Thistle do nicely! These purple plants will add dramatic beauty to any garden

It can be hard to see a thistle as anything other than a painful weed, and they are all being topped right now by farmers as part of the constant attempt to eradicate them from fields.

The gardener can learn from agriculture in this. If you want to get rid of them, then cutting them just as they flower will do much to weaken them. But do this too early, and they will return with vigour; let them seed, and you are guaranteed more plants than ever next year.

The old rhyme is, 'Cut thistles in May, they'll grow in a day/Cut them in June, that is too soon/Cut them in July, then they will die.'
The common weed in my garden is the spear thistle, Cirsium vulgare, which develops spines like needles and has a characteristic 'Scottish' thistle flower.

Although the farmer may not cut it until July, the gardener wants to get it out long before then, even if it comes back for a second go - when young it can go on the compost heap, but as soon as the spines harden up, it must be burnt or finely shredded.

Its cousin, the creeping thistle, Cirsium arvense, has a soft, sappy stem that tends to snap off when you try to pull it up. It gets in under the hedges of my garden, spreading by lateral roots as well as by seed.

At this time of year we also get a lot of sow thistles - Sonchus asper and Sonchus oleraceus - which are sappy and easy to pull up in well-cultivated soil and then compost.

The dwarf thistle, Cirsium acaule, is the one with an incredibly spiny rosette, which pricks your behind when you sit on the grass.

Wherever they spike you, thistles hurt, and of course it's even more of a pain if you do find your garden filled with them. But if that is the case, you can take comfort in the knowledge that your soil is good, because thistles mostly like a deep, rich loam.

And that is not the only positive note. In fact, rather than denigrating thistles as weeds, my real aim here is to praise their presence. Thistles are beautiful and dramatic, and every garden should have them. The secret, of course, is to choose your thistles with care.

I know there are gardeners who would regard the giant cotton thistle, Onopordum acanthium, as a weed, but I love it and carefully dig up the seedlings wherever they pop up in clusters, and then redistribute them for better effect in our borders.

They are certainly intrusive, growing to at least 10ft and often 15ft, with a spread of 5ft. But they are among the most dramatic garden plants, with huge grey leaves coated with a milky down, fringed with wicked spikes and great candelabras of flowering stems.

The plant needs to be staked in firmly, otherwise it will be brought crashing down in the first summer gale. It is biennial, and the most reliable way to get plants is to dig up unwanted seedlings from a friend's garden.

The best time to do this is in autumn or early spring, before the thistle starts growing again.

When the plant has flowered, it rapidly becomes a spectacular skeleton, which looks fine if supported but makes weeding a nightmare as the spikes become spikier and more painful with age.

Cirsium rivulare 'Atropurpureum' delights in boggy conditions or heavy clay soil. It grows to about 4ft tall, and has plum-coloured flowers and leaves that are hardly prickly at all, which makes it a very borderfriendly plant - although it does have a habit of suddenly collapsing and then not reappearing the following year.

It is also sterile and will not produce seedlings, so it is a good idea to lift it every couple of years and take some root cuttings.

The globe thistle, Echinops ritro, is a tough herbaceous perennial, happiest in poor soil as long as it gets some sun. Although its leaves are very prickly, the mauve pom-pom flower heads justify the odd painful encounter.

The globe thistle rapidly makes a big clump and needs rigorous reduction every year or two. But I love its perfectly round heads, which bear a remarkable resemblance to machine-tooled steel just before the buds open.

Echinops bannaticus 'Blue Globe' has darker blue flowers, while those of E. bannaticus 'Taplow Blue' are a more intense blue. E. exaltatus is huge, growing to 7ft, with silvery-white flowers.

Perhaps the most popular thistle is the giant sea holly, Eryngium giganteum, though it is not really a thistle at all - despite its armoury of spikes and prickles - but a distant cousin of the carrot.

It is commonly known as 'Miss Willmott's Ghost' because Miss Willmott, an Essex gardener of a century ago, apparently went round secretly - and rather irritatingly - scattering its seed in other people's gardens.

It is distinctly silver, though tinged with the blue that so marks sea hollies, and leaves a dried husk of itself all winter with a seed head not unlike a teasel, Dipsacus fullonum, another incredibly spiky plant and one that loves wet ground.

Eryngium giganteum 'Silver Ghost' is smaller and more silvery white. It is a short-lived perennial, which means that it is lucky to flower twice.

All eryngiums like very well-drained, poor soil.

Most thistles are edible - they include artichokes (Cynara scolymus) and cardoons (Cynara cardunculus) - and many have been grown for medicinal purposes.

Cardoons are one of the best of all foliage plants, if you have space for them, as they add great drama to a garden. From February, they start to sprout extravagantly scalloped grey leaves, which grow steadily from large to enormous during summer.

The thistle flowers are carried on huge stalks that are as thick as a wrist and reach 10ft tall in a mature plant.

I leave these all winter or until they topple under their own weight, and the seed heads open out into a wonderful cottony fluffiness right at the end of the year. Their real home is in the vegetable garden. It is a crop that has gone out of fashion, yet the flavoursome blanched stems can taste like a combination of celery, chard stem and artichoke flavours.

Artichokes are very similar to cardoons, but are smaller and more tender, and whereas a cardoon will (weather permitting) happily grow on for decades, artichokes rapidly lose vigour and the ability to produce flowerheads after three or four years.

They are happier with hotter, well-drained conditions, and in my experience the more sun you can let them have, the better they'll grow. Nevertheless, they respond well to plenty of manure and moisture.

The trick is to replace the crop entirely every four years - as one does with strawberries - by ditching a quarter of your plants every year.

Like cardoons, they grow very easily from seed, although side shoots are a more reliable means of producing vigorous, healthy new plants.

For the first year you should cut off any flower heads as soon as they appear, to allow the plant to build up strength. This means having a line of plants in the vegetable garden doing nothing for a year, but it is worth it.

Cutting the first and largest flowering buds provokes the plant into producing more smaller ones, which tend to be tastier, and this is where growing your own crop really comes into play. =

Half a dozen plants will give a plentiful harvest of golf ball-sized artichokes, which can be cooked and eaten simply sliced in half and are truly delicious.

From: http://www.dailymail.co.uk/