Eupatorium: a eulogy

The fashion for prairie planting, or the New Perennial style as some designers prefer to call it, may not be universally popular with gardeners, but it’s very good news for the honey bee.

Prairie planting is all about letting plants do what comes naturally. You don’t have to stake them, or prune them, or deadhead them. You choose things like asters, or rudbeckia, or echinacea, that will establish massive colourful clumps that sway in the breeze without collapsing in a heap every time it rains. Most prairie planting schemes incorporate lots of tall grasses, such as miscanthus, or pennisetum, or panicum, and even as autumn turns into winter, their bleached flowerheads still add movement and texture.

Eupatorium combines beautifully with late summer/autumn perennials such as asters and solidago, as seen heret in the herbaceous border at Waaterperry, near Oxford.

So what’s not to like? Well, some gardeners don’t like grasses - they think they look scruffy,  or weedy, and will run riot in the borders. I’ve never understood the anti-grasses thing, because I’m a lazy gardener and evergreen grasses such as carex, stipa and acorus form a year-round framework that saves me having to think of anything else to put in their place for half the year. They look just as good with tulips and daffodils in spring as they do with Michaelmas daisies in late summer and autumn.

To be fair, not everybody’s garden is suitable for a prairie planting scheme, because this sort of planting work best where everything gets its fair share of light - in an island bed, say - rather than in conventional borders around the boundaries. However, you don’t have to have acres and acres of space or, indeed, a prairie. One very good example is the High Line in New York, the converted overhead railway line designed by Dutch plantsman and prairie pioneer Piet Oudolf.

The plants themselves tend to be on the big side - a metre-plus in height on average, if not more - and one of the most impressive is Eupatorium maculatum, known as Joe Pye weed in America, where it is a food source for Monarch butterflies on their long autumn migration south to Mexico.

In this country, you will see Eupatorium maculatum ‘Atropurpureum Group’ and Eupatorium purpureum listed in nurseries and catalogues. You may also see the name Eutrochium maculatum, because the botanists have just reclassified this plant, and in their usual fashion have come up with something that is even more difficult to pronounce. “Eutrochium” sounds more like someone clearing their throat than the name of a plant.

Matthew Wilson, a regular on the Gardeners’ Question Time panel, is a fan of Eupatorium purpureum because it is a good plant for blurring the boundaries between garden and surrounding countryside. Whatever the name, however, most eupatoriums look vaguely alike - dark green leaves arranged in a star shape around dark red stems, topped with domed clusters of pinky-lilac flowers. 

And they are all big. They form a clump of up to two metres in width and height, so definitely a choice for the back of the border, or at least somewhere they have room to spread out. Some varieties are more compact: ‘Gateway’, for example, which is stocked by Knoll Gardens, the grasses specialist in Dorset. However, “compact” is a relative term in this case - even ‘Gateway’ can grow to six feet, and the “dwarf” varieties such as ‘Little Joe’ and ‘Baby Joe’ will form clumps a metre high.

Despite this, they are not overbearing, in-your-face plants. Although they form big clumps, the subtle colours of the flowers produce a smoky, misty purple effect that recedes rather than intrudes.

So who was Joe Pye and why is eupatorium called Joe Pye weed? There are almost as many legends about the name as there are species and cultivars of eupatorium, but the generally accepted story seems to be that Joe Pye was a Native American, who used eupatorium as a remedy for typhus. Other stories say that Joe Pye is a corruption of jopi, or jopai, a Native American Indian name for typhus.

Whoever or whatever Joe Pye was, eupatorium was also used as a cure for gallstones or kidney stones (hence another of its common names, gravel root), and rheumatism. Traditionally the plants were dried, and put into to hot water to make a kind of bitter tea. Herbalists often added cayenne or ginger, and honey to make the drink more palatable. It is tempting to wonder whether it was the hot water or the ginger or cayenne that was really responsible for making you sweat, but eupatorium is still used by homeopaths as a remedy for fever.