Wednesday, January 9, 2013

Winter Sun

Who needs to fly to exotic places when winter sun can be found just down the road? Yes, walking a few hundred yards down to the beach is much more sustainable. A bargain beach getaway for the well insulated traveller.

On the shingle, near Walmer Castle, winter heliotrope (Petasites fragrans) is in flower.

Winter heliotrope was introduced, as an ornamental from the Mediterranean and North Africa, in 1806, and is now naturalised in lowland Britain, being first recorded in the wild (in Middlesex) in 1835. It's not really frost tolerant but does survive our winter and flower successfully where it finds some frost-protection (so you don't find it so often in Northern Britain). Odd that a native from the Mediterranean is one of our few early nectar sources for insects.

The patches on Walmer beach are flowering quite prolifically this year. The densely hairy flowering stems are about 10 inches tall. The leaves are large and heart-shaped.

Petasites is from the Greek petasos, a broad-brimmed hat worn by shepherds. Fragrans of course means fragrant. The flowers have a delightful vanilla scent.

Buds have scaly bracts...

...protecting the delicate florets.

As the flower opens it develops a purple tinge. Winter heliotrope is not a true heliotrope (Heliotropium). It just looks a bit like it. 

Heliotropium arborescens in Vancouver, Stan Shebs, 2005, Wikipedia
Used under a CC BY-SA 3.0 license. 

Or not. 'Heliotrope' is also used to describe something tinted pink-purple

True heliotropes are in the borage family, winter heliotropes in the daisy family. True heliotropes were so named because their flowers tracked the sun; Greek helios (ηλιος) means 'sun' and tropos (τροπος) means 'turn'. I'm unsure if winter heliotropes track the sun. It was too cold to stand and watch. Although winter heliotrope and true heliotrope aren't related they both contain pyrrolizidine alkaloids which are liver toxic if ingested. 

Looking more closely at the flowers, the outer florets are asymmetrical and serve to attract pollinators.

The central florets are pentaradially symmetrical like small purple-tinged stars. The white sticky-out bit is the pollen. Winter heliotrope is dioecious; it has separate male and female flowers. Only male flowers have been seen in the UK, so the vanilla scent and pretty flowers are for nothing. The plants reproduce vegetatively.

It is known amongst gardeners as a somewhat alarmingly spreading plant. The foliage forms a dense shady blanket, probably great for small mammals, not for native flora. It has extensive rhizomes so is patch-forming, blanketing the ground and excluding other plants. It's difficult to remove by hand because any fragments accidentally left in the soil can regenerate.

Oddly, the otherwise excellent Kingsdown & Walmer Beach Management Plan makes no mention of this invasive plant, even though there are some pretty large stands.

Winter heliotrope is very similar to butterbur (Petasites hybridus), to which it is closely related. Key differences are, the winter heliotrope's earlier flowering time and less dense flower heads.

Butterbur (Petasites hybridus)

Whilst researching for this blog I came across this Guidelines on The Management of Noxious 
Weeds and Non-Native Invasive Plant Species on National Roads (2010) from the Irish National Roads Authority. Winter heliotrope is on page 52.
DEFRA Non-native species factsheet Winter Heliotrope Petasites fragrans