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Thursday, January 13, 2011

Butterwort, Pinguicula moranensis, Lentibulariaceae

Carnivorous plants have a problem. On the one hand, they must catch and digest insects to supplement the meagre soil nitrogen supplies in the boggy habitats that they inhabit. On the other hand, they depend on insects to pollinate their flowers, so there is no future in 'biting the hands that feed them' to the extend that they produce no seed. So most tend to have flowers that are well separated from their lethal, carnivorous leaves by a long flower stem - and this attractive butterwort from Mexico, Pinguicula moranensis, is no exception.
This species makes an excellent plant for the cool conservatory, for two reasons. One is that it produces these attractive magenta blooms from late autumn right through until early summer.

The second reason is that it's a formidable consumer of several annoying greenhouse pests, including whitefly, greenfly and those annoying little mushroom gnats that tend to come with many brands of today's potting composts. The way in which small insects are attracted to the glutinous glands on the leaves and are then trapped and digested is very satisying - and you can see some examples of butterwort's insect catching prowess here. This plant is flowering flypaper.
This species is very easy plant to propagate - just pull the leaves away from the leaf rosette and insert each to a depth of about 5mm. in a moist compost. Buds will develop at each leaf base, to produce a new rosette, much as they do when you propagate an African violet or Streptocarpus species.
Place butterworts amongst your conservatory plants and they will act as a form of botanical biological insect control; they won't eliminate your pest problems but they will produce tangible evidence that they are making inroads into the insect pest population. This plant comes with a feelgood factor if you are troubled by tiny winged insect pests.
Seen from the side, it's clear that this butterwort's flowers must be pollinated by long-tongued butterflies, landing in the flat-faced flower and probing with a long proboscis to the bottom of that long nectar spur behind the flower. The flower is the only part of the plant without adhsive and digestive glands - look closely at the flower stalk (double-click) and you can see here that it's coated with adhesive glands that have caught a few tiny greenfly.

Thursday, January 6, 2011

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.

Tuesday, January 4, 2011

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.