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.

Congo Cockatoo, Impatiens niamniamensis,Balsaminaceae

Flowers don't come much gaudier than this - primary colours straight out of a child's paintbox. It reminds me of some of the more lurid boiled sweets I used to buy in the sweetshop on my way home from school.

Impatiens niamniamensis comes from tropical Africa, from montane regions of Cameroon, extending through central and East Africa where it's used medicinally to treat migraines and painful joints. It makes a spectacular house plant, with one significant drawback - it seems to be extremely susceptible to pests like whitefly and red spider. The only way I've been able to cultivate it for any length of time without it resembling the contents of Pandora's box is to frequently root new plants from clean cuttings.


The flower has a very long, curled nectar spur and I've found a few sources that suggest that it's pollinated by birds - bright red flowers are often associated with bird pollination.

A big specimen in full flower makes a fine spectacle, resembling a tree full of parrots. There was a time, when I set out in gardening, when I was primarily interested in species with subtle, muted colours but these days I'm increasingly drawn to flowers whose colours are so hot you could warm your hands on them; maybe it's a symptom of advancing years..........

Woad, Isatis tinctoria, Brassicaceae

About twenty years ago I fancied trying my hand at dyeing ..... and where better to start than with indigo extracted from woad? The woad seeds germinated well, the plants (which are biennial) flourished but somewhere along the line I lost enthusiasm for the enterprise - perhaps when I realised how much woad I'd need to grow to produce a worthwhile amount of dye and what a messy business it would be. You can find a description of the whole process here.


 So the plants ran to seed, after producing a spectacular display of small flowers that were very popular with hoverflies. Even today, two decades later, occasional seedlings from those original plants appear in the garden so my redundant woad crop must have left a persistent seed bank.


Woad has been used as a source of blue dye since ancient times (for a detailed account click here) but was superseded by true indigo Indigofera tinctoria which in turn was replaced by modern synthetic indigo dyes.

Fritillaria michailovskyi, Liliaceae

There are over 100 species of Fritillaria and I think this one, F. michailovski, was the first I ever encountered, in the alpine house at the RHS Garden at Wisley, about 50 years ago. There was something about the weird colour combination and art deco lampshade form of the flowers that really appealed to me but it was another 40 years before I got around to growing it for myself.  These days the bulbs are more easily available and considerably cheaper than they were half a century ago. The species comes from the high mountains of North East Turkey and performs best if it's grown in an alpine house, in a  pan of free draining compost topped with grit.

F. michailovskyi is one of the smaller species in the genus and this is the largest, the well-known, 1.5m. tall crown imperial F. imperialis, whose regal appearance is somewhat undermined by its unpleasant foxy smell. This unfortunate aroma may be the source of the belief that the plant repels mice and moles, that presumably think they are in the presence of a sharpd-toothed predator when they smell the plant. There does seem to be some evidence that the plant repels deer, that reputedly avoid it, and some recent biochemical analysis of the plant's nectar has identified the evil-smelling compound responsible as 3-methyl-2-butene-1-thiol, which I imagine could be the basis for a deer repellent if the effect is as strong as some people claim. Crown imperials grow wild in Turkey, Iran, Afghanistan and Kashmir.

William Robinson, in his celebrated The English Flower Garden, commented that most fritillaries have "dull tinted curiously interesting flowers" and that is particularly true of F.camschatcensis from Japan, Kamchatka and Eastern Siberia. In some forms of this plant the flowers are almost black but their other striking feature is a stench that is said to be truly disgusting. It's a plant for humus-rich soil in light woodland shade. Apparently the bulb is edible and is said to taste like roast chestnuts but I wouldn't be tempted to risk it since several Fritillaria species are known to contain physiologically active substances or are downright poisonous, including ....

... the familiar snake's head fritillary, F. meleagris. Like all fritillaries that I have ever grown this is an extravagant producer of nectar and is very popular with bumblebees when it flowers in my garden in late April. I've been growing it for about 20 years and it now seeds itself around the garden, often in unexpected places, but one of the best ways to grow it is in grass, as William Robinson recommended back in 1883: "It grows freely in grass not mown early", he wrote," and is therefore admirable for the wild garden; its various forms are amongst the most beautiful inhabitants of the hardy bulb garden, and tufts of the chequered or white-flowered variety are amongst the most graceful plants in cottage gardens".

Fairchild's Mule...... almost

Thomas Fairchild (1667-1729) was a nurseryman from Hoxton who is credited with producing the world's first deliberate man-made hybrid plant, when in 1717 he crossed a carnation (Dianthis caryophyllus) with sweet William (D. barbatus) to produce a sterile hybrid with intermediate characteristics. He presented a pressed specimen to the Royal Society and you can see an image of what I assume is the same herbarium specimen here. 

Being a devout church-goer and believer in divine creation, Fairchild was perturbed by what he had done, which carried a whiff of blasphemy about it, and perhaps to atone left a  bequest to his parish church (St.Leonards in Hackney Road) for an annual sermon on the 'wonderful works of God' which is still delivered annually, at Whitsun, to the Worshipful Company of Gardeners, decked out in their ceremonial gowns, although the venue is now St.Giles, Cripplegate. You can read more about Fairchild here , where there is also a photograph of his gravestone.

Fairchild's experiment was a landmark in plant science, ushering in an era of controlled hybridisation between plant species that has resulted in many of the garden plants that we now grow - and also many important crops. 'Mule', incidentally, as a term for a sterile interspecific hybrid, still persists in animal breeding circles. When I was a child my grandmother kept a goldfinch mule - a purported hybrid between a goldfinch and a canary that was supposed to sing better than either parent.

I've long been intrigued by Fairchild's mule and have often wondered whether one of the parents was indeed a carnation or perhaps might have been a garden pink D.plumarius, which was a popular plant in Fairchild's day, easier to grow, much appreciated for its carnation scent and often referred to in old gardening books and in popular parlance as a 'carnation'. Fairchild almost certainly grew pinks and it's hard to believe that he would not have tried making hybrids with those - especially as they bloom at the same time as sweet Williams.

Anyway, here's my attempt at producing a modern-day equivalent of Fairchild's mule, raised by crossing a garden pink Dianthus plumarius with sweet william D. barbatus, with the former as the female parent. Like Fairchild's mule it turned out to be sterile but was easy enough to propagate from cuttings. I tried to backcross it to both parents but couldn't produce any seed from either of those crosses.... presumably because the hybrid's pollen was sterile.

My mule was very tough little plant with wiry stems - very reminiscent of the herbarium specimen mentioned above and of published descriptions of the original hybrid. It was incredibly floriferous, with every hybrid I raised having the same magenta flowers, which didn't have much detectable scent. It flowered perpetually through the summer and I had difficulty in finding non-flowering shoots to root as cuttings. Eventually it literally flowered itself to death.

This year I'm planning to have a go at producing a  proper Fairchild's mule using carnation rather than a pink as a parent, to see whether it resembles my earlier attempt using a pink. It requires much more effort to grow carnations than to grow pinks, though.

In 2000 Michael Leapman published a detailed account of Fairchild's life and work, entitled The Ingenious Mr. Fairchild: the Forgotten Father of the Flower Garden (Headline, ISBN 0747273596) - well worth reading if you can find a copy.

Solanum lycopersicum, Tomato, Solanaceae

My mother always told us not to play with our food when we were kids but when you're a grown-up botanist you just can't help yourself: it's so interesting. I doubt whether zoologists get quite so much pleasure from this activity because animal food is usually dismembered and cooked to oblivion, whereas a lot of the plant food that we eat is more of less intact and open to easy investigation.

This slice of tomato, Solanum lycopersicum, eventually destined to be part of my BLT, shows the essential characteristics of the fruit, which is botanically a berry - defined as a fleshy fruit derived from a single ovary. In the tomato's case it's a multi-seeded berry, with each of the numerous individual seeds attached to the central placenta via its own vascular supply. You can see in this section that the fleshy fruit wall - the pericarp - is divided into distinct layers: the outer exocarp (with more concentrated  red pigment); the mesocarp; and the endocarp which is partly juicy and fills the fruit chambers (loculi) that surround the seed. 

It has all evolved to attract a hungry animal and those seeds in the fruit loculus are perfectly capable of passing through the mammalian gut unharmed. That's why feral tomato plants are often a prominent feature of sewage farms. Seeds of the distinctive yellow fruits of the Galapagos tomato, Solanum cheesmaniae, endemic to those islands, are eaten by Galapagos giant tortoises that disperse the seeds (slowly and not very far away) in their droppings. 

Tomatoes are said to have been introduced into Europe by the Spanish conquistadors, who found that they were already widely cultivated by Mesoamerican civilisations when they arrived in the New World. For centuries tomatoes were viewed by Europeans with suspicion and considered to be poisonous. Somehow the idea that they were aphrodisiacs arose, first in Italy then in France and finally in England and they became known in all three languages as 'love apples'. The term persisted for a long time and in my copy of Everyman His Own Gardener:The Complete Gardener, written by Thomas Mawe and John Abercrombie and published in 1855 - and which you can download here - they are still referred to both as 'love apples' and tomatoes, although by that time their tasty flavour and nutritious qualities were recognised.

Modern cultivated tomatoes tend to be reliably self-pollinated, with their stigma hidden inside a ring of stamens that shed pollen directly onto its surface, but in wild species the stigma protrudes well beyond the end of the stamens and requires an insect to transfer pollen to it. This is the flower of a cultivated tomato, with the anthers just beginning to shed pollen onto the stigma hidden within.


Part of the pleasure associated with eating a tomato comes from the aroma, which is always far inferior in supermarket chiller-cabinet fruit to the sensory qualities of a warm, ripe tomato picked directly from a plant on a summer's afternoon. That alone makes them worth all the effort needed to grow them, even though it's more expensive to do so. I like the smell of the plants as well when you brush against them in the greenhouse and much of that emanates from the surface hairs, or trichomes, which cover most of the plant. 

There are two kinds of trichomes on tomatoes - long, simple hairs and short glandular hairs whose heads of swollen cells are filled with aromatic compounds.

You can see both here, on a flower pedicel, with the very short glistening glandular hairs covering it's surface.

Here, at higher magnification, you can see just how densely packed they are. Some tomato genotypes have glandular trichomes that contain particularly high concentrations of insect-repellent volatiles, and there's now a lot of interest in transferring this characteristics to cultivated tomatoes, to reduce the need for growers to use chemical pesticides to tackle aphids, red spider and white fly, which can blight the life of an avid tomato grower.

Starfish Flower, Stapelia variegata, Apocynaceae

Stapelia variegata belongs to a select group of  plants with sapromyophilous flowers - flowers that mimic the scent (and sometimes colour and texture) of carrion, attracting fly pollinators that are deceived into laying eggs on them and accidentally pollinate the flowers as they do so. The odour of flowers with this pollination syndrome can vary - from mildly unpleasant (as in the case of S.variegata, where you need to be quite close to detect it) to truly nauseating (as in the case of Dracunculus vulgaris).

The surface of starfish flower feels like wrinkled flesh and those brown spots are rather similar to the early symptoms of putrification in a pale-fleshed corpse.The inner parts of the flower - known as the corona - are surrounded by a raised ring called the annulus and consist of five horizontal bifurcating segments and five bifurcating, upright horn-like structures, which together appear to guide wandering flies towards the functional reproductive organs, although it's not clear exactly how they do this. The male anthers on the inner corona lobes are in the form of a pollinium so are carried off in their entirety on the leg or proboscis of a visiting fly. The stigma is located within the outer corona lobes, which guide the pollinium attached to a visiting fly onto the stigma surface. You can read a plant breeder's account of Stapelia flower structure and pollination here.


Stapelia is a predominantly South Africa genus of succulent plants which used to be classified within the family Asclepiadaceae (milkweeds). This species is very easy to cultivate as long as it's planted in a well drained compost and not overwatered. This is also an easy species to raise from seed - which is worthwhile because the mottling on the flowers is quite variable - so amongst a batch of seedlings you might find something unusual and interesting.