Beware the Beloved Scottish Thistle

Lee Royer
Frederick County Master Gardener

Scotophiles everywhere adore their native thistle. Scottish children learn the story of the thistle before they outgrow thistle-decorated diapers. Here is the story: Long ago the Scots and Norse were at war. One dark night the Norsemen came ashore planning to surprise the sleeping Scottish forces, so removed their boots for a quieter assault. This might have been a fine plan, were it not for the prickly patch of Onopordum acanthium growing between the two armies.

Legend doesn't tell us the exact words which woke the sleeping Scots, however if you grow Scottish Thistle, or if you've ever seen one, you can imagine what kind of cursing might result from a barefoot tread on a small one, much less running smack-dab into a full grown plant in the dead of night. Needless to say, the thistle was credited with saving the day and became the Scottish national flower and emblem.


As ancient Vikings would attest, thistles, even Scottish thistles, are not beloved by everyone. I don't want to sugar coat this. I have seen them grown at such a respectable place as Longwood Gardens, Kennett Square, PA. and written about in such well-regarded references as Tracy DiSabato-Aust's The Well-Tended Perennial Garden. However, in many places on several continents, including this one, they are sometimes considered noxious weeds. Don't tell the Scots. So before I continue, here is a stern warning: If you want to grow them, you must promise, and keep your promise, to not let them become garden juvenile delinquents. Again, in plain language: control them or they will become horrible weeds.

Scottish Thistles are like large breed puppy dogs, Scottish Deerhounds my particular favorite. In the fall a small silver-gray rosette appears and you can't imagine what problems could arise from such a cute little thing. The following spring it begins to grow and grow until soon it's five to eight feet tall and four feet wide and covered with sharp stickers of various sizes. And then it blooms those famous globe-shaped flowers of dark pink and lavender. Much like a Scottish Deerhound grown into maturity, it is a stately, elegant life form, and a lovely shade of grey.

Living Art

I only allow one or two plants to mature each year. Each one grows into a living work of abstract sculpture, a striking specimen plant when placed in the center of a round bed of herbs or perennials or at the back of a boarder. Comments from visitors are guaranteed. Some people are quite intimidated by the size and dangerous looking prickliness of it. However most folks, properly impressed (or so I like to think) by its regal statement, simply ask "What is THAT?" These reactions are surprisingly similar to the reactions you will get when walking in the park with a Deerhound or two. Years ago, when I began growing Scottish thistles (and Scottish Deerhounds), one kind elderly gentleman motioned me aside and sadly told me I had a dreadful weed growing in my garden. I almost felt bad telling him it was the national flower of Scotland but assured him I was careful to make sure it did not spread itself around.

Diligent Deadheading

In order to heed my repeated warning to not allow these Scots to get out of hand, diligent deadheading is an absolute must. This is how I do it. I put on my toughest pair of gloves (even with gloves this plant can stick you) and carefully cut each flower after it finishes blooming. I've learned to catch hold of the flower with the pruners before it drops so I can place it in a waiting container to be thrown out with the trash or burned. If one drops I pick it up with the pruners to avoid a nasty sticker. I keep the container handy so this can be done once or twice a week while the plant blooms through the summer. After blooming is finished in late summer I cut it down bit by bit, using the pruners in the same way to dispose of the entire plant. Then I replace the old plant with a young one to repeat the cycle for another year. Never put one in your compost pile. Seeds may live for up to twenty years in the soil.

Growing Requirements

Scotch Thistles can be grown in zones 5-8. Once established, Scottish thistles will tolerate, even thrive, in poor, dry, gravelly soil and enjoy even the harshest full sun. Studies suggest that seed germination is possible nearly year round, so temperature is not much of a factor, but the alternating daylight and night darkness cycle seems to be necessary. Sometimes seedlings will sprout in early spring, have time enough to grow and flower the first season, however it is classified scientifically as a biennial, not an annual.

Debatable Practical Uses

Onopordum acanthium has another common name, Cotton thistle, derived from the cottony hairs on the stems, which are so numerous that in earlier times it was gathered to stuff pillows. The fat juicy grey disks below the purple florets were once eaten as artichokes, another thistle, are today. Personally I say, "Yuck" to both, but times were tougher and folks had a lot more time on their hands.

Back when Scots were eating thistle dinners and sleeping on thistle pillows, they were also pressing thistle seeds for oil to burn in cooking stoves and lamps. Supposedly it takes twelve pounds of thistle seeds to make three pounds of oil. I have no idea how that compares to growing corn for use in ethanol but I believe Onopordum acanthium would be a lot easier and cheaper to grow than corn. Imagine corn that could be planted year round, germinating in any season or at any temperature and without the use of fertilizers. Sounds like a government grant in the offing. Except for that noxious weed detail.

More History and a Final Warning

Today the highest order of chivalry in Scotland is The Order of the Thistle which legend says was founded in 809 when King Achaius allied with the Emperor Charlemagne. The Order consists of sixteen Knights and Ladies and a few extras, including the British Royal Family. The Order's patron saint is St Andrew and the primary emblem is the thistle. The motto of the Order is "Nemo me impune lacessit" or, for the Latin challenged, "No one provokes me with impunity". Onopordum acanthium everywhere agree.

Read other articles on ecological gardening & native plants

Read other articles by Lee Royer