Thistles can be intrusive in the garden. But, their fantastic flowerheads make it all worthwhile 

Monty revisits one of his classic books, Gardening at Longmeadow, in an occasional series. 

All thistles thrive on the heavy soil at Longmeadow, although not all are welcome. The spear thistle, Cirsium vulgare, is a common weed in these parts, developing spines like needles. 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 close cousin the creeping thistle, C. arvense, has a soft, sappy stem which has a habit of snapping off when you try to pull it up. It tends to get in under the hedges of this garden, spreading by lateral roots as well as by seed. 

We also get a lot of sow thistles, which are sappy and easy to pull up in well-cultivated soil and then composted.

The other intrusive thistle here is the burdock. It grows to at least 2m high, and the burrs snag appallingly on any jersey – and the dog’s fur – all winter long. The answer is to cut it at ground level as soon as you see it and to go on doing so until it weakens and dies. 

But it is a statuesque plant and part of folklore – the leaves were used to wrap butter in, and the young shoots and roots used to make dandelion and burdock beer.

There are plenty of thistles that deserve an honoured place in a border. C. rivulare ‘Atropurpureum’ delights in boggy conditions or heavy clay soil and is very happy in our Grass Borders. It grows to about 2.2m tall, has richly plum-coloured flowers, and the leaves are hardly prickly at all. 

It does have a habit of suddenly collapsing and not reappearing the following year. It’s also sterile so will not produce seedlings, so it’s 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. But although its leaves are horribly prickly, the pom-pom blue flowerheads justify the occasional painful brush with them. 

There’s a moment just before the buds open when the heads look spectacularly unplant-like and more like steel tooled to industrial specification. The plant does rapidly make a huge clump, however, so needs rigorous reduction every year or two.

Echinops bannaticus ‘Blue Globe’ has darker-blue flowers, those of E. bannaticus ‘Taplow Blue’ are a more intense blue. E. exaltatus grows to 2.2m with silvery-white flowers.

Perhaps the most popular thistle is the giant sea holly, Eryngium giganteum – actually, it is not really a thistle at all but a distant cousin of the carrot; however, its armoury of spikes and prickles is certainly very thistly.

It is commonly known as Miss Willmott’s ghost because Miss Willmott apparently went round secretly – and irritatingly – scattering its seed in other people’s gardens. 

Nevertheless, it’s a good plant, distinctly silver, tinged with the blue that so marks sea hollies and leaving a dried husk of itself all winter with a seedhead not unlike a teasel, Dipsacus fullonum, which is another incredibly spiky plant and one which loves wet ground.

E. giganteum ‘Silver Ghost’ is smaller and more silvery white. It is a short-lived perennial, which means it’s lucky to flower twice, and like all eryngiums, it prefers well-drained, poor soil.  

HOW TO GROW STRAWBERRIES 

• When strawberry plants stop producing fruit they send out vigorous new growths with foliage spaced out along their length.
• Secure the runner either side of the first set of leaves with bent wire so that the stem touches the soil of a small pot of compost. Cut the runner beyond the pinned section.
• When new growth is apparent – after about 2-3 weeks – cut the runner free from the parent so that it is now a small independent plant.
• Transplant the runners to a new site that has not grown strawberries for three years. They should have a healthy root system and quickly establish as strong plants.