Rusty groundsel

 To many gardeners it's a weed; to botanists it's a wild flower; to ecologists it's a ruderal - a primary coloniser of disturbed ground. Call it what you will, groundsel Senecio vulgaris is a remarkable plant. It flowers all-year-round, produces seeds by self-pollination without the aid of pollinators and can thrive in an extraordinary range of habitats. 

Tenacious two-inch-tall plants can grow in a crack in the pavement and produce a single flower. Bushy, lush plants growing in a nutrient-rich farmyard can produce hundreds of flowers and thousands of seeds, which are carried away on the wind but are also eaten by finches, though the seeds can also pass unharmed through a bird's gut and germinate successfully. The seeds also have a covering of microscopically small hairs that extend when wet and help the seed to stick to animals' feet. 

The generation time of a groundsel plant is often around three months, so in a single year,  in favourable conditions, a single seedling can give rise to a million descendants. 

A wild flower for all seasons, then, and a plant on a world tour, taken to North America and Australia by European migrants long ago.

 

The name groundsel comes from the Old English word grundeswilage, meaning ground swallower. I always imagined that the generic name, Senecio, derived from the Latin senex, meaning 'old man' referred to the greyish-white whiskery plumes of its airborne seeds, but the real explanation can be traced back to botanist William Turner in 1538, who wrote that 'when the wynde bloweth it away, then it appeareth like a bald headded man, therefore it is called Senecio' ..... and in the photo below you can see what he meant.

Groundsel has an Achilles heel, a rust fungus called Puccinia lagenophorae, which has an interesting history. It is an Australian fungus, that infected groundsel there and was imported into the UK on groundsel that accidentally made the return journey to the UK, most likely with imported horticultural plants, and was first noted here in 1961. It has since spread throughout Britain and somehow crossed the Atlantic, first being observed on groundsel plants there in 2001.

Groundsel rust, being an efficient parasite, doesn't kill its host outright but does weaken it and render it susceptible to other fungal pathogens, like mildews.

The spore cups of Puccinia lagenophorae are quite beautiful when you look at them like this, magnified under a low-power microscope, appearing like tiny sunbursts with sunbeams formed from radiating chains of spores.