Sparmannia africana, African Hemp

All plants are capable of gradual movement as a result of slow growth, but relatively few species can make the kind of rapid movements that we tend to associate with animals. The Venus fly trap Dionaea muscipula and the sensitive plant Mimosa pudica are the two species with rapid leaf movements that are most familiar but another fast-mover is African hemp Sparmannia africana. If you gently brush the cluster of golden stamens in the centre of the flower nothing happens for a second, than they move outwards, away from the stigma. The time delay between the photo above and that of the same flower whose stamens have been brushed, below, is about five seconds and you can easily see how the stamens have spread apart.

Presumably this is some kind of mechanism to aid pollination, although how it would do that isn't obvious. Similar stamen movements occur in Mahonia and Berberis flowers, although in those cases the stamens move rapidly inwards when they are stimulated.

Sparmannia africana comes from South Africa and makes a very fine house plant - if you have room for it. My plant grew too big for our conservatory and is now in Durham University Botanic Garden, where it has reached about three metres in height and is currently flowering and setting seed.

Mutants and Monstrosities

You don't need to be a gardener for very long before you discover that within every species there are always a few plants that don't conform to the norm. They're either mutants (where changes in their genes produce a different shape, form or colour of plant) or they're monstrosities (where there some external agency, like environmental stress or disease has led to abnormal growth).

Only mutants produce heritable changes, that will be passed on to at least some of their progeny. I would guess that the abnormal ox-eye daisy (Leucanthemum vulgare) above is a mutant. Some of its florets are spoon-shaped and since this abnormal plant turned up in my garden a few years ago others have appeared in subseqient years with the same characteristic, probably arising from seeds produced from those abnormal florets. Cultivars of a number of daisy-like species that have flowers composed entirely of spoon-shaped petals have been bred, so it's highly likely that this is a genetically controlled change in the pattern of petal development.

I'm pretty certain, on the other hand, that this two-headed ox-eye daisy is a monstrosity, the result of some agency that has interfered with the normal development of the flower and produced twin heads. Temperate-shock (i.e. frost) can sometimes do this.

This monstrous spear thistle Cirsium vulgare is the result of several flower heads becoming joined, side by side into a cock'scomb-like inflorescence, probably as a result of either stress during a critical phase of flower bud development or perhaps infection with a bacterium - Corynebacterium is known to cause a similar phenomenon, known as fasciation, in ...



Linaria purpurea...

Forsythia x intermedia, where it causes a switch in symmetry of the stem, from radial symmetry to flat, plank-like growth...

... and occasionally in herbaceous species like candelabra primulas ......

Some mutant forms of growth are widely cultivated for human consumption, like the cauliflower - which is a mutant inflorescence where the flower buds proliferate to the extent that they can no longer open properly.

My favourite monstrosity, though, is to be found in foxgloves Digitalis purpurea, where occasionally the last flower to form at the top of the floral axis results from fasciated growth of several flower buds. If you compare the monstrous flower on the left with the normal one on the right you can see that it has four stigmas, styles and ovaries, within a single tubular corolla - four flower buds fused to form a single flower.

Seeds

Since this is the time of year when most plants in my part of the world are setting seeds, I thought I'd post a few images of these wonderful objects. This is one of the ripening seeds from my runner beans Phaseolus coccineus, with the testa and one of the cotyledons removed, revealing the embryonic plant inside. The cotyledons contain the store of proteins, carbohydrates and lipids that will provide sustanance for the germinating seedling until its first true leaves unfurl and begin to photosynthesise. In this image you can see that the rudiments of the venation in those first true leaves, that will transport sugars to other part of the young seedling, have already formed in the embryo. The embryo is attached to the cotyledons at its hypocotyl and the embryonic root points downwards and to the left. 

There's a heavy crop of oak (Quercus spp.) acorns in this part of Durham this year - it's a mast year. Oak acorns - technically nuts - germinate soon after they fall to the ground, anchoring themselves via their root but then suspending further growth until spring, when the shoot forms. If you are planning to plant oak trees, it's best to sow the fresh acorns soon after they fall.

Once seeds germinate their root needs to spear into the soil quickly, driven by the hydraulic force inside expanding cells. Here you can see the glistening root cap of a maize (corn) Zea mays seedling, producing the mucilage that lubricates its path between the abrasive soil particles. Further back, you can see the forest of root hairs, each a single elongated epidermal cell that makes intimate contact with the surface of soil particles and absorbs water and soluble minerals. Each root hair has a short life span, of perhaps a day, and new hairs are formed constantly behind the advancing root tip; collectively they constutive a vast absorptive surface.

Cyphostemma juttae, Vitaceae

About 20 years ago a South Africa botanist gave me a few seeds of this strange succulent, Cyphostemma juttae, which grows in rocky, arid parts of Namibia. It has taken all that time for the seedling to reach this size - about 70 cm. tall - on my windowledge and since it can grow to 2.5 metres tall in the wild it's still got some way to go, although it's under less than ideal conditions, in a flower pot.. Every winter it sheds those succulent leaves completely, leaving only the swollen stem - known botanically as a caudex - then regrows leaves in late spring. It first flowered about five years ago, but this is the first year that the flowers have produced fruits.

The stem constantly sloughs off layers of papery epidermis, which I suspect might have some role to play in reflecting intense sunlight.

The thick, lobed succulent leaves have a saw-tooth margin and each leaf lobe is about 15cm. long.

These small, glassy beads appear on the underside of the leaves, soon after they've fully expanded.

I've yet to discover whether they are crystalline sugar or resin - I suspect they are the latter.

One of the most remarkable aspects of the plant is that it is in the grape family and is commonly known as the Namibian grape or tree grape. You'd never suspect that until you take a look at the fruits, which turn purple when they ripen, but unlike the edible grape they are poisonous.

Saponaria officinalis, Soapwort and Quinoa Chenopodium quinoa

If you are looking for a plant that has good credentials for inclusion in a wildlife garden, then soapwort Saponaria officinalis comes close to being a strong candidate - but with one serious drawback. In my experience its rapidly-elongating rhizomes make it very invasive.

Back in 1999 a trial of 25 native plant species carried out at the University Botanic Garden at Cambridge ranked soapwort was the second most popular nectar source for butterfly species,  with a very high nectar secretion rate and second only to purple loosestrife Lythrum salicaria in the number of butterfly species that it attracted. Not only that - it's also virtually slug-proof. Recently researchers in Poland have shown that slugs avoid eating soapwort.

Soapwort's slug-deterrent properties are due to compounds called saponins in its rhizomes and leaves. Shred some leaves, pour boiling water over them, give the resulting extract a good shake in sealed jam jar and you get this lovely frothy lather. Saponins are natural detergents, found in many plants including horse chestnut seed ('conkers'). A few years ago some Austrian research showed that slugs will not cross a barrier of ground-up conker seed meal and theoretically sprayed saponin extracts have the potential to protect seedlings that are susceptible to slug damage, but for the fact that saponins are very soluble and wash away in the rain.

Saponins are also present in quinoa Chenopodium quinoa seeds, a popular high protein grain with an excellent amino acid balance, sold in vegetarian and health food stores. They illustrate one of the great paradoxes of crop domestication, which often removes plants' natural defences and then must find alternative means for protecting crops from pests.

 

Quinoa is a very ancient crop from the Andes and the seeds need to be soaked in a couple of changes of water to remove the soluble saponins, which are mildly toxic to humans. Most quinoa seeds marketed for human consumption today should have been pre-washed but anyone growing it (quinoa can be cultivated in the UK - the above trial crop was photographed in Durham) should be careful to soak the seeds in at least two changes of water before consumption.  In the wild the bitter saponins are natural bird deterrents, so birds tend to leave those easily accessible, exposed seeds heads alone but attempts to breed more palatable saponing-free quinoa have produced crops that are rapidly devasted by birds. As is the case with many domesticated food crops, there is a conflict between breeding cultivars to remove anti-nutritional defensive compounds and protecting crops from pests. In order to make many crops edible for humans we need to weaken their natural chemical defenses and then must resort to alternative pesticides of one kind or another to combat the pests and diseases that inevitably attack: such is the treadmill of agriculture.   

Soapwort's saponins have been used for washing people and clothes for centuries. By all accounts an extract in hot water makes a fine shampoo, although I have to say that the extract smells like boiled cabbage so you'd need to rinse your hair very well afterwards and maybe scent the water with rosemary (as my grandmother used to do when she washed her hair). Soapwort extracts are also still used by conservators as gentle detergents to cleanse delicate fabrics and are reported to have been used to clean the Bayeaux tapestry.

You can read an interesting article about the origin of soaps, including saponins from soapwort here.

Punica granatum, Pomegranate

A ripe pomegranate fruit is a natural object of great beauty - as are its seeds, with their succulent juicy aril, when they are scattered like jewels over a salad. There are few fruits that have a richer store of mythology associated with them. In antiquity they were associated with fertility, due to their numerous seeds and the ease with which these germinate. It’s easy to grow pomegranate as an attractive conservatory plant by sowing a few seeds, then training the resulting plants on a single stem and shortening the shoots in the crown of the plant, to produce a compact head of foliage bearing attractive, waxy scarlet flowers – but usually no fruits in Britain.

Prof. Dr. Otto Wilhelm Thomé Flora von Deutschland, Österreich und der Schweiz, 1885, Gera, Germany

Image Source: Wikipedia Commons http://en.wikipedia.org/wiki/File:Illustration_Punica_granatum2.jpg

Pomegranate originates from northern Iran but by Roman times its popularity as a thirst-quenching fruit meant that it had spread around the Mediterranean. The Romans imported what they considered to be the finest fruits from Carthage, which they called Punica and which has provided the plant with its generic name. Pomegranates were widely grown in Roman villas and there are frescoes in the House of the Fruit Orchard in Pompeii dating from AD79 which depict the tree in fruit. According to Roman mythology, pomegranates are indirectly responsible for winter. In one version of the story Proserpina, daughter of Jupiter and Ceres (the goddess of the harvest), was abducted by Pluto and dragged into the underworld. In anger, Ceres froze the harvest and paced the earth, leaving desert wherever she travelled. Jupiter’s messenger Mercury eventually persuaded Pluto to let Proserpina go, but not before she had eaten six pomegranate seeds, the food of the dead, condemning her to live six months of the year with Pluto, during which time crops above withered in the winter, but when she returned to earth for the remaining six months she brought spring with her.

Dante Gabriel Rossetti. Prosperpine (1874). Tate Gallery London

Image source: Wikipedia http://en.wikipedia.org/wiki/File:Proserpine-(utdrag).jpg

By the 4th. century AD the fruit had acquired Christian symbolism, with the many seeds within the fruit representing the followers of the church. There is a wonderful mosaic from a Roman villa at Hinton St. Mary in Dorset depicting Christ flanked by two pomegranates, which by then had become symbols of Christian devotion. Catherine of Aragon, the first wife of Henry VIII adopted the pomegranate, with its crown-like shape, as her badge and the fruit features in historical and literary associations in Spain.

There is only one other species of pomegranate, P. protopunica, an endemic on the island of Socotra, and Punica is the only genus in the family Punicaceae.

Alocasia amazonica

Any plant with the specific name amazonica always has an air of the exotic about it, but the truth is that this attractive houseplant has no links with the Amazon or South America. Strangely, it's sometimes known as elephant's ears or African mask plant - and it has no links with Africa, either. It's a hybrid between two species from the other side of the planet, A. sanderiana from the Philippines and A. lowii from Borneo. I've no idea why it acquired the epithet amazonica. It makes a very striking houseplant , although once it blooms it tends to lose some of its symmetry. I always think that cowled inflorescence and ribbed, shield-shaped leaf give it an air of menace; it has a hint of voodoo or witchcraft about it, which I guess is where the name African mask plant originated.