Thistles are flowering plants characterised by their sharp prickles – some are common weeds but many can be great additions to UK gardens.
Sometimes, the word ‘thistle’ is used to refer only to specific genera – Cirsium, Carduus and Onopordum. However, sometimes it is used more broadly to refer to a wider range of prickly flowering plants. However you define the term, thistles can be very useful and attractive plants for your garden. Even those commonly considered to be weeds can be great choices to consider.
In this article, we will begin by discussing a number of native or naturalised thistles that could be grown in UK gardens. Then we will go on to discuss other plants referred to as thistles or thistle-like plants that you might want to grow in your garden.
Why Grow Thistles in Your Garden?
The first and most important thing to recognise is that some of the plants listed below can be rather thuggish – they can be invasive plants and can quickly become irritating weeds if you do not take care. However, all of the thistles or thistle-like plants on this list are also excellent for wildlife – so it is well worthwhile considering giving them some space in a wildlife-friendly garden.
Thistles of different types are important nectar sources for pollinators. When we are too zealous in getting rid of thistles or are reluctant to give them space in our gardens, we risk diminishing biodiversity and contributing to the loss of many important pollinator species.
The spear thistle ranked in the top ten for nectar production in a survey carried out here in the UK, and this and other thistles are valued by bumblebees, for example, for their high nectar production. Thistles are also important for a range of lepidoptera, and are a favourite nectar source for several native butterflies, including the ‘painted lady’.
Thistle seeds are also an important food source for finches and other seed-eating birds.
You might be surprised to learn that thistles can also be a human food source. A number of thistles and thistle-like plants have edible uses. And can also provide other yields in an abundant and productive garden.
Native/ Naturalised Thistles:
‘Scottish Thistle’ (Onopordum acanthium)
While it is likely to be one of the common plants that springs to mind when you think of the thistle, this national emblem of Scotland, chosen by Sir Walter Scott, is not actually a native plant. It is believed to have been introduced from Europe pre-16th Century and has now naturalised in many areas. Though vigorous and often considered a weed, it can still be a useful plant, in flower from July to September and noted for attracting wildlife. The flower buds can be cooked and eaten, through are a little fiddly, and stems (with rind removed) can be boiled like asparagus or rhubarb.
Spear Thistle (Cirsium vulgare)
The spear thistle, common thistle or bull thistle is the most likely candidate for the true Scottish thistle. This is also abundant in Scotland and native throughout much of the UK. This also has great benefits for wildlife, and has limited culinary uses. The root can be cooked and is somewhat akin to Jerusalem artichoke – and the flower buds can also cooked and eaten. The dried flowers can also be used as a rennet substitute in cheese making. Though it can be a pernicious weed, eating the weeds can be a great way to deal with them while retaining natural biodiversity in your garden.
Melancholy Thistle (Cirsium heterophyllum)
A plant found in upland pastures in the north of the UK, it is common to see it in hay meadows, open woodlands and along streams and woodland verges. It could be another thistle to include in your garden. It takes its name from the idea that it can cure melancholia. Unlike other thistles, it does not have prickles. Its leaves have a dense white felt underneath and it has single purple, thistle-like flowers.
Creeping Thistle (Cirsium arvense)
This is the most common thistle species in the UK and is frequently found on disturbed and cultivated ground. It spreads very quickly and is often considered a weed. But like the other thistles mentioned, it has great benefit to wildlife. Its seeds are an important food source for garden and farmland birds. Like other thistles, these too have historically been viewed as a human food source.
Meadow Thistle (Cirsium dissectum)
The meadow thistle is an herbaceous perennial that is small and slender, without large spines on its leaves. It is a short thistle, up to around 80cm in height, with single pinky-purple flowers. And is commonly found on damp meadows and grassland. It could find a place in a similar habitat in your garden if you are in Southern England, South Wales or Northern Ireland.
Marsh Thistle (Cirsium palustre)
The marsh thistle or European swamp thistle is a tall thistle which produces a lot of nectar for a wide variety of pollinators. It thrives in damp ground such as wet fields, marshes or stream banks. Typically the multiple flowers of this plant are purple though white flowers are sometimes also found.
Woolly Thistle (Cirsium eriophorum)
This is one somewhat more scarce species of thistle that is found mainly in Southern England. It prefers chalk or limestone grasslands and will do well in these conditions in a southern garden. The woolly flower heads of this type of thistle are unmistakable. The reddish-purple flowers top spiny bracts that are covered in ‘white wool’.
Slender Thistle (Carduus tenuiflorus)
The slender thistle, also known as the seaside thistle, occurs naturally occasionally in the UK, mainly in coastal regions. It occurs very infrequently inland. It is quite tall, and bears small pinking flower heads in compact clusters of 3 or more. This is a thistle for coastal gardens with free-draining soil. A similar and more widespread species is Carduus crispus, the welted thistle, which is found in several areas of the UK, south of Edinburgh.
Musk Thistle (Carduus nutans)
The musk thistle is found throughout the UK but is most common in England and Wales. It is a common species of chalky soils and so could be a useful garden plant if you have this soil type where you live. It is common to see this plant on roadside verges or rough grassland, and it could be a good choice for a wilder, less tended part of your garden.
Other ‘Thistles’ and Thistle Like Plants:
Carline Thistle (Carlina spp.)
The Carline thistle produces distinctive brown-and-golden flower heads that resemble a seeded thistle. This spiny biennial plant thrives on dry, chalk grassland in England and Wales. They create interest over a long period, the flower heads look like a thistle that has gone to seed, but they are actually in full flower. And the dead heads then persist, often through winter to the following spring.
Common Knapweed (Centaurea)
Common knapweed is frequently found on all sorts of grasslands around the UK. It has thistle-like purple flower heads and like the true thistles described above, attracts a wide range of wildlife including many native butterfly species including common blues, marbled whites and meadow browns. It can be a great flowering plant to naturalise in your lawn.
Blue Sow Thistle (Cicerbita alpina)
A rare native of Scotland, the blue sow thistle is a perennial hardy to UK zone 4. It thrives in partial or dappled shade and prefers moist soil, and the limited sites where it grows in Scotland are at the edge of its native range. It is a protected species in the UK. If you live in the Highlands then perhaps you could be involved in conservation efforts by cultivating this flowering thistle-like plant. Even in other areas, it can make a good garden plant.
Globe Thistles (Echinops)
Echinops is a genus known commonly as ‘globe thistles’. They have spiny foliage and blue or white flower heads in a spherical shape. Echinops such as the blue globe thistle Echinops bannaticus can be excellent choices for garden plants. They will do best in a well-drained soil in full sun but will tolerate most soils in full sun, or light shade.
Try ‘ Star Frost’, ‘Taplow Blue’, Echinops ritro ‘Vietch’s Blue’ or ‘Arctic Glow’, for example. These are all great pollinator plants and also beautiful ornamental plants for a garden.
Milk Thistle (Silybum marianum)
Milk thistles, also called blessed Mary’s thistles, blessed thistles or lady’s thistles, are robust perennials that form rosettes of large, spiny leaves veined with white, and purple flower heads. Native to the Mediterranean, they can grow in a UK garden in full sun, in poor to medium fertile, well-drained soil that has neutral or mildly alkaline pH. Historically, the plant has been used medicinally to treat liver problems. It also potentially has a number of edible uses, though in nitrogen rich soil can accumulate nitrates, so care should be taken.
Globe Artichoke (Cynara scolymus)
If you were intrigued by the edible possibilities of some of the thistles listed above then you will likely be very interested in growing globe artichokes in your garden. Cynara are thistle-like plants that find a place in many edible gardens. Cynara scolymus is the common edible globe artichoke. The edible portion of the plant is of course the flower bud before the flowers come into bloom. There are a number of edible cultivars that can be grown in the UK. Artichoke hearts are a delicacy common in Italy and other countries, and the leaves covering the choke are also edible.
Cardoon (Cynara cardunculus)
The ancestor of the globe artichoke, the cardoon or ‘wild artichoke’ is another option to consider. The stems of cultivated varieties are also used as food around the Mediterranean, and this is also a source for a rennet substitute used in cheese making. Cardoons can have spiny stems but a number of spineless cultivars have been created to overcome this problem. The leaf stalks look like large celery stems. They can be steamed or braised and have an artichoke like flavour with a little bitterness.
Sea Hollies (Eryngium)
Finally, no discussion of growing thistles in the UK would be complete without some discussion of the group of thistle-like plants called Eryngium. These spiny perennials are dramatic and architectural in form and some look superficially like thistles. They can be great garden plants which can be used to great effect in many garden schemes.
Eryngium, also called sea hollies, will thrive in a very free-draining soil, sometimes even soils that are lacking in nutrients. They do best in full sun. Avoid planting them in rich soils, or in the shade.
Some Eryngium to grow in the UK include:
- Eryngium giganteum
- Eryngium bourgatii
- Eryngium pandanifolium
- Eryngium x tripartitum
- Eryngium x oliverianum
Like the other thistles and thistle like plants mentioned above, Eryngiums not only look beautiful but can also help you to create a wildlife friendly garden.
This list is by no means an exhaustive one. But considering the above should help you find a place for thistles and thistle-like plants in your garden. Whether you want a native thistle, or something to add drama to your garden without getting out of control, you should be able to find the right plants to place in the right positions where you live.