One of the signs that the end of summer is approaching in my locality is the seeds of willowherb. Willowherb species (Epilobium and Chamerion) have been present in Britain since the Late Glacial Interstadial (13,000 years ago) and began spreading vigorously again at the end of the last Ice Age.
There are eight species of willowherb native to Britain: broad-leaved willowherb (Epilobium montanum), spear-leaved willowherb (Epilobium lanceolatum), pale willowherb (Epilobium roseum), great willowherb (Epilobium hirsutum), hoary willowherb (Epilobium parviflorum), marsh willowherb (Epilobium palustre), square-stalked willowherb (Epilobium tetragonum), and rosebay willowherb (Chamerion angustifolium).
As the Latin names, such as montanum ‘of the mountain’ and palustre ‘of the marsh’ suggest, this ubiquitous plant has evolved to survive in many habitats.
American willowherb (Epilobium ciliatum) was introduced in 1891 and New Zealand willowherb (Epilobium brunnescens) in 1904.
Of these species, three are common in my locality of suburban Penwortham: broad-leaved willowherb, great willowherb and rosebay willowherb.
Broad-leaved willowherb is one of the smaller, most versatile, well-known and well-spread of the willowherbs. Growing from 20 – 60cm, it is typically found on mountains, in woodlands, on walls and on rocks. It grows all over our garden – in cracks in the paving stones, in flower beds; ever the opportunist, it even crashes into the pots of other plants.
Its leaves have short stalks. They are opposite, oval to lanceolate, and are characterised by a broad base. The flowers are on terminal racemes. They are pink, with four notched petals. The stigma has four lobes. They measure 6 – 9mm. The stem is rounded and almost hairless. The seed pods are downy capsules 4 – 8cm long. When the capsules split, they release thousands of tiny seeds, (1mm long and 0.5mm wide) borne on tufts of long, silk white hairs called comas. These act as parachutes carrying them away on the wind to new destinations.
Great willowherb is much larger, growing from 80 – 150cm. It is found on riverbanks, in fens, marshes and damp meadows, preferring neutral soils. Near me, it grows on the edges of ditches and streams in the Meadows, on the edges of the meadow areas in Greencroft Valley and in the meadows themselves. It also scattered around Preston Junction Nature Reserve.
Its leaves are lanceolate and clasping. Its flowers, on terminal racemes, are a deep purple-pink and notched. The stigma, again, has four lobes. They measure 15 – 23mm. The stems are round and downy. The seed pods are 5 – 9cm long.
Rosebay willowherb is the giant of them all. It can grow up to 2m high. It is most often found on wasteland and locally occurs on former and current railway banks. It occurs in abundance at Preston Junction Nature Reserve. It is one of the few native plants that stands its ground to Himalayam Balsam.
Contrastingly, its lanceolate leaves are arranged alternately and spirally on its round, hairless stems. Its flowers, rose-purple, 20 – 30mm, grow in racemes on spikes. Its four-lobed stigmas bend down. Its seed pods are 4 – 10cm and can release as many as 80,000 hair-borne seeds from just one plant!
The wispy white seed-fluff replacing the passionate pinks marks the end of summer. Willowherb, a perennial, will then enter dormancy. Its seed will go on.
Willowherb is versatile and enduring and quite often a pioneer species. Famously, during the Second World War, rosebay willowherb colonised sites of bombings, leading to it becoming known as bombweed or singerweed. It is also known as fireweed because it springs up red in the wake of fires.
With global heating accelerating at a staggering rate and wildfires raging across the world, including here in the UK, it is looking like we will be seeing more of fireweed, more of its seeds, through summer and its end.
“I will go on,” says this plant whose seed bank is now huge, “I will go on.”
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