Friday, August 10, 2007

The Butterfly Bush Buddleja davidii

I am an amateur naturalist trying to learn a little about all the life in my garden.

Growing in my garden (at (1.5,0.5) -see here) is a Butterfly Bush (Buddleja davidii). You can see the bush itself in photo 2 (click to enlarge) and a closeup of one of the beautiful flower 'spikes' (my description - the professionals appear to favour the catchy 'a paniculate cyme') in photo 1. The flowers smell as wonderful as they look.

You can find numerous buddleja cultivars in garden centres. The Royal Horticultural Society site has a picture of seventeen of them. As far as I'm aware mine is not an artificial cultivar (can anyone confirm this from the photo?). Paignton Zoo holds the UK's national collection.

The buddleja in my garden grows vigorously and I regularly need to prune it back. True to its common name, it is a magnet for butterflies and other insects - an example being the peacock butterflies I photographed recently feeding there.

Amongst the many pleasant consequences of my self imposed mission to blog my garden is the discovery of so many excellent web resources. In preparing for this posting for example, I came across the excellent UK Biological Records Centre, a database of 15million entries on 12,000 UK species. Amongst the resources, the centre offers a downloadable database providing information on all the alien species of plant and animal to have invaded the British Isles. From the database I learn that Buddleja davidii was first grown in the UK at the famous the Kew Gardens in 1896, and it was not until 1922 that the first wild 'escapee' was recorded (at Harlech in Wales - how seed travelled the several hundred miles from Kew to Harlech I can only imagine!). The latter date surprised me - if I'd been asked to guess, I think I'd have imagined buddleja to have been imported by some intrepid seventeenth century plant hunter. These days you'll see Buddleja davidii on almost any patch of rough, stony ground in the UK and I've been told that it was extremely common on bomb-sites at the end of the second world war; To have spread so widely since only the 1920's is a testament to its hardiness (mine has survived having being ripped out of the ground by the bulldozers of the builders who did some work on my house a few years ago for example!).

The species name daviddii refers to one Father Armand David, a French Catholic missionary and keen naturalist. The first Westerner to discover it, Father David found Buddleja davidii growing on gravel river beds in China in 1876 (or 1869, depending on which web site I look at - does anyone know which is correct?). Father Armand had a prodigious talent for discovering plants and animals: over a thousand new species (including the giant panda - none of those in my garden as far as I'm aware!).

The genus name Buddleja is a reference to the Reverend Adam Buddle (1662-1715) an Essex botanist whose collection of moss, grasses, seaweeds and lichens is today housed in London's Natural History Museum. Mark Lawley's site includes a biographical essay. The name Buddleja was coined by Linneaus in honour of the Rev. B - the Reverend himself never actually encountered the plant. 'Buddleja' is Linneaus's spelling, although it's common to see the alternative 'Buddleia'.

The Buddleja genus contains some 100 species, widely spread across the globe. Buddleja davidii is classed as a problem weed in the US.

And finally, a little microscopy? But of course! For no more reason than its intrinsic fascination value, some buddleja pollen (photo 3, 400x magnification, click to enlarge).

Sunday, August 5, 2007

Common Field Grasshopper (Chorthippus brunneus)

I am an amateur trying to learn something about everything living in my garden.

Sunning itself on (appropriately enough !), my garden sunlounger I found the grasshopper seen in photo 1 (click to enlarge).

I am used to hearing the chirp of grasshoppers on warm days when I go for country walks hereabouts. I do not tend to hear them in my garden however. The grasshopper in the photo is one of only two I can recall having seen there.

Prior to this posting I knew essentially nothing about grasshoppers. Thanks to reading the short but scholarly Grasshoppers and Bush-crickets (Andrew Mahon, publ. Shire Natural History) however, I am now a little better informed.

For the amateur, learning to identify all the British grasshoppers is a realistic proposition (arguably unlike mastering the beetles !) as there are only eleven species, together with ten species of bush cricket. (Amateurs from 'the rest of the world' be warned however, elsewhere a further eleven thousand species are there to be encountered!).

Bush-crickets can be distinguished from grasshoppers, in part, by their longer antennae (typically, longer than their bodies).

Grasshoppers are vegetarians (some bush-crickets are carnivorous). They overwinter as eggs, typically laid into soil or at the base of vegetation, and, following hatching and a period spent as a grub-like larva, grow to adult-hood through a series of nymph-stages (instars), moulting their exo-skeleton between each stage.
Using the key in the book above and working from my photographs, I was able to make some progress towards identifying my grasshopper. Based on my grasshopper not having antennae swollen at the ends into clubs, I understand that he (or she) can be neither a Rufous nor a Mottled grasshopper. Furthermore, viewed from above (photo 2 , click to enlarge) you can also make out the raised "shoulder blades" ('the keels of the protonum'). The fact that these are curved, rather than straight, also means we can dismiss the possibilty of my grasshopper being a Lesser Marsh.

Unfortunalty, some other features (such as the wing veination) that would have clinched the identity of my grasshopper, I wasn't able to get from my photos. Luckily however, the photo on the front cover of Dr. Mahon's book seems a very close match for my grasshopper - so on that basis I'm going with the Common Field. I say 'luckily' as the Common Field shows considerable variation in patterning and coloration as the photo's here prove. Without the picture on the front of Dr. Mahon's book I might have struggled for longer...always assuming of course I'm now correct! If you know for certain please do leave a comment.

Saturday, August 4, 2007

Cultivated Oat Avena sativa

I am an amateur naturalist trying to learn a little about everything that lives in my garden.

A small clump of oats is growing in my garden (at (0.8,0.6) - see here). Since this spot is below my bird table where I hang a feeder of mixed seeds, I suspect they sprouted from the fallen seed.

A number of oat species are found in Britain and I understand that hybrids are not uncommon. I don't have the expertise to identify my oat with absolute confidence, but I'm going with the Cultivated Oat (Avena sativa) based on the smooth, hairless spikelets (the 'heads' in photo 1) and description in my copy of Grasses (Fitter, Fitter, Ferrer, publ. Collins).

In my last posting I spoke of my pleasure of learning for the first time that grasses are flowering plants. Old news to you all out there I'm sure - previosuly I'd not taken the time to register grass as being anything more than 'green stuff' (though in retrospect I admit the fact that grasses produces pollen, hence hay fever, ought to have been a pretty big clue).

If there is an excuse for my ignorance, it is that grass flowers tend to be rather tiny, unfamiliar in appearance and get labelled with a complex terminology. Having acquired my new knowledge however, I have been determined to get to grips with the details, and accordingly Photo's 2,3 (click to enlarge) show my attempt to dissect an oat spikelet. I don't doubt for a moment that exactly the same subject matter is presented, and better, in innumerable botany text books out there. Since I'm trying to learn a little about the natural history in my garden for myself however, and blog my experience of doing so, I don't feel the need to apologise for repeating it here. So there!

The two outermost 'leaves' (except they're not true leaves) of a grass spikelet are called the glumes. The two may differ in length (which can be a useful clue when trying to decide the species of a grass). The glumes enfold one or more florets each of which consists of a two leaf-scales called the palea and the lemma. A long thin awn may emerge from the lemma.

In between the palea and the lemma (see photo 3) sit the anthers and ovary (the male and female reproductive parts of the grass). It is the anthers that split open to liberate pollen. Under a microscope (photo 4, 40x magnification) you can see one of the yellow anthers doing just that.

And that, as they say, is that! In all however, probably best to stick with roses for those special occasions: I find a box of porridge oats tends not to have the same impact.

Thursday, August 2, 2007

Barren Brome Bromus Sterilis

I am an amateur naturalist attempting to identify every living creature in my garden.

The wonderful thing about being an amateur is that you get to discover so much. For example, in preparing for this posting I have made the astonishing discovery that grass is a flowering plant! Hitherto, I have to say I had assumed that flowering plants had obvious flowers, and that grass, well... green stuff. I confess, I do have a suspicion that the botanical community might just have beaten me to my discovery!

Until recently you could find a clump of grass growing in my garden at (0.6,0.8) (see here). I say 'until recently' as my grass is an annual: the photo left (click on photos to enlarge) was taken back in May. Having set seed, the clump has since died back.

Photo 2 gives a clearer view of one stem. Botanists refer to the "busy area" at the top of the stalk (the 'culm') by the lovely name "a nodding panicle".

According to my copy of Grasses (Hawley, Shire Nat. Hist.), more than 150 species of grass grow in Britain. So, how do you set about identifying the species of the one you happen to be looking at? Answer: first, find your ligule! No, prior to my preparation for this posting, I didn't know what a ligule was either. A ligule, it turns out, is a small, semi-translucent, vestigial leaf-like structure that sits at the junction between the stem and each of the leaves. You can see one in photo 3 (the little white pointy thing). It turns out that the nature of the ligule (pointed or blunt; ragged or smooth; present or absent etc.) is a useful species clue. Others include the presence or absence of hairs on leaves or stem, the dimensions of leaves and stem, and of course the nature of the panicle (for example, in some grasses, a compact spike; in others, as here, a nodding panicle).

Noting the hairless stems, downy leaves, pointed ligule, the purplish colour of the lower culm and various other features, and working with my copy of Grasses (Fitter,Fitter,Ferrer; Collins pocket guide), and the photo's in Grasses,Ferns, Mosses and Lichens (Roger Phillips, Pan Books) I'm fairly confident in identifying my grass as Barren Brome (Bromus sterilis).

Returning to the issue of grasses being flowering plants mentioned in the first paragraph, photo 4 shows a closeup of one of my grass's spikelets. The spikelets are, in a sense, the rather complex flower-heads of grasses. There is a complex set of terms (awns; lemmas; glumes and paleas to name a few) that identify all the various parts of a spikelet. The awns, for example, are the long bristles seen in the photo emerging from the ends of the spiklet. Hidden amongst the complexity of the spikelet are the tiny pollen-bearing (hay-fever causing!) anthers and female ovaries of the grass, that make up a grass flower. I have not gone to the trouble of dissecting out and photogrpahing all these various parts, but it is something I hope to return to in a future posting.

Finally, regular readers will know I'm fond of viewing things under my microscope. Clicking on the photo above to enlarge you'll note the presence of a number of tiny grass seeds. Photo 5 shows two viewed at 40x magnification. I'm intrigued by the seeds' concave 'boat-like' shape and wonder what purpose it serves for them to be shaped like this. I've read that some plant seeds are cleverly shaped so that, when lying on the soil, if they are subjected to random 'jostling' (say, by a passing breeze) they act like little corkscrews and quite literally drill themselves down into the soil. I wonder whether the shape of my grass seeds indicates they are of this type. On the other hand the explanation might be something else entirely. If anyone out there happens to know, do please leave a comment.