Updated: Jun 1
It's thistle time in the garden. Although some can be prickly, others are much friendlier and perfect for damp heavy clay - bumblebees adore them.
I love bumblebees and in my garden, bumblebees love thistles. So much so, that I'm developing a rather strange obsession with all things thistley. The love affair first started though with Cirsium rivulare or the Plume thistle. I have always thought of thistles as large, prickly and often invasive. "Weed" is not a word I like to use (a weed is just a plant in the wrong place) but often they are just that, weeds. They are amazing for wildlife - but their prickles and general bad manners make them too much for the garden.
Thistles are members of the Asteraceae - like the daisy and dandelion, they have hundreds of little flowers packed into each "flower head" - a nectar rich one stop shop.
So, I was surprised to find that Cirsium rivulare has none of these faults. This is a beautiful plant with fabulous magenta flowers. It is tall and upright (about1.5m) with no spines at all. It shoots up each year from a small crown of leaves and, as far as I can tell, neither spreads nor self-seeds. Most surprisingly, it needs moisture retentive soil - it grows like a dream on Cheltenham's wet clay. It flowers in May and June. The flowers are always covered in bumblebees.
Having found this Cirsium, I have hunted out others. Another favourite is Cirsium heterophyllum. This is native to the UK. It's not as tidy as the Plume thistle. With a much bigger sprawl of leaves it's better suited to a larger border or a more naturalistic setting.
It's not quite as tall as the Plume thistle (perhaps 1m) but it is prickle-free and loves damp clay too. It flowers a little later, in June/July and so follows on from the Plume thistle. It doesn't have the vertical height which works so well with other plants but it is still a beauty.
Generally, all of these have purple/pink flowers so it's their height and spread rather than flower colour which will probably determine how you use them in a garden.
Thistles, just like daisies, Asters and dandelions, are composite flowers. They belong to the family Asteraceae - what used to be called Compositae. To us they look like one flower but all of theses plants have flower-heads made up of hundreds of tiny individual flowers. The picture of Onopordum shows these little flowers as they bloom from the outside in.
They give insects access to lots of nectar over a longer period of time than might be the case with a single flower. The flower-head is quite large and flat - making a perfect landing zone for insects too.
You can't go wrong with these lovely plants. If you'd like to get a bit more focused on bumblebees it's useful to know that there are two basic types: some have long tongues and others have short. These types are called "guilds". Not all bumblebees can access all flowers. Some are just too deep for the short-tongued guild. If you'd like to know more about gardening for bumblebees including which flowers long/short tongues can use, there are some great books available.
David Goulson says his book Gardening for Bumblebees is "A practical guide to creating a paradise for pollinators". It tells you everything you need to know to do exactly that. He explains which plants appeal to the two guilds of bumblebees, solitary bees and honeybees too. He also describes how to set up nesting sites for native bees and other pollinators such as hover-flies.
Plants for Bees takes a slightly different tack. It focuses on the plants themselves with good descriptions of a vast range of wild and garden plants. There is a plant Top Ten for honeybees, long-tongued and short-tongued bumblebees, and solitary bees.
Between the two, there is probably everything you'll ever need to make a garden for bees and lots of other pollinators!