It is still not widely known among gardeners that some carnivorous plants are perfectly hardy and tolerant of even severe winters. In fact, all the three most popular groups have representatives which are hardy to one degree or another (see table 4, p.17), requiring habitats varying from bogs to standing water.
For perfect conditions, a boggy area or pond is needed. Those gardeners who already have a natural site merely have to choose which plants to grow. Otherwise, an artificial bog or pond should be constructed. To do this, first mark out the chosen area, preferably with a length of garden hose, which is easier to work with than other materials. Most ponds and bogs benefit from a surround of stone slabs, so allow for this too. Remove soil and any turf within the marked area to a depth of 12 to 18 in. (30-45 cm), ensuring that the bottom is level and that the sides are cut at an angle of about 45°, to prevent them collapsing. For a bog this single excavation is sufficient. For a pond, mark out another area within the hole, leaving a margin of at least 12 in. (30 cm) width. Dig out this area again in the same way.
Next, check that there are no large stones in the hole. To protect the liner from future damage by hidden stones, put a 1-in. (2.5 cm) layer of any available sand over the flat surfaces. For the stone slab surround, remove turf and soil to the required depth from the perimeter and then add a layer of sand. A pond liner, several varieties of which are available from garden centres, must now be fitted. To calculate the size of liner required, use the maximum dimensions of the pond or bog and the following formula: [length + twice maximum depth] x [width + twice maximum depth]. For example, if the pond is 10 ft long and 8 ft wide, with a maximum depth of 2 ft, the liner would measure: [10 + (2 x 2)] x [8 + (2 x 2)] =14x12 ft.
To fit the liner, place it over the hole and secure it at the corners with stones. Pour soft water into the centre until the liner is weighed down and remove the stones to allow the liner to settle on the sand. To produce a pond, continue to fill the remaining space with more soft water. For a bog, cut a £-in. (3 mm) drainage hole at a depth of 6 in. (15 cm) in the middle of each long side of the liner. Then almost fill the bog with a well mixed combination of damp or wet moss peat and washed sharp sand, approximately
5 parts moss peat to one part sand. (Sand can be omitted but helps the water penetrate the mixture.) Saturate the bog with soft water before adding the top layer, a 2-in. (5 cm) deep mixture of washed sharp sand, wet moss peat and live chopped sphagnum moss. This final layer should then be well watered, again using soft water. The bog or pond can now be completed by covering the edge of the pond liner with stone to form a surround.
Incidentally, a bog garden is an excellent alternative to an ordinary pond kept full of water, which poses a hazard to young children. It is also far more attractive than the common replacement for the pond - a sand pit. The artificial bog is still an unusual feature in gardens, but it allows experimentation with a new range of plants.
Carnivorous plants should not be exposed to the risk of burning by wind and midday sun. However, sensible planting of other bog-loving plants will provide shelter, while adding to the natural look of the bog. These could include medium-sized plants such as the flag iris, Iris kaemp/eri, and marsh marigold, Caltha palustris (for further recommendations, see the Wisley Handbook, Water Gardens). It is also a good idea to group the carnivorous plants together, interspersed with other plants which are better at binding the soil with their roots. Otherwise, birds will find the damp soil an irresistible attraction and spend many glorious hours uprooting the plants in their search for grubs, worms and other food. For small areas, an efficient but unsightly alternative is to cover the bog in chicken wire mesh or net, which can be supported on a frame or short stakes above the surface. If preferred, the wire can be laid on or just below the surface and holes cut for the initial planting. Although the wire will eventually rot, the area will by then have a good covering of moss and most plants will be well enough established to withstand the assaults of birds.
Planting in the bog is simply a question of digging a small hole and inserting the rather small root system of the plant. As the soil is wet, no watering in will be required. In a pond the plants can be grown in pots, which are placed in the water in the same way as with other aquatic or marginal plants. Remember that the acid water of such a pond is not suitable for fish.
Only the hardiest carnivorous plants will survive the winter in or under water, although many will do so in the bog garden. These can be moved to the pond between spring and autumn or planted permanently in the bog. Sarracenia, for example, can be grown with the crowns either submerged or exposed and will accept temporary flooding lasting as much as several months. The pond is ideal for L/tricularia, providing a permanent home for the hardy species; U. australis will even tolerate some lime. (See table 5).
Table 5; outdoor habitats suitable for hardy carnivorous plants
Scree (very well drained)
Pond margin Pond (true aquatics)
Pinguicula grandi/Iora (lime-tolerant) Drosera peltata
Sarracenia purpurea purpurea, S.flava; Drosera rotundi/olia, D. anglica, D.filiformis filiformis; Pinguicula grandi/lora, P. vulgaris all hardy plants suitable for bogs, especially Pinguicula grandi/lora
L/tricularia vulgaris, U. australis, U. intermedia, U. minor
Although many of the true alpines among carnivorous plants are rare, there are a few more readily available species which should succeed in a rock garden or scree.
There is often a natural hollow at the foot of the slope of a rock garden, which acts as a sump, draining the surrounding land, and as a consequence is always damp. Some of the alpine Pinguicula, especially P. grandiflora, are invaluable for such a spot and beautiful even without their attractive flowers.
On a really well drained scree slope the tuberous sundew, Drosera peltata, is well worth a trial. The soil should be almost pure gravel or grit mixed with only a small proportion of moss peat. The plant will need shelter from wind and will not want to be cold and wet, particularly in winter, so a cover may be required. It should do well in a situation which suits Soldanella. However, prolonged cold spells in wet conditions will damage the tubers and it is advisable to keep some spare plants indoors or under glass.
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