Thursday, June 25, 2009

Weeds or Wildflowers?

Every summer Durham University Botanic Garden hosts a wonderful display of annual cornfield weeds (or wild flowers, depending on your point of view). These are species that would have been familiar to Iron Age farmers but have now all but disappeared from the agricultural landscape, thanks to improved methods of cereal seed cleaning and decades of intensive use of systemic herbicides that wipe out weeds soon after germination and never allow them to set seed, so that the bank of seeds in the soil is finally depleted and the species become locally extinct. In Victorian times, when the main method of weed control was manual labour, all these species were serious weeds of crops that drastically reduced crop yields. The cornfield border is the most stunning exhibit in the Botanic Garden at this time of year, eclipsing even the giant Amazonian waterlilies in the glasshouses for their sheer ‘wow’ factor, and is a reminder of what has been lost from the agricultural landscape. Shown here, top to bottom, are corn poppies; corn marigold; cornflower; corn chamomile;corncockle. The whole border positively hums with bees and hoverflies. These are all easy species to grow in a wild flower garden. For more information about Durham University Botanic Garden visit

Tuesday, June 23, 2009

Killer Teasels?

Over a century ago there was considerable debate as to whether the teasel Dipsacus fullonum was a carnivorous plant. It’s not difficult to see why – the bases of the leaves clasp the stem to form a large cup that fills with rainwater and this soon fills with drowned insects. The criteria for a plant being truly carnivorous are that it must lure its prey, trap it, kill it, digest the victim and absorb the nutrients that it releases. Teasel fails on the fourth of these criteria and probably the fifth too – it doesn’t secrete any enzymes of its own to digest the prey and there’s no clear evidence that it absorbs any nutrients from the soup of rotting flies in its drowning pools. But it can certainly lure and trap its prey, in much the same way as a pitcher plant. This bumblebee was presumably attracted by the water in the leaf bases and as soon as it landed it slipped into the water. From that moment on it was doomed. It struggled to climb out but its wet feet slipped on the shiny, smooth surface of the stem and leaf bases. I thought about rescuing it but within less than half a minute it had fallen back in, become totally saturated and had drowned. The teasel leaf bases soon fill with dead insects and must also have a rich population of bacteria and fungi that can digest them, so maybe it’s time for another look at the eating habits of this plant, to check again at whether it derives any nutritional benefits from its decaying captures. Birds certainly do – I’ve sometimes seem blue tits and great tits raiding this gruesome larder.

Monday, June 22, 2009

Here be Giants

This dense forest of great horsetails Equisetum telmateia thrives on the low cliffs and dunes that flank Warkworth beach in Northumberland, but if you could time-travel back to the Carboniferous 300 million years ago, when the coal measures were laid down, you’d see plants that looked very similar. The first amphibians that emerged on land would have slithered between their stems. Today’s horsetails are living fossils – the last few survivors of a group of plants that were once a diverse and dominant component of Earth’s vegetation, thriving in steamy swamps thanks to air channels in their stems that conducted oxygen to their roots and allowed them to survive in stagnant mud. Fossil horsetails from the Carboniferous are common in coal deposits and are virtually indistinguishable from their present-day counterparts – except that those ancient horsetails were true giants of tree proportions, sometimes up to thirty metres tall. Our great horsetail can’t match that – a couple of metres is about the limit of its growth. Horsetails have very distinctive whorls of long , thin leaves at nodes along their grooved, circular stems. They contain large amounts of silica, which gives the dried plant abrasive properties and accounts for its other common name – scouring rush.


There’s an interesting collection of poisonous plants growing in the sand dune system at Warkworth in Northumberland. Of these the most notorious must surely be hemlock Conium maculatum (bottom photograph), which produced the poison that the Greek philosopher Socrates used to commit suicide when he was condemned to death for impiety in 399 BC. The dull red blotches on the stems (second photograph) and a mousey smell are key identification features for this lethal plant, whose main toxic compound is the alkaloid coniine, which is also present in several other poisonous members of the carrot family. The middle photographs are of male (lower) and female (upper) plants of white bryony Bryonia dioica, a deadly poisonous member of the cucumber family that was once cultivated as a medicinal herb. In this species the female plants are particularly conspicuous in autumn, thanks to a crop of glossy scarlet berries that look good enough to eat – which would be a fatal mistake. The top photograph shows the poisonous caterpillar of the cinnabar moth Tyria jacobea, which accumulates toxins from the poisonous ragwort Senecio jacobea that it feeds on. Those warning colours ensure that any bird that attempts to eat it and suffers its unpleasant taste will remember the experience and won’t make the same mistake twice.............except that I have a hunch that cuckoos might be immune. We’ve often seen cuckoos feeding on the ground in the dunes at Warkworth when the cinnabar moth caterpillar season is at its height, and I have a strong suspicion that this is the caterpillar that they’re after. If that is the case, then as far as cuckoos are concerned that orange and black colour scheme must serve as a conspicuous advertisement, rather than a deterrent...

Warkworth Sand Dune Flora

The sand dune system at Warkworth hosts a fine flora in early summer. The top picture shows biting stonecrop Sedum acre, whose succulent leaves allow it to thrive on bare sand in drought conditions. Below this is wild thyme Thymus serpyllum, which releases a wonderful herbal fragrance on hot days and hums with bumblebees visiting it flowers. The next flower down is viper’s bugloss Echium vulgare, whose bristly leaves prevent rabbits from grazing it. This too is a magnet for bees and makes an excellent plant for a bee-friendly wildlife garden. It’s a biennial, producing a rosette of leaves in its first year and a flower spike in the second. The seeds persist for a long time in the soil – I introduced some into my garden about 20 years ago and occasional seeds still germinate, without me ever having sown it again. Behind the dunes at Warkworth there’s a remarkable freshwater swamp, filled with the largest population of yellow flag Iris pseudacorus that I’ve ever seen – it must cover the best part of an acre and just now there are hundreds of plants in full bloom.

Saturday, June 20, 2009

Beachcombing 2

Three more seashells from Warkworth beach – plus something completely different. The top photo shows the familiar pod razor Ensis siliqua. When it’s alive it lives buried in the sand at the low water mark, drawing itself downwards in the sand with an extendable muscular foot and extending two siphons to the surface to circulate water from which it filters food. It constantly moves up and down in the sand, burying itself deeper when threatened, and sand abrasion would create a lot of wear-and-tear on the shell if it wasn’t for that dull brown material on the yellow shell surface. It’s a renewable protein layer called the periostracum, which stops the animal from sanding its own shell away. The periostracum peels away very easily in old, dry shells on the strandline and that’s what has happed to the Iceland cyprina Arctica islandica in the second photo. Freshly dead specimens of this large bivalve, as big as the palm of your hand, are covered with a black periostracum which has worn away in this one. The Iceland cyprina has a very thick shell, so washed up specimens remain intact on the beach for a long time. The third picture shows a thumbnail-sized striped venus Chamelea gallina, which is very common on this beach and lives buried in the sand on the lower shore. You can locate many of these small bivalves by the holes in the sand left by their feeding siphon which are visble when the tide retreats – dig down and you can find the living animal. The last two photographs show the internal shell, or more accurately the 'test', of another animal that lives buried in sand in the intertidal zone and also in deeper water; the sea potato Echinocardium cordatum. This is a sea urchin that lives in a burrow. Those rows of holes mark the locations of the animal’s extendable tube-feet, some of which reach out from the entrance to its burrow to capture food. In life the whole animal is covered in yellowish spines and you can see a few of these still adhering to the test in the lower photograph. The test, made up of fused skeletal plates of the animal, is extremely light and surprisingly strong, surviving the waves to be washed up on the shore, often in large numbers. You can find some photos of the living animal at

Beachcombing 1.

We've just returned from a walk along Warkworth beach in Northumberland with our pockets full of seashells, but sadly they never look quite so good when you bring them home and they dry out, quickly losing the lustre that they had when they were wet. Fortunately I took a few photos of them in situ, as a reminder of their true beauty. Star find was the painted topshell Calliostoma zizyphinum (top two photos), with exquisite colours and a shape that shows how it came by its common name – just like an child’s old-fashioned spinning top. We’ve been walking along this beach for a quarter of a century and in all that time have found less than a dozen of these, so it was nice to see it again. This mollusc feeds in deep water in the sub-tidal zone, so to see the living animal you’d need luck and a very low spring tide - unless you're a diver. The next two photos show two colour forms of the very common but nonetheless delightful banded wedge shell Donax vittatus. This is often one of the commonest bivalve shells on this beach and after storms live specimens, that normally live buried below the sand surface within and below the intertidal zone, are often washed out of the sand. And finally – and this is a tentative identification – a banded venus Clausinella fasciata, about as large as a thumbnail with exquisite purple markings. If anyone can confirm this ID, or knows its certain identity, I’d be grateful for advice.

Thursday, June 18, 2009

Orchids Do It Differently

Most flowers discretely dust their pollen on visiting insects, but orchids go the whole hog and glue their entire stamens to their visitors. The paired stamens – known as pollinia in orchids - sit inside the hooded upper petal (top photograph) and the nectar supply is hidden deep within the flower, so even long-tongued bees like the one in the second photograph must force their head in to reach it. And that’s when they make contact with the base of the pollinia, which become glued to their head, so when the bee leaves it carries the pollinia with it. By the time it’s reached the next plant each pollinium has split open, exposing pollen that’s dusted on to the stigma of the receiving plant. You can see the white, ruptured pollinia just below the antenna on the face of the bee in the third picture, and the same area enlarged on the final image. Bees are often irritated by having these objects glued to their head and sometimes try to comb them off, but seldom succeed. Why do orchids operate in this way? Well each individual orchid flower can produce hundreds – sometimes thousands – of ovules and it needs a comparable number of pollen grains to ensure that they’ll all be fertilised and develop into seeds – despatching a whole stamen’s worth of pollen in one go, glued to an insect, does the trick very nicely.

Monday, June 15, 2009

Ox-eye Daisies

You can’t travel far down a motorway in early summer without noticing drifts of ox-eye daisies Leucanthemum vulgare growing along the embankments, although the threat of being squashed by HGVs mean that you daren’t take your eyes off the road to admire them for more than a second. The daisies seem to dominate every wild flower mix that’s used to re-seed the bare soil after the road builders leave, but I think this magnificent display must have seeded themselves. We came across them at the weekend, growing beside a trunk route from an age when heavy goods vehicles moved at a slower pace - pulled by a horse in a barge - alongside the Chesterfield Canal in Derbyshire. Botanising along canal towpaths is a delightful way to send a summer day...

Saturday, June 13, 2009

Dealing with Duckweed

In summer the surface of our garden pond is covered in a thick layer of duckweed and dealing with it is a real problem. If I skim it off with a rake I inevitably catch a lot of tadpoles and newt-poles that live amongst its tangled, thread-like roots and it takes a long time to release them all and return them to the pond. But this morning I accidentally discovered a quick and simple way to remove duckweed in large quantities, at little risk to the other pond life. I was weeding out sticky Jack (aka cleavers aka goosegrass) and accidentally dropped some in the pond. When I fished it out it was covered with duckweed, entangled in the tiny hooks that cover sticky Jack - see
A handful of sticky Jack did an even better job and after ten minutes of using this technique, which uses one weed to get rid of another, the pond surface was almost clear. I couldn't find any trapped tadpoles in the sticky Jack – the technique just removes the duckweed from the surface. The only problem is that now I’ve run out of sticky Jack – and I know the duckweed will return.

Wednesday, June 10, 2009


The wood pigeons visiting our garden seem to be undergoing something of a population explosion lately. They first bred two summers ago, raising one pair of squabs, and did the same last year. This year they have bred twice already – and it’s only June. I’m rather fond of their soporific coo-cooing on warm summer evenings but what I find particularly interesting is the way they feed their squabs. The parent birds park them in secluded spots in the garden and when they return the excited squab first raises its wings then shuffles up to the parent and puts one wing around its back, as though its hugging a long-lost friend. Then comes the less cute part, where the squab pushes its head down the parent’s throat to induce it to regurgitate food. This ‘hugging’ performance goes on long after the young are well fledged, although as time goes by the parents become less responsive, until the youngsters are forced to fend for themselves. These pictures show the mother-and-child performance on our garden seat this evening.


If you grow dahlias or chrysanthemums for exhibiting in flower shows then this little insect, the earwig Forficula auricularia, is probably your mortal enemy. Earwigs like to rest with their flattened bodies concealed in crevices and the space between closely-packed flower petals is perfect. Unfortunately, while they’re there they tend to nibble the petals. But there is a more endearing side to earwig behaviour; unusually for insects, the females show strong maternal instincts towards their eggs and young. They lay their eggs in late summer and guard them through the winter, constantly licking them to keep them free from fungal infection, and then they feed the infant earwigs through those hazardous first days of life. The earwig in the picture is a male, identifiable by those large, curved tail forceps which are used for defence. When they’re threatened, as this one was, they raise their tails like scorpions, forceps at the ready. Females have straighter, more slender forceps and the other purpose of these organs is for gripping one another, during tail-to-tail mating manoeuvres. Earwigs can fly, but rarely do so. Behind the head there are two sets of wings. The front pair is short and rectangular and probably mainly functions to provide rigidity for the much larger, fan-shaped hind wings. Stowing away the large hind wings is a masterpiece of packaging that involves intricate folding, so maybe it’s not surprising that earwigs rarely take flight. You can find some superb videos of earwigs mating, hatching, defending their eggs and moulting at

Monday, June 8, 2009


Watching this little hymenopteran (can anyone help with the identification?), only about a centimetre long, working its way through the florets of the grasses around my garden pond, provided a chilling insight into this deadly parasite’s hunting technique. Equipped with a long egg-laying tube (ovipositor), it parasitized insect grubs inside the grass florets without ever seeing its prey. The pictures give a clue to how it manages this. It moved from floret to floret, pressing its antennae against each in turn (bottom picture). How did it find them? Was it scent picked up by its antennae tips, or did they detect vibrations from a wriggling, hidden victim? I have no idea, but what is certain is that as soon as it located a hidden host the parasite slid that stiletto-like ovipositor into a floret (top picture), presumably laying an egg in an unfortunate victim whose destiny was to be eaten alive by the hymenopteran's hatching larva.

Monday, June 1, 2009

Crane’sbills: five that are in flower now

Five crane’sbill species are flowering in our wild flower garden at the moment. Herb Robert Geranium robertianum (bottom) seeds itself everywhere and is a great in-filler between other plants. The first of the larger-flowered crane’sbill species to flower is dusky crane’sbill Geranium phaeum, whose rather more sombre but graceful flowers are the first of the larger flowered species to come into bloom. Strictly speaking it’s not a native wild flower, originating from the mountains of central and southern Europe, but it’s quite widely naturalised in the countryside. Next up is wood crane’sbill Geranium sylvaticum, which flowers in hedgerows and woodland edges from mid-spring onwards. It’s followed in early summer by the delightful meadow crane’sbill Geranium pratense, a key component of northern Pennine haymeadows, whose flowers are bluer and leaves more highly dissected than those of wood crane’sbill. Finally, at the top, there’s bloody crane’sbill Geranium sanguineum, a characteristic species of the Northumberland coastline, where it produces fabulous displays in the grassland on the edge of sand dunes. All are united in the genus Geranium by the shape of their fruit, which elongates to resemble a crane’s beak as it ripens; the Latinise generic name for all of them,Geranium, comes from the Greek geranos, a crane.