Bumblebees and poppies: do they see red?

 Human colour vision allows us to see a spectrum of colours that extends from violet to red - the colours of the rainbow - but bumblebees' colour vision is different. They can see ultraviolet, at the short wavelength end of the spectrum, but don't perceive the colour red at the long-wavelength end. But they are constant visitors to scarlet poppies in my garden, so there must be another cue that attracts them from a distance. My guess is that the lure must be a chemical one, a scent that they can detect but we can't, although the contrasting dark whorls of stamens in the centre of the flower would also  be visible to the visitor once they are close enough to see inside the flower. 

I watched this bumblebee make multiple attempts to find its way into the poppies waving in the wind, and once it found its way inside I could hear it buzzing, to shake pollen from the mass of stamens in the centre of the flower. You can see the bluish-grey poppy pollen packed into pollen baskets on its hind legs in these photographs.

Arable weeds

A ripening field of wheat, as harvest time approaches, is an impressive sight - the culmination of 10,000 years of selective plant breeding, aided by the finest agricultural technology that modern science can provide. It's also one of the most hostile environments for native wild flowers.

In winter the soil is ploughed every year and then selective herbicides are used to destroy any wild plant species that manage to germinate. but around the edges of the crop, where the herbicide spray doesn't quite reach, and where there is more light and less competition with the wheat, a select assemblage of annual arable weeds often persists. There presence in arable fields is as old as agriculture itself.

Corn poppy Papaver rhoeas depends on the plough to bring its tiny buried seeds to the surface, exposing them to the light that they need for triggering germination. Most scatter their seeds from their pepper pot seed capsules long before the combine harvester arrives.

Field pansy Viola arvensis is a frequent annual arable seed of crop edges. Its dome-shaped seed capsules split into three boat-shaped segments. They immediately begin to shrink as they dry in the sun, squeezing the seeds - which as smooth and slippery as wet soap - until their are fired out into the surrounding crop.

Most of these arable weeds have small flowers, nonetheless beautiful when you take a close look. This is cut-leaved cranesbill Geranium dissectum. Its tiny flowers are attractive but .....

.... its fruits are exquisite too. Here they are, ripe and ready to go - five seeds each in their own capsule, attracted to a strip of tissue that runs right to the tip of that beak-shaped structure. It becomes as tense as a clock spring as it dries, until the capsules break free and are flicked upwards, hurling out their seeds like a medieval siege catapult.

After the seeds have been discharged the fruits remain attached to the plant, like miniature chandeliers.

Most of these small arable weeds have no impact on crop yield, but sometimes more serious agricultural weeds survive and can become a problem - this is wild oat Avena fatua, whose seeds have a remarkable ability to drill themselves into the soil, which you can see by visiting this post.

The Itinerant Flora of a City

Every year the cityscape of Newcastle changes, as old buildings are demolished and the legacy of polluting industries from the past is cleared away. This site is in the Lower Ouseburn valley, once the location of a devil's caudron of industrial pollution but soon to become the site of 76 energy efficient 'green' homes. 

The patch of land in this picture has been derelict for several years - just a pile of broken bricks and earth bulldozed and then left, so that temporary colonisers took over.

Two years after the land was bulldozed, in the summer of 2011, it hosted the finest display of dyers rocket aka weld Reseda luteola that I've ever seen.

The site was so densely covered with this bee-friendly biennial that I wondered whether it might be the legacy of these plants being used in dye production in the 19th. century; in his New Naturalist book Weeds and Aliens Sir Edward Salisbury suggests that the plant's abundance and distribution often suggests that large populations are relicts of the plants' former cultivation. They have a vast seed output (Salisbury quotes up to 76,000 seeds per plant) and it's possible that the seed could have remained dormant for many decades.

There was also a good display of corn poppies amongst this temporary urban field of wild flowers. Their seeds germinate in even the smallest area of waste ground in Newcastle when they are brought to the surface by soil disturbance and exposed to light and moisture. 

Now that the site has been levelled and the rubble taken away, these plants will be on the move again - carried as seeds in rock, bricks and soil that have been taken away and probably used at another site in another part of Newcastle - part of the itinerant flora of the city.

Three-headed Monster

We found this three-headed corn poppy in Teesdale this morning. Sometimes abnormalities like this can be caused by herbicide sprays but, since there were other perfectly normal flower stems on the same plant, I think this was simply a chance developmental aberration. The flower stem is flattened like a plank - fasciated in botanical parlance - and this sometimes happens when growing points that would normally develop into separate shoots become joined together. There can be a variety of causes, including physical damage by an insect or pathogen, infection by the bacterium Rhodococcus (Corynebacterium) fascians, environmental shock or a genetic cause. There are other examples of fasciation here and here.

Here's a normal one...

Remembrance

Poppy seeds need light to germinate, so every time the soil is cultivated buried seeds that are brought to the surface germinate and produce a blaze of scarlet flowers. Every year for the last 25 years, since we moved into our house, unsown corn poppies have flowered in the vegetable garden. This year's crop has now set seed, leaving these elegant little pepperpot-like seed capules - delightful objects of natural sculpture - that are the last reminder of the vivid splashes of flowers that graced the potato patch back in July. They've shaken their seeds out of the pores around the rim and added to the seemingly inexhausible seed bank in the soil.

Earlier this week I came across a remarkable account of the mass- flowering of poppies, in an obscure journal called the Bulletin of Miscellaneous Information, published by the Royal Botanic Gardens Kew in 1917. The article is called The Flora of the Somme Battlefield, written by someone who simply signed themselves with the initials A.W.H. It's an account of a visit to the battlefield in the summer that followed the great battle of summer and autumn 1916. It must surely be one of the most poignant botanical accounts ever written, and I can do no better than to quote the author's own words.

Image: The effect of artillery bombardment - Passchendaele village, before and after the battle of 1917. http://en.wikipedia.org/wiki/Battle_of_Passchendaele

"Villages, roads, open country, and woodland have been destroyed and ploughed up again and again by shells, with the result that hardly a level spot can be found. The surface of the ground is everywhere more-or-less pitted with shell-holes of varying size and depth, and can best be imitated by arranging innumerable cups and basins as closely together as possible so that their rims shall reach a general level. It is only on the rims of the shell holes that walking is possible".

"Looking over the devastated country from the Bapaume Road one saw only a vast expanse of weeds of cultivation which so completely covered the ground and dominated the landscape that all appeared to be a level surface. In July poppies predominated, and the sheet of colour as far as the eye could see was superb; a blaze of scarlet unbroken by tree or hedgerow".

"Charlock occurred in broad patches ....... though masked by the taller poppies. Numerous small patches were, however, conspicuous and these usually marked the more recently dug graves of men buried where they had fallen. No more moving sight can be imagined than this great expanse of open country gorgeous in its display of colour, dotted over with half-hidden white crosses of the dead. In no British cemetery, large or small, however beautiful of impressive it may be, can the same sentiments be evoked or feelings so deeply stirred. Nowhere, I imagine, can the magnitude of the struggle be better appreciated than in this peaceful, poppy-covered battlefield hallowed by its many scattered crossses."

A.W.H (1917) The Flora of the Somme Battlefield. Bulletin of Miscellaneous Information, Royal Botanic Garden , Kew Nos. 9 & 10, 1917, pp. 297-300.