By Ray Goddard

Reproduced from Volume 7 of the Journal of the Carnivorous Plant Society. First published Spring 1983.

Many C.P. species can be grown in greenhouses or indoors, often at some expense. However, a lot of other species can be grown quite happily outdoors. The easiest way to do this is to grow them in pots, but this has two main drawbacks. The first is that a large group of plants can present problems for watering and can also look untidy. The other, as I discovered to my dismay, is attack by our winged friends. I left a pot of Sarracenia psittacina outside, and leaves and new growths gradually disappeared until netting was placed over it.

A relatively inexpensive method of solving all these problems and maybe more, is the following. Essentially, a wooden tray about 8” deep is built. A good size is 4’ by 5’, but this is adjustable to suit the number of plants and the space available. This is then lined with a plastic pool-liner. A large hole is then cut down to about 3″ from the top, which prevents flooding, as there is otherwise no drainage. The pool-liner can then be stapled down. Uprights are erected at the corners, and crossbars join them, to form frames on each side. (These sides should be 3’ to 4’ tall).

Next, the base is filled. For this, roughly the bottom 3” are filled with ‘tray gravel’ — available at garden centres — and is smoothed off. A peat/ Bedford (50/50) sand mixture is added up to the top of the plastic, and well-watered. When this has settled, the plants are planted in and the whole can be covered in sphagnum moss. The compost, and rest of the soil can be kept from the drainage hole using pieces of broken tile. Then the sides are filled in using a clear plastic or glass (glass is advisable, as plastic tends to need replacing every few years). At least one ‘door’ must be built into the sides, or else access to the plants is difficult. Design of these doors, and indeed details of the whole construction, I leave to the reader’s ingenuity, as different designs are better for different situations — eg. pets or the weather. Mine is on a flat roof, and built against a wall.

Plants

So much for the construction, what about the plants? Quite a good selection of plants are suitable for growing outside. I have found that Sarracenia flava, purpurea, x catesbaei, x melanorhoda and Darlingtonia californica thrive outdoors, and have done well, even over the winter 1981-82. Sarracenia leucophylla was planted out last summer, and seems happy but it has not been out long enough to tell definitely. A number of Droseras grow outside. All the ‘native’ ones (anglica, intermedia, rotundifolia, x obovata) do very well, as do Drosera filiformis and Drosera binata. All these plants grow quite happily, and about the only ones, I have found, that require particular attention are the Pinguiculas. P. grandiflora and vulgaris require shading from bright, direct sunlight. This can be achieved by placing roofing tiles or small sheets of hardboard on the sides, near the Pinguiculas. In order not to unduly shade other plants, all the shade-loving plants can be placed in one corner. Dionaea muscipula can also be grown well outdoors. The only real effect that not being in a greenhouse has is to produce slightly smaller plants, though these can look better than large ones. All of these plants can be arranged in any way, either scattered or in groups. Personally, I prefer them scattered, although some Pinguiculas and Droseras tend to develop into colonies after a while.

In this way, a large collection of plants only requires very little tending — watering and weeding mainly, but also the removal of dead growth after the winter. With our weather, during the spring to autumn, rain normally does all the watering. Even if it has not rained for a few days, the large water-holding capacity of the base ensures that it will not dry out. When the sphagnum moss is established, it acts as a good indicatpr to watering — when it dries out, more water is needed.

I find that the best way to water is using a large capacity sprayer such as the ‘Killaspray 4’, with collected rainwater. During the winter, watering is usually not required if a removable glass or plastic top is fitted. If a sloping one is fitted, not only is heat retained during the winter and moisture kept in, but any snow falling is kept off the plants. In the spring the top can be removed, and the plants will be found to be in good condition. If the top were kept on permanently, I am sure ‘greenhouse’ plants could be kept ‘outside’ all year round (one would, in fact, have a mini-greenhouse). I did say that this method solves some problems associated with pots. Watering is much easier this way, and if arranged well can look good. Also, for some reason, the glass sides prevent the birds from getting in, and no netting is needed. However, greenfly can be a slight problem, and brushing them off may be better than using chemical insecticides. This is because chemicals would remain in the bottom, and not get washed out.

The above deals with most types of outdoor plants, except Utricularia, U. vulgaris grows in a large fish tank. This can be by putting a good layer of peat on the bottom, and covering this with a layer of a heavy sand. The tank is then filled with rainwater and some pond water is added. When this has all settled, the Utricularia can be introduced. It is best to shade these as for Pinguicula – shade from bright, direct sun. I have found that black paint on the sun facing sides, and some wood over the top is effective in this. Some, like U. sandersonii, can be grown in large coffee jars, substituting the jar for the pot. If this is kept well-watered with a loose lid on it can stand outside, although it does like some shade. It should also be brought in during the winter. Many other plants, like Drosera capensis can be stood outside during the summer, but will need to be brought in over the winter.

This article briefly describes the methods I employ to grow C.P.’s outdoors, and I would be grateful to hear of any other species which could be suitable for growing outdoors.