Golden Hop, Humulus lupulus aureus

Hops have been cultivated in Britain for flavouring beer since the sixteenth century – and for much longer in continental Europe – thanks to the resins produced at the base of the bracts in the female flowers (seen in the picture here), which are converted to bitter isohumulones during the brewing process. There are separate male and female hop plants but in modern times only female hops (with the cone-like flowers in the photo here) have been cultivated, as the seeds are undesirable in the brewing process.



My reason for growing hops (the golden-leaved variety) is rather more prosaic. Hops are rapid climbers with incredibly tough stems and for about a decade it was only the covering of hops woven around the fence posts that kept the fence at the bottom of our garden upright, after the posts had rotted at the base.


Charles Darwin was fascinated by climbing plants and during one of his bouts of (probably psychosomatic) illness took to his bed and had hops in pots brought into his bedroom, so he could wile away the hours studying the climbing process in this plant. He recorded his observations in detail in his book The Movements and Habits of Climbing Plants , published in 1875, in his usual precise prose.

“ When the shoot of a Hop (Humulus lupulus) rises from the ground," he wrote,"the two or three first-formed joints or internodes are straight and remain stationary; but the next- formed, whilst very young, may be seen to bend to one side and to travel slowly round towards all points of the compass, moving, like the hands of a watch, with the sun. The movement very soon acquires its full ordinary velocity. From seven observations made during August on shoots proceeding from a plant which had been cut down, and on another plant during April, the average rate during hot weather and during the day is 2 hrs. 8 m. for each revolution; and none of the revolutions varied much from this rate. The revolving movement continues as long as the plant continues to grow; but each separate internode, as it becomes old, ceases to move.”


Darwin was describing the process that botanists refer to as circumnutation, where the shoot tip describes a wide circle until it touches something that it can coil around (clockwise, in the case of hops). He went on to time the rotations of a hop shoot over no less than thirty seven rotations, testament to Darwin’s incredibly meticulous approach to making scientific observations that can, regrettably, make some of his books somewhat tedious to the modern reader. Still, the mental picture of Darwin laying in bed, carefully timing the rotations of hop shoot tips with his watch, does have a considerable charm.

You can find some further information on hop epidermal hairs used in climbing and also hop resin glands by clicking here.

Iris spp., Iridaceae

Until last year we had a large patch of this Iris unguicularis growing outside our back door, between the house wall and the path - a sunny, well drained, south-facing spot that suited it perfectly and guarateed plenty of flowers from Christmas onwards. This photo was taken in January last year, after a sleet shower, when the plant was blooming in the thawing snow. Soon after that I dug it up so that I could relay the path, and divided the plant, and there's no sign of flowers yet this year, which is a shame. It comes from North Africa.

You can appreciate the primrose fragrance if you bring the flowers indoors, although they only last for a day. Iris unguicularis (also known as Iris stylosa) is a delightfully delicate winter-flowering Iris but it was always hard to find blooms as perfect as this one to photograph. Snails hibernated in the dry leaves that accumulated at the base of the plant and often began to nibble the flowers even before they opened. The dry leaves were also favourite nest material for field mice.

Every year I plant pots of Iris danfordiae so that we can enjoy their vivid but short-lived flowers in the conservatory in late winter. Then I transfer them into the garden, when the bulbs produce numerous smaller bulbs that take years to reach maturity and only flower sporadically. I must have transplanted a couple of hundred into the garden, but never see more than a handful of flowers every year. It comes from Turkey.



When it comes to spring-flowering Irises, this is my personal favourite - Iris bucharica which comes from Central Asia, growing in high altitude areas of Afghanistan, for example. I have tried it outside in the garden a few times but it never thrives here, perhaps because the garden is too shady, but in pots it produces a fine display of beautifully fragrant blooms in March, and for my money it's a far superior container-grown Iris to the ubiquitous I. danfordiae.

Hydrangea spp., Hydrangeaceae

Season's Greetings and Best Wishes for 2011 to all readers of this blog.

I know some people who think that Hydrangea flowers are more attractive when dead that alive. It's a sentiment that I have some sympathy with...

... because I don't find the heavy, long-lasting infloresences of mop-headed Hydrangea macrophylla cultivars particularly attractive, but when winter has done its work on the dead flower heads the skeletonised florets, like those in the first photograph, are transformed into something rather delicate and beautiful.

Hydrangea infloresences are an interesting example of division of labour, where the central mass of short-lived fertile flowers, bearing stamens, stigmas and ovaries, have no particular visual advertising to attract insects but devolve that job to the large sterile florets, that surround the edge of the inflorescence like orbitting satellites. Petals wilt as soon as a flower is fertilised but since that outer ring of sterile advertising florets can never be fertilised they last indefinitely, throughout the whole flowering period and often right through the winter as skeletonised petals.






















The arrangement is delightful in some of the larger species like H. aspera (also known as H. villosa) when it's grown in an open, woodland garden.

Advertising all those fertile florets with just a handful of sterile florets is a very efficient way for the plant to attract its pollinators, but it's hardly surprising that plant breeders have hybridised and selected species for large numbers of sterile, long-lasting florets for maximum impact in a shrub border, reversing nature's economical use of advertising in the quest for maximum visual impact.

Tephrocactus articulatus var. papyracanthus, Paper-spined Cholla

This must surely be one of the most intimidating of all plants - the Paper-spined Cholla Tephrocactus articulatus var. papyracanthus. It comes from Argentina and those sabre-shaped spines that look so lethal are about eight centimetres long, but they're not as dangerous as they look. They really are like paper and simply bend under the slightest pressure; you'd be hard-put to draw blood with them. The tufts of tiny bristle-like hairs called glochids that you can see at their base are far more of a problem. They have barbed tips and are intensely irritating when they embed themselves in your fingers.The easiest way to remove them from flesh is to use a piece of adhesvive tape to pull them out.

Paper-spine cholla ( or the 'Edward Scissorhands' cactus, as my kids used to call it) is a slow-growing relative of the prickly pear cactus and is easily propagated by breaking off one of the jointed stem segments and rooting it in well-drained, gritty compost - but be sure to watch out for those nasty little glochids.

Clematis cirrhosa

My Clematis cirrhosa, whose straggly stems climb through a crab apple tree in my garden, managed to produce just this single flower before the first spell of freezing weather arrived. There are more well developed flower buds on it but the icy weather has returned and it's doubtful if they'll open now. Bearing in mind that this species hails from the Balearic Islands it's a small miracle that it survives here at all. It came through last winter safely so I'm optimistic that it'll do so again.

In milder parts of southern England there have been several reports of bumblebees that emerge on mild days in mid-winter visiting these flowers, along with Mahonia blossoms, but that's unlikely during this winter's icy blast.

Chinese lanterns,Physalis alkekengi var.franchettii

My grandmother in Sussex used to grow Chinese lanterns Physalis alkekengi var. franchettii to perfection, but I've always struggled to grow them up here in North-East England, not least because the slugs and snails zero in on them almost as soon as new shoots appear in spring. Looking at the natural distribution of the plant - southern Europe and eastwards across drier parts of Asia, it's not surprising that I haven't been able to grow these well. Gran's garden was mostly flint and chalk and she grew them in a sun-drenched spot in gravel at the base of a south-facing bay window, which provided a fair approximation of the Mediterranean climate and soils that this plant enjoys.

The orange papery 'lantern' is formed from the sepals (collectively the calyx) of the flower that inflates once it has been pollinated, enclosing the....

......shiny red berry within. The dried plant makes a colourful winter decoration but if you leave some outdoors the softer parts of that inflated calyx rot away surprisingly quickly, so that by Christmas you have ....

... only the skeleton of veins left which - with a light spray of gold laquer - makes a delightfully intricate Christmas tree decoration.

There seems to be some taxonomic uncertainty surrounding this plant, which is sometimes known simply as P. franchettii. According to the late Graham Stuart Thomas - a gardener who really knew his perennials - P. franchettii has more pointed lanterns - like those in the first photo above - compared with the rounder P.alkekengi, in the skeletonised example above but, since he also mentions that they hybridise, it's reasonable to conclude that they are merely varieties of the same species.

Madagascan Lace Plant, Aponogeton madagascariensis

I've never seen a living specimen of Madagascan lace plant Aponogeton madagascariensis but I found this pressed specimen in the herbarium of Durham University's School of Biological and Biomedical Sciences. I suspect it's a very old specimen as it still bears an old Latin name for the genus, Ouveranda. These look like skeleton leaves but in fact they are intact - during the final stages of development of the expanding leaves of this aquatic plant the cells between the veins die, during the process of programmed cell death (apoptosis) leaving a network of veins surrounded by living photosynthetic cells. The development of the leaf has recently been studied in great detail and you can read the scientific paper from the American Journal of Botany that describes the process (which also includes photos of the whole, living plant) by clicking here.

































In this close-up of a portion of the pressed leaf you can see the ladder-like arrangement of leaf veins that are surrounded by photosynthetic tissue. Apparently this plant is a popular but challenging species to grow for tropical aquarium enthusiasts and you can read an account of its cultivation here.