Willow flowers (or Vegetable Goslings)

Willows (Salix genus) are one of the earliest flowering tree species in the UK and are a fantastic nectar source for early pollinators such as bumblebees and butterflies. These trees are dioecious which means that there are separate male and female trees which can be distinguished by their flowers. Another more commonly known example of a dioecious tree would be the holly – only the female trees bear the red berries. One of the traditional names for willow flowers was ‘vegetable goslings’ which seems a perfect description to me!

Male willow flowers
Male willow flowers – the bright yellow pollen is on the end of the stamens and this brushes onto the pollinators when the come to drink from the nectar.

The flowers are quite unusual when compared with a simple flower such as a buttercup which follows the classic textbook diagram. Willow flowers are catkins – these are spikes of numerous tiny flowers rather than each catkin representing a single flower. Each of the yellow-tipped spikes in the male flower is one of the stamens and there are generally two or more of these to each individual flower within the catkin – the number varies with species. The same is true, although less easily illustrated, for the female flowers which have two or more stigmas per flower.

Female willow flowers
Female willow flowers – these are much less showy and do not have the yellow pollen of the male flowers. They also provide nectar to attract pollinators with the hope that the previous flower visited will be a male willow of the same species and thus the pollen will be transferred and the female flower fertilised.

The male and female flowers appear at the same time in order that the pollen from the male flowers is able to fertilise the female flowers. The flowers are quite different from one another in appearance and, side by side, it would be easy to assume that a male and a female willow tree were two different species.

Development of male willow flowers
Development of male willow flowers. On the left you can see the red outer scale to the bud which breaks and the catkin emerges from beneath. The first flowers on the catkin begin to open – the red tipped stamens can be seen. The yellow pollen then begins to be produced and finally the bumblebee comes to drink from the nectar and incidentally collect the pollen whilst doing so. This is an early bumblebee (Bombus pratorum) and the willow species is Salix x laestadiana which is a hybrid of goat willow and downy willow.

The willow flowers are an excellent source of nectar for early pollinating species, such as queen bumblebees which have emerged from hibernation and are establishing nests, or the early Nymphalidae butterflies which hibernate through the winter.

Small tortoiseshell butterfly on female willow flower
Small tortoiseshell (Aglaise urticae) butterfly on female willow flower. Note the presence of the nectar source in the centre of the catkin whilst the yellow-tipped stigma is higher. The stigma is where the pollen must reach in order to fertilise the female flower and this design encourages successful pollination which is an incidental rather than intentional act on the part of the pollinator which is only interested in a free feed!
Unidentified solitary wasp on female willow flower
Unidentified solitary wasp on female willow flower – any ID tips would be most welcome! This demonstrates the effectiveness of the design of the female flower – see how the wasp must bend low into the flower to reach the nectar source, so bringing its body (which will hopefully be dusted with pollen from a male flower) into contact with the female stigma.

Brimstone butterflies – the perfect harbinger of spring

Brimstone butterflies are the perfect harbinger of spring. They are typically the first butterfly seen in most years – excepting the occasional tatty small tortoiseshell or peacocks – and they always look pristine. Perhaps the connection with spring is so strong because they confirm our own perception of the first spring day – they need the warmth and clemency of sun and still blue-skies in February or March to take to the wing.

Brimstone  (Gonepteryx rhamni)
Brimstone (Gonepteryx rhamni)

I saw my first brimstone of 2014 a couple of week ago but they were out in abundance last Sunday – settling on the south-facing hedge in the garden to warm up and bask in the sunshine. A short drive across the Vale of Belvoir saw almost every hedge graced with at least one which bobbed and bounced around the periphery of the foliage.

The brimstone is one of five or six species of butterfly which hibernate in the UK. You may see much tattier and battered small tortoiseshell, comma and peacock butterflies at this time of year along with the occasional clouded yellow and, increasingly, the red admiral. All of these, excepting the brimstone and the clouded yellow, are in the Nymphalidae family – a group which includes many other familiar UK butterflies including the fritillaries and the browns. The brimstone is in the Pieridae family which also includes the whites.

Hibernating peacock butterflies which find dark places such as sheds, roof spaces, tunnels and tree cavities to close up their wings and wait for spring to return.
Hibernating peacock butterflies which find dark places such as sheds, roof spaces, tunnels and tree cavities to close up their wings and wait for spring to return.

Brimstone butterflies are a single brood species – the adult butterflies emerge in August and are on the wing, feeding and building up fat reserves, until they go into hibernation at the end of autumn. The butterflies, also called imago, re-emerge early in the spring to mate and begin their life cycle once more.

The comma and small tortoiseshell butterflies, in the Nymphalidae family, tend to have two broods in a year – that is the first batch of imago will mate and lay eggs which hatch and give rise to a second batch of imago in the same year. The red admiral has a single brood but the prevalence of imago is affected by migrating butterflies from the continent. The peacock has rather a similar life cycle to the brimstone.

It is always noticeable that the brimstone butterflies look pristine in spring, whereas the commas and small tortoiseshells often look much more battered and tatty. I was hoping this might be explained simply by the Nymphalidae butterflies being older – that is they had been on the wing longer in the previous season before hibernation, but the phenology doesn’t seem to bear this out for all. It could explain the particularly tatty comma and small tortoiseshell butterflies, if some of these are surviving stragglers from the first brood of the previous year.

Comma butterfly (Polygonia c-album)
Comma butterfly (Polygonia c-album)

 There is still a difference in family between the brimstone and all of the other hibernating butterflies and I wonder whether the brimstone is simply a more structurally sound butterfly, with stronger wings which are less likely to deteriorate than the other species. The species is the longest living of the UK species, at a year, so the imago would need to be hard-wearing! I would be fascinated to know an answer to this if anybody can advise.

Small tortoiseshell (Aglais urticae)
Small tortoiseshell (Aglais urticae)

The brimstone butterflies feed on a range of nectar sources – as they are so early to emerge they rely initially upon long-flowering species such as dandelion, or early flowering species such as bluebell, cowslip and primrose. The key food plant in the autumn is thistles with a range of other species also used.

The larval food plant is surprisingly specific and not abundantly common – they require buckthorn or alder buckthorn. The species name for the butterfly eludes to this link – rhamni which refers to the latin for buckthorn – Rhamnus sp. This is a shrub which can be found in hedgerows and woodlands but is not nearly as common as other similar species such as hawthorn or blackthorn. I do not know of any buckthorn in the area but the presence of the brimstone butterflies clearly proves its existence! The comparative scarcity of buckthorn has been directly addressed by Butterfly Conservation in the past with planting programmes to increase their presence within landscapes and this has had a positive effect on the brimstone populations.

The female is much paler than the male – I saw one in the distance on Sunday which I at first through to be a large white until I crept closer and saw the distinctive veined, contoured folded wing which looks so much like a leaf.

Brimstone  (Gonepteryx rhamni) pretending to be a leaf

Tree bumblebees in Grantham

Bumblebees are fascinating insects and I have been meaning to learn more about them for a long time. I’m not sure that it doesn’t have something to do with the fact that they looks quite so similar to colourful bats up close… there is something about their furry round bodies which is rather reminiscent!

It is still very early in the season but most of our UK species respond to conditions rather than dates and when the sun is shining and the weather is mild, many hibernating species will come out of torpor and begin their spring routines. I have recorded pipistrelle bats in flight over the last week; the birds are certainly thinking about nesting with the early species such as long-tailed tits gathering nesting materials; and there was quite a gathering of bees on a very early flowering blackthorn on Monday lunchtime.

I managed to get a couple of photographs of this bumblebee and decided that this would be the first ID on my path to learning more about these species. And it looks as though I picked quite a good one – my tentative ID of a tree bumblebee (Bombus hypnorum) was confirmed by helpful tweeters @sbd08simon and @ed_p_wildlife. Apparently there is no other bee which this species can easily be confused with – the colouration is just black and buff-brown with a white tail. No coloured bands! This bee has quite a simple pattern compared with the multitude of variations which other species seem to manage! This guide from Bumblebee Conservation gives a great introduction to identifying bumblebees.

Tree bumblebee Bombus hypnorumAlthough I am, as already confessed, no expert, I believe this must be a queen out foraging and potentially searching for a nesting site. The queens emerge in spring (usually March or April) and scope out potential nesting sites before laying their eggs. About six weeks later, the eggs hatch and the entirely female workforce splits into teams, some foraging for the colony, others staying in the nest to do the housework. Later in the year, ‘reproductives’ are produced – these are virgin queens and/or drones. The drones will die after mating with a female but the queens will hibernate through the winter and emerge when the temperatures warm up in the spring and the cycle can begin again. I would therefore suppose that my bumblebee feeding in February is a queen freshly emerged from a relatively short winter’s sleep.

Tree bumblebees are so called because of their habit of nesting in trees – either in woodpecker holes or more frequently, in nest boxes. Like most species, they have adapted to inhabit the world we have created around them and can also be found nesting in houses, in soffit boxes and similar features. Some other species of bumblebee will occupy similar niches but the preference for these tree (or tree-like) nesting sites is most notable in the tree bumblebee. Many other UK species will nest underground and you can often see them bumbling into the undergrowth towards the entrances to their underground homes.

Tree bumblebees are a relatively new additional to the UK’s fauna – they first appeared in Wiltshire in 2001 and have been spreading north every since. It is believed that they are natural colonisers which have established under their own steam, much like the collared dove which was a rare vagrant until the 1950’s when they were first recorded breeding here and now grace most garden bird tables across the UK. The invasion of the tree bumblebee appears, so far, to be benign with no observed impacts upon existing native bee populations and its spread appears to be continuing with the first recording in Scotland last year.

I have recorded my sighting here – the data gathered from recordings around the country can be used to study this species and describe its distribution around the country.

If you want to read more about the tree bumblebee, there is a very informative factsheet available from Bumblebee Conservation.

Tree bumblebee Bombus hypnorum on Blackthorn Prunus spinosa

Spring flowers

Spring flowers are beginning to appear everywhere! The weather has turned colder now again but spring is still certainly on the way – here are just a few of the species to be seen around Grantham at the moment, there will be many more to come!


Blackthorn (Prunus spinosa)
This is a typical component of hedgerows throughout the country and there are plenty of examples of it aroung Grantham. Most of them are not yet in flower but this specimen growing on its own beside the river seems to be at the head of the pack! Start looking out for the white patches in the hedgerows around now – blackthorn comes into flower before its leaves unfurl which makes for a beautiful spring sight with a mass of creamy white blooms.

You may know blackthorn as sloe – the small purple plum-like fruits which can be used to make sloe gin, jam and, well, little else. These are generally harvested after the first frost of autumn so it will be a long time before these flowers produce ripe fruits.

Blackthorn (Prunus spinosa)


Flowering cherry (Prunus spp.)
This is another non-native but very welcome spring flower. There are two native species of cherry tree – wild and bird – but the majority of those you are likely to see around are ornamental varieties. This one is growing on Sandon Road, outside of the construction college but you can see them flowering in gardens and public spaced throughout Grantham, including the town centre.

You might notice how similar the cherry and the blackthorn flowers are – they are in fact in the same genus, the prunus. This genus includes all of the cherries including familiar fruits – cherry of course, apricot, peach and plum, as well as almonds which are effectively the stone you might be familiar with and not, therefore, a true nut.

Cherry blossom viewing is one of the highlights of the year in Japan – they have blossom viewing parties and events and there are even forcasts which predict when the blossom will be in its fullest glory around the country, depending upon geographic location and weather conditions. I’m not aware that this has caught on to the same extant here in Grantham, but the flurry of whites and pinks certainly do cheer up the town as you walk through.

Cherry (Prunus spp.) blossom


Snowdrop (Galanthus nivalis)
One of the most widely recognised spring flowers, these are generally considered to be a naturalised rather than a native species. They are found as natives across Europe and certainly fend for themselves in this country but the first recorded colonies were in the 1770’s *. It is possible that some plants are native however, especially in the south of England, however these on the bank of Grantham College are almost certainly planted. One of the earliest spring flowers, they are probably coming to an end now as the weather begins to warm.

You do get many cultivars and ornamental varieties too – if you want to see a nice display, Easton Walled Gardens, just along the A1 south of Grantham, has a snowdrop week once a year, however you’ll have to wait until next year for the next one!

Snowdrop (Galanthus nivalis)


Lesser celendine (Ranunculus ficaria)
This is a small native species in the same family as the buttercup – the Ranunculus family. The small yellow flowers are another characteristic of early spring and grow in abundance due to their habit of spreading by rhizomes as well as seed. They are most apparent on warm sunny days such as this as they are only open during daylight and close up when it is dark or overcast.

They can be found in many places – they are often present in woodlands or along the bases of hedges where they can spread out into adjacent grasslands. They bloom early in the year, preceding the trees coming into leaf – when they grow beneath a wooded canopy, spring is the time when they will get the maximum amount of light. The plant will die back in May and then remain dormant for much of the remainder of the year.

These flowers were growing alongside the snowdrops on the bank of the college on Stonebridge Road.

Lesser celendine (Ranunculus ficaria)

As an extra bonus, which I didn’t even notice until uploading this picture, is a tiny little ivy-leaved speedwell (Veronica hederifolia) growing within the celendine patch – see closeup below! You can see where it derives its name from too and, in this case, the latin is a very good reflection of the English. Ivy-leaved speedwell (Veronica hederifolia)Hedera is the ivy family and folia derives from the latin for leaf; hence ivy-leaved. Veronica is the family name of the speedwells.. This species generally flowers in April – May but it must have found particuarly favourable conditions settled in amongst the celendines.