Acanthus spinosus

I took today's Botany Photos of the Day one morning a few weeks ago in our Physic Garden, an area that usually hums with the frenzied activity of elated honeybees. On this particular summer morning, when the sun took a rare break behind a blanket of cream-coloured cloud, things were somewhat more silent, serene, and, it seems, congenial to contemplation.

Acanthaceae is a family of 250 genera and about 2500 species that put forth perfect (bisexual) flowers along with alternately arranged leaves that are simple and decussate. Member species are typically herbs, shrubs, or vines that produce two-leaved (e.g. dicotyledonous) seeds. The family—which receives its scientific name from the Greek akantha (prickle or thorn) for its characteristically spiky leaves and flowers—is native to a broad variety of habitats throughout the tropical regions of Malaysia, Africa, Central America, and northern South America, though some genera and species are native to more temperate climate areas.

Acanthus, a genus of 30 species, is native to the Old World, where its distribution is centered around the Mediterranean Basin. One of these species, Acanthus spinosus or bear's breeches, is a self-sowing evergreen perennial hardy to climate zones 5 through 9. At altitudes below 800 metres, the plants grow to just over 1 metre in height, and they spread to about a ½ metre when sited in full sun or partial shade and exposed to moderate amounts of water. The species enjoys dryer soils, and is often found in olive groves and alongside roadways, though it is commonly cultivated as a garden ornamental as well. The hooded flowers, which bloom from June to August, are a deeply veined purplish grey.

The plant, whose somewhat mysterious common name derives from its broad and hairy leaf, is included in our Renaissance Physic Garden because, to use the words of the contemporary (16th century) English Botanist John Gerard, the plant was at one point thought "an excellent plaister against numbness in the hands and feet".

Physic Garden Plant1
Physic Garden Plant1

14 responses to “Acanthus spinosus”

  1. Sarah D

    What a great garden-worthy plant this is – I grow it at the base of a high wall in my south facing chalky garden in central England. It looks lush and healthy all summer. But be warned: the inflorescences are iron-hard and I keep scratching my car on them – yes, they are that hard! So different from A. mollis.
    Great site! It cheers my day to open your emails.

  2. Bonnie K.

    The stylised design of the acanthus leaf was used to decorate the capital (top) of columns built in the Corinthian style by the Greeks and Romans.

  3. Tessa

    Can you explain what the climate zones mean, please?
    Where would the UK figure in the system?

  4. Ann Rein

    Thank you for posting this – I’d seen this plant up at Cornell Plantations in the Robison Herb Garden this past weekend, but forgot to write down which species it was. They have a lovely if not formidable looking stand of it!

  5. Angela Dianne

    These are beautiful, mysterious plants with a great contrast of colors and textures. I saw them growing wild, like weeds on the grounds of some of the ruins in Athens, Greece. This is the flower that was used in ancient times to make the crown that can be seen on Greek sculptures. Wonderful photography, thanks.

  6. Mary Ann, in Toronto

    What an interesting plant. I’d love to see one of these in person. Some more great photos of it are here:

  7. Tree Zed

    Zones are used to help gardeners in North America know if a certain plant will grow in the region where you reside. It lets us know how cold hardy (the main issue for Canadians) and how heat tolerant (more for the Americans down South) a plant is. Zones go from 1 to 11.
    The higher the Zone number the milder the winters are required and the more heat a plant can tolerate.
    Living in Zone 5, this means I can only grow plants that are rated Zone 5 and lower if I want them to survive the winter. I can only tell you that I often feel rather envious of those gardeners living in more temperate zones (they get grow so many more plant species than me). In the summer, I can grow a Zone 6,7 or 8 plant with no problems, but I would not expect it to survive the winter. A perennial for people living in those zones, would be an annual for me (ex. petunias).
    Hope this helps.

  8. Vi Stapel

    I wonder I had a long line of what I thought was a type of Rhubarb in South Africa that was perennial and only died down once a year.
    It had very similar flowers that very prickly and lasted long when cut and dried.
    They bloomed once a year and huge green leaves (that I not see on your photo) They grew over 10 years faithfully embellishing our driveway.
    It would be great to see the foliage of this gorgeous plant. Thank you.

  9. Mary Ann, in Toronto

    Vi, try the link I entered, 3 posts earlier. One of those photos shows foliage. Click on the thumbnail to see an enlargement.
    Or do an image search with google, using the scientific name.
    Enter “Acanthus spinosus” (without quotation marks), into the “exact phrase” box here:
    You’ll have 10,000 images to peruse to your heart’s content. And lots of foliage.

  10. Cambree

    Another pretty purple & white flower I’ve never seen before.
    And what a fuzzy buzzy bee. Great photos!

  11. Emma

    Does anyone know how to get rid of them? They are growing in abundance in my garden. Any suggestions greatly appreciated!

  12. elizabeth a airhart

    fine photos thank you
    i live in florida and the usda prints a
    zone map and i go the bbc garden page uk
    lots of information on thier web site
    i take the eden project newsletter etc
    rhs also has lots of info
    the botanical gardens of birbingham ala
    has a big website is a free garden
    books give your libarary a try even
    the young peoples section may have
    the basics and this wonderful page

  13. Sam G

    WRT Zones, I think a picture is worth a thousand words:
    It’s specific to North America, but I’m sure you can get a good idea where you would fit in based on your “remembered” winters.

  14. Sue

    Dear Emma,
    I have been looking for these plants for a long time and you are trying to get rid of them?!?! If you are in the US I really would be delighted to buy some from you. I first saw these plants in Australia in a friends garden. She also considered them to be extremely invasive. I know you have to dig deep to get up all of the roots and cut the flowers down before they seed. She did this for a couple of years and won her battle. Please let me know!

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