in the fall for winter protection? Plants that have C3 and CAM photosynthetic metabolisms are better adapted to hot and dry conditions.
Two other ‘random’ observations, one of the pictures I posted shows an Aeonium growing near the base of a Sonchus palmensis. Aeonium do better for me protected from the hot summer sun. Perhaps them growing together suggests they would both prefer that. Also, when I see pictures of Echium spp. growing in the wild there they seem to occur on more exposed, drier, sites, these don’t seem to be companions though they are both Canary Islands resident endemics.
Just an FYI that my Sonchus canariensis goes dormant in the summer, reliably, every year. Don’t know that a S. palmensis would be the same but it’s something to consider if you’re planning on it being a summer star. Mine looks great right now, and will look it’s very best in the early springtime. Come July and August it’s just a pretty, branched, stick.