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Friday, November 9, 2012

Kniphofia spp., Red-hot Poker, Xanthorrhoeaceae, sub-family Asphodeloidea

It came as a surprise to me that red-hot pokers thrive in my garden here in North East England. If you look at the distribution map of the species, through Africa and Madagascar, with an outlier in Yemen, you'd imagine that heat and dry conditions are a requirement but when you look at the habitats occupied by many of the species - cooler, higher altitude sites - maybe it's not so surprising that they do well in my flower borders. This summer, which was cool and wet, seems to have suited them pretty well......

.... especially this yellow-green flowered variety. I've lost its label but I think it might be 'Percy's Pride'. This plant produced 15 flower spikes and was in bloom for six weeks.

The best display of Kniphofia uvaria that I've ever see in Britain is this one, in the sand dunes on the Northumberland coast at Low Newton-by-the-sea where it is verging on becoming invasive  They're not the conditions that would be easy to replicate in most gardens though.

I'm always interested in the native insects that visit exotic flowers in British gardens. In its native habitats Kniphofia is pollinated by sunbirds and each individual flower produces a large volume of nectar to attract these energetic pollinators. The nectar must trickle down those long, downward-pointing tubular flowers, because peacock butterflies seem to have no trouble in reaching it.

Access is more of a struggle for wasps, which will do almost anything to reach sweet nectar in autumn when they are no longer feeding their brood. This enterprising individual discovered that the easiest way to reach a reward was to chew a hole through the corolla ...... 

...... while this one chose to do it the hard way, forcing its way into a flower that really evolved to accommodate a sunbird's long, slender, curved beak.

Friday, August 10, 2012

Masterwort, Astrantia maxima and A. major., Umbelliferae

Ever since masterwort Astrantia major was introduced into British gardens in 1597, from its native central and eastern Europe, garden writers have been somewhat dismissive of the plant. William Robinson, in The English Flower Garden in 1883 was wary of its invasive tendencies (".... apt to over-run and exhaust the soil") and suggested that "if grown at all it should be in rough or wild places, or in the back part of the shrubbery". 

However, the species in the picture above, Astrantia maxima, is rather more delicate and trickier to cultivate, so is unlikely to be invasive. It needs better, more moisture-retentive soil than A. major.

It's easy to see why the more commonly cultivated A. major  was sometimes known as 'hattie's pincushion" and why Graham Stuart Thomas, in his Perennial Garden Plants (1976) described the flowers as having " interesting and beautiful shape". . 

It isn't obvious that this is a member of the Umbelliferae but if you shrink that ring of papery bracts and elongate the pedicels that support the individual florets the result is a more obvious umbel.

The plant has a long flowering period, seems to do well in sun, shade and dry soil in my garden, makes an attractive long-stemmed addition to a bunch of cut flowers and, best of all, is an excellent source of pollen and nectar for .....

... hoverflies ....

                 ..... and bees, that merely need to walk over the inflorescence to collect their reward with minimum effort. 

Monday, July 16, 2012

Monk'shood, Aconitum napellus, Ranunculaceae

"Helmet-fluore, or the great Monkes-hood, beareth very faire and goodly blew floures in a shape like a helmet; which are so beautifull, that a man would think they were of some excellent vertue, but non est semper fides habenda fronti " wrote John Gerard in his herbal of 1597. And, indeed, appearances are not always to be trusted, because Gerard then went on to describe the dire consequences of eating this poisonous member of the buttercup family. "The force and facultie of Wolfs-bane [another common name for members of the monk'shood genus] is deadly to man and all kindes of beasts .......The symptoms that do follow those that doe eat of these deadly herbs are these; their lips and tongue swell forthwith, their eyes hang out, their thighes are stiffe, and their wits are taken from them.

But as long as you don't eat it, this is a fine plant for the herbaceous border, with the flowers of a violet-blue hue that's shared by wild columbine, another member of the same plant family.

Gerard noted that the plant was also found in alpine meadows "where you shall find the grasse that growth round it eaten by cattell, but no part of the herb it selfe touched, except by certain flies, who in such abundant measure swarme about the same that they cover the whole plant". He then describes how a confection made from twenty of these flies that are immune to monk'shood's poison was an "excellent  remedy not only against the Aconites, but all other poisons whatsoever".

Looking at the rather sinister flowers from the side, it's easy to see where the names helmet-flower and monk'shood came from.

The nectaries of the flower are located way up inside the upper petal that forms the hood, where only long-tongued bees can reach it.

The flower is dependent on bumblebees for pollination and the strong bilateral symmetry of the flower means that they have to force their way in through this narrow opening, where they brush against the stamens and stigma as they struggle to reach the nectaries in the hood. The stamens ripen before the stigmas (protandry) and in this picture you can see a couple whose anthers have burst, shed their pollen and whose stamen filaments have elongated. There are six more whose anthers have burst to release white pollen but whose stamen filaments haven't elongated, but the majority of the numerous anthers present have yet to release their pollen.

I've posted some photos of bumblebees visiting the flowers here.

Friday, July 6, 2012

Giant Fennel, Ferula communis, Umbelliferae

I've waited seven years for this.

Back in 2007 I bought a small plant of giant fennel Ferula communis, when I was mainly attracted by its delightful, ferny, four-pinnate foliage but also tempted by the promise of a giant inflorescence.

Every year since then it has produced a few magnificent leaves, almost a metre across, but has never showed any sign of flowering. Finally it has summoned up the energy to perform, which is remarkable on two counts. 

Firstly, this is a plant from dry, rocky places in the Mediterranean - in countries like Greece - and this is cold, rainy Durham in northern England, in the grip of the wettest summer on record. 

This is its natural habitat (image source

Secondly, according to Marjorie Blamey and Christopher Grey-Wilson's Mediterranean Wild Flowers:

'The stems becomes hard and woody on drying ..... the pith, when dry, burns slowly inside the stem and can be carried alight - it may well have been the original Olympic torch'.

And, of course, this is the year when the Olympics come to Britain. Nice timing!

Other sources claim that the stems were used by Prometheus when he stole fire from the gods on Mount Olympus and gave it to humans.

The stem is robust - and has been used for making furniture, apparently - and the leaf bases sheath the stem in this very distinctive manner.

The inflorescence finally finished elongating when it was close to three metres tall ....

...... then its yellow umbels bloomed. The only way to photograph these is from the upstairs bedroom window......

........... although they do look attractive from below, against the sky.

It's also a very good 'bee-plant' attracting a constant procession of bumblebee visitors to these umbels, each of which is as big as my fist.

Worth waiting for!

Giant fennel is monocarpic and the plant will die after flowering, but I'm tempted to try that stem as a home-made Olympic torch....

Sunday, June 10, 2012

Lupin, Lupinus spp., Fabaceae

June is the peak month for lupin flowers, although they don't seem to be such popular border plants as they once were. 

We have a family connection with lupin growing because in the 1920s my grandmother worked in Drayton Manor nursery, near Chichester in West Sussex, that specialised in growing Lupinus polyphyllus as a cut flower. This is a photo from the nursery catalogue, although the lady isn't my grandmother. The fields of flowers must have looked spectacular and I can remember as a child seeing feral descendants of these plants growing on the edge of gravel pits where the nursery once stood, and seeing them in Gran's garden. The sweet peppery scent of their flowers always triggers recollections of these stately blooms, with bees working their way methodically around and up each flower spike before moving on to the next.

Lupinus polyphyllus, which is naturally blue-flowered, was introduced from North America by the plant collector David Douglas in the  1820s and soon became a popular subject for the herbaceous border, which it graced until the Yorkshire gardener George Russell decided to try to produce plants with denser flower spikes in a wider range of colours.

Beginning just before the First World War, Russell grew thousands of lupins on his allotment and ruthlessly eliminated any that he thought sub-standard, favouring bi-coloured forms with closely spaced whorls of flowers on the flower spike. By the late 1930s he'd produced his famous Russell lupin strain and with the help of nurseryman James Baker propagated the best forms commercially from cuttings. The plants were a sensation at the 1937 Royal Horticuultural Society Chelsea Flower Show and Russell, at the age of 79, became famous, receiving an MBE and the RHS Veitch Memorial Medal for his efforts. He lived on until 1951, dying at the age of 94. Plant breeders do seem to live to a grand old age; perhaps it's the determination to see how seedlings from last year's cross pollinations will perform.

Russell probably intercrossed L. polyphyllus with other species (possibly with tree lupin and the annual L. nootkatensis) although we can't be sure because no pedigrees of cross pollinations were kept. It seems likely that he probably let bees do the intercrossing for him.

For anyone with space enough to grow the plants, breeding lupins can be rewarding , as the seedlings flower in the year after sowing. Crossing involves carefully emasculating the flowers while they were still in bud, by carefully opening the buds and removing the stamens before they can shed pollen and then, after a delay while the flower develops and the stigma matures, cross pollinating the stigma with pollen from another individual, or even another species which may or may not produce a viable hybrid seed. 

Lupin flowers, like most legumes, have a distinctive and instantly recognisable flower morphology, with a prominent standard petal at the top and a folded keel petal, enveloping the stamens and the stigma, that's flanked by a wing petal on either side.

You can always spot a lupin flower that has been 'tripped' by visiting bees because their weight forces down the wing petals so the pointed tip of the keel petal protrudes.

During the bee's visit the keel petal is pushed downwards so the stigma at the tip of its long style is forced up through the end of the keel, sweeping a plug of pollen from the anthers before it and onto the underside of the bee. You can see the pollen as the yellow deposit on the tip of the keel petal and on the stigma in this photograph. 

Plentiful pollen makes lupin flowers very attractive to bumblebees, so emasculated, cross pollinated flowers need to be covered to keep bees away until seed has set.

The most interesting lupin species that I've grown is this one - Lupinus mutabilis. It's an annual that comes from South America, where it's known as tarwi and is said to have been cultivated as a food crop by the Incas. It's seeds have very high levels of protein (40%+) and lipid (20%+) but from the horticultural point of view it's the colour and fragrance of the flowers that appeal. It's easy enough to grow provided you don't attempt to transplant it. It never recovers from the slightest root disturbance, so you either need to raise it in pots as a conservatory plant or sow it in the garden where you want it to flower.

Tuesday, May 1, 2012

Prickly pear, Opuntia macrocentra, Cactaceae

A large prickly pear cactus, like this Opuntia macrocentra that comes from the Pecos region of Texas, is a thing of beauty when in full flower - although those long sharp spines can also inflict acute pain. 

These magnificent flowers only last for a day and change colour to a more orange hue after pollination, which is apparently performed by bees. You can read an account of the pollination ecology of the plant here.

The fruits that form after pollination are edible in some species of Opuntia, notably O. ficus-indica, and marketed commercially as tunas that are popular in Mexico and occasionally appear on British supermarket shelves.

The stamens shed pollen soon after the flowers open in the morning but the stigma only becomes receptive in the afternoon and must be cross pollinated with pollen from a different individual plant before the flower will set seeds. The stamens are touch-sensitive, curling towards the stigma if you give them a gentle poke, mimicking the action of a visiting bee.

Flattened, jointed, photosynthetic stems called cladodes take over the function of leaves in prickly pears and most species defend themselves with long, sharp spines against grazing animals. These often have clusters of tiny, barbed hairs called glochids around their base and these are acutely irritating if the stick in soft flesh - like lips, for example. In a few species, like ...

...... this O.rufida the long spines are entirely replaced by vast numbers of glochids arranged in dense clusters called areoles. The glochids are ....

... easily detached and break off at the slightest touch, so gently brushing against one of these glochid-covered cladodes can be a very unpleasant experience. For a really close look at these nasty microscopic harpoons, click here.

Both species illustrated here are growing in the desert house in Durham University Botanic Garden.

Friday, March 30, 2012

Magnolia stellata, Magnoliaceae

If we had enough space in our back garden I would plant one of the large flowered, tree-sized Magnolia species or hybrids - probably M. x soulangeana - but we only have room for the Star Magnolia, M. stellata which comes from Japan and produces many fine flowers on a relatively compact plant. It's the earliest-flowering magnolia and the weather here over the last week, which has been unremittingly warm and sunny, has been kind to the 15 year-old specimen in garden. In a couple more days it will be at its best, but  four days from now temperatures are forecast to plummet, with maybe even some snow, so the current pristine display of flowers will probably suffer from some frost damage by the middle of next week and those pure white tepals will be scarred with brown patches. 

Part of the pleasure from growing this plant comes from watching the attractive furry flower buds swell, bringing a growing sense of expectation. When the bud scales part and the pink tepals begin to force their way out, you know that spring is gathering pace.......... but anticipation is tempered by the knowledge that spring can be fickle. It looks like this year's display of starry flowers will be short-lived...... but spectacular while it lasts.

Sunday, March 25, 2012

Garden Seats

Long ago I promised myself that the next garden I have will be designed around the seating. Before I do anything else I'll identify the places that provide the best morning, afternoon and evening viewpoints and choose some comfortable seats where I'll be able to rest my weary limbs and admire my handiwork over a glass (or two) of wine. But generally speaking garden seating tends to be designed for looking at rather than sitting on and is often excruciatingly uncomfortable, unless you carry a pile of cushions around with you. Here are four attractive seats that are fine for a Digital Botanic Garden, but not much good for sitting on for any length of time. 

Edwardian cast iron fern seat - lovely to look at but cold and very uncomfortable...

... lichen covered bench - obviously the gardener here was always far too busy to sit down.....but the seat really adds character and maturity to a garden.... 

 .... follow the sun - wheel this one around your extensive acres in search of the best place to linger ... but not for too long on its hard wooden surfaces...

.... and a painfully intricate creation in cast iron, in a sun-trap surrounded by Caenothus and Wistaria....

Tuesday, March 20, 2012

Azara microphylla, Box-leaved azara, Salicaceae

For most of the year Azara microphylla isn't a very impressive plant - just a rather straggly shrub with masses of small, glossy leaves - but for a couple of weeks in spring it reveals a rather delicious attribute: a powerful aroma of chocolate. It produces clusters of small golden stamens from the beginning of March onwards and when I opened our back door this morning (which is the day of the vernal equinox - the first day of spring) I was greeted by the chocolate scent that the Azara that's trained against the wall was releasing in the early morning sun.

The precise perception of scent is a personal attribute and I know some people who find that, to them, it smells of chocolate. Scents are often closely interwoven with memory and to me the aroma is reminiscent of the smell of a brand of chocolate called Caramac that I was very partial to in my youth.

If you are a chocoholic gardener you can find information on cultivating Azara, which can become a small tree, here and you can find more photographs here. Sadly the web is useless for conveying scents but if you can locate a bar of Caramac you'll see what I mean about the aroma .....

It is a native of Chile.

Friday, March 16, 2012

Rhododendron dauricum, Ericaceae

I'm not a great fan of some of the overblown garden hybrid Rhododendrons but Rhododendron dauricum is always a welcome sight. It's an early bloomer - not surprising when you look at its natural geographical distribution, across northern Russia, China and Japan - and it has been flowering in my garden since the beginning of March.

The fact that it flowers on almost bare twigs enhances its beauty and no doubt ...

.... makes it more conspicuous to the first queen bees that emerge in spring from hibernation to collect nectar from the flowers. This Rhododendron species and many others in the genus have a particularly unusual way of dispensing pollen to visiting insects.

In many plants the anthers at the tip of the stamens simply burst open and expose all their pollen at once, but R.dauricum anthers dehisce through a small pore at the tip - which you can see clearly in the lower-most anther in this picture. The buzz of bees visiting the flowers makes the stamen filaments vibrate with a similarly high frequency, shaking pollen out of the pore a little at a time - which is an economical way of distributing the available pollen to as many bumblebee visitors as possible during the long flowering period in spring.