Of the more than 1,600 carnivorous plant species and hybrids so far identified, many are hard to obtain or difficult to grow. This chapter therefore concentrates on those plants which are most suitable for the beginner, all of them being easy to grow, inexpensive, readily available and fascinating or beautiful. (The compost types referred to at the end of the cultivation notes are described in table 3, p.13).
Perhaps the best known carnivorous plant is the Venus fly trap, Dionaea muscipula. This incredible little plant is often responsible for arousing interest in carnivorous plants as a group and yet has given rise to most of the misconceptions associated with them.
The sole representative of the genus, it comes from the Carolinas in eastern North America. The plant grows the green trap-bearing leaves, approximately 5 in. (12.5 cm) long, for most of the year, except in winter. The extraordinary trap mechanism consists of two slightly fleshy pads, hinged together at the end of the leaf, each with a series of fierce-looking but soft spines arranged round the edge, almost resembling eyelashes. The inner surface of the pad may be flushed pink or, in good specimens, an intense red and bears three small erect 'hairs', which act as triggers. As a precaution against accidental triggering of the trap by falling debris or rain, either two separate hairs must be touched or one must be touched twice; in addition, if these two movements do not occur within a specific time period of about 2 to 20 seconds, then the trap will remain open.
Once the trap is sprung, the leaf goes through several amazing changes. In the first stage, the pads bend in towards each other rapidly, so that the fringes of soft spines interlock. Any further action must be stimulated by the efforts of the victim to escape, as another protection against mistaken identity. If it is indeed an insect, the trap now enters the second stage and closes tight, suffocating or crushing it. This sealing of the trap is the result of cells growing on the outside of the pads - the fastest growth known in any plant. Enzymes are then emptied on to the prey, which is
Opposite: The Venus fly trap is famous for its dramatic trap action (see also p. 6). Note sundew at bottom of photograph
Striking Sarracenia leucophylla has a network of deep red veins on the complicated trap (see also p. 12)
slowly dissolved, nutrients are absorbed through the trap pads and a short burst of leaf production usually follows. Each trap can be re-used three or four times before it dies naturally and is replaced.
Dionaea produces insignificant white flowers in late spring, held high above the traps to enable insects to pollinate without being caught. Seed production can be copious, but should not affect the vigour of mature healthy plants.
A windowsill in direct sunlight is an excellent place for Dionaea, although it will survive happily in a cold greenhouse. Grow it in a half-pot and stand in a tray or saucer of soft water for most of the year to keep the compost wet. During winter, when Dionaea is dormant, keep the compost merely damp by watering occasionally. Some success has been recorded with plants outdoors, but if overwintered outside, they never grow to their best and will be killed in severe weather. Compost: A. Temperature: 50°F (10°C) winter minimum for best results.
Seed germinates easily on shredded sphagnum moss or pure perlite, preferably in a temperature of 70-80°F (21-26°C).
The pitcher plants of North America are probably the most popular of the carnivorous plants. Although only a handful of species exist, there are several subspecies or varieties of each and an almost bewildering choice of hybrids. They range in height from the prostrate forms barely a few inches tall, with horizontal pitchers sometimes 8 to 12 in. (20-30 cm) long, to the largest of the upright forms which can be a majestic 3 ft (1 m) high. Pitcher colours also vary, from light yellow through green to intense purple, often overlaid with splashes of deeper colour on the throat or veining. Perhaps the queen of this eye-catching genus is S. leucophylla; the lower part of the pitcher is green, which gradually fades to near or pure white at the top, with a network of deep red veins.
The flowers precede the pitchers from early spring to midsummer and deservedly attract attention. They are held proudly aloft at or above the normal full height of the pitchers and come in colours from cream through yellow to brick-red as well as gorgeous dusky pinks and oranges. When the four large petals fall, the central part of the flower, a massive umbrella-shaped style, is left in all its glory until middle or late summer. These flowers are also good for cutting or drying and, although a few have a slightly unpleasant odour, others have a delightful perfume. Pitcher production continues into late summer. Finally, some species develop strap-shaped winter leaves to take the plants through into spring.
The trap itself is a complicated structure and manages to catch its prey without movement. (Sarracenia are therefore passive traps, contrary to popular opinion.) At the pitcher head is a large fixed lid, which acts as a landing platform and is often marked with veins to lead flies down into the throat. It may also be generously supplied with nectar glands to attract the prey. Short hairs make it easier for the insect to maintain a foothold here but, as it descends, downward-pointing hairs decrease the opportunity for retreat. Further down into the trap, it will reach a more slippery area, where nectar is produced in abundance, and then well into the throat, a smooth wide band, which is capable of secreting digestive enzymes. On this slippery surface the fly will inevitably lose its footing and fall to the bottom of the pitcher, while the downward-pointing hairs on the walls prevent any
escape. At least the intoxicating nature of the nectar must make death quite painless.
Grow Sarracenia in good light, but avoid direct sunlight through glass, which can cause leaf burn. Use full-length pots for all except the prostrate plants and stand in a tray of soft water. In winter, however, the compost should be kept damp, not wet. Prolonged winter temperatures above 60°F (15°C) interrupt the normal period of dormancy and often result in poor specimens the following year. Compost: A. Temperature: 32°F (0°C) winter minimum; S. purpurea purpurea is hardy.
By rhizome cuttings of mature plants or from seed. Seeds may be presoaked to aid germination, which otherwise usually begins after about eight weeks but may take several years.
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