It has often been said that one of the best things about a greenhouse is the range of plants that it allows you to grow. While many of the usual contenders for bench space are old familiars the opportunities available for growing under glass need not be limited to cultivating “traditional” greenhouse plants such as tomatoes, begonias, bromeliads and the like. The best greenhouses – like the best gardens – reflect something of the interests and personalities of the gardeners. With a little bit of care and imagination, it is possible to grow some surprisingly unusual plants under glass.
Alpines in a Greenhouse?
Alpines must seem one of the strangest candidates for the greenhouse. The idea of a plant designed for survival at high altitudes – clinging on between the upper limit of tree-growth and the permanent snow line – being molly-coddled in a greenhouse does appear a bit bizarre – at least on first sight. However, although their chosen home is certainly an extreme environment, the worst of the British weather can still pose them a few challenges – not from the cold, but from the rain and distinctly changeable conditions of a typical UK winter.
In their natural habitat, they are hidden beneath a blanket of snow for many months of the year, which keeps them at a fairly constant cool temperature – though several degrees warmer than the air above. Most importantly, it keeps them dry until the snow melts in the spring. Mimicking these conditions over-winter in an unheated greenhouse, with a well-drained and low-nutrient soil, should give them the perfect head start for the new growing season and have them in peak condition for planting out later in the year.
Water Under Glass
For the avid water gardener, winter often signals a long wait until early summer warms the pond and aquatic plants can start growing again. However, building a water garden in the greenhouse or conservatory is not particularly difficult to do and even if it is unheated, both the range of plants you can grow and the length of growing season becomes greatly extended. Provide a little heat and the possibilities really begin to open up, allowing specialist plants, such as the more exotic types of water lilies, to thrive and flower – though they do need a fairly constant temperature around 27 degrees C (80 degrees F) and heated water. Many other more traditional greenhouse exotics will also benefit from the additional humidity this kind of indoor water feature will provide, especially bromeliads, pitcher-plants and “air” plants such as Spanish Moss, making it possible to create your own little bit of jungle to help offset the worst of the winter blues. Alternatively, if the idea of bringing a tropical swamp into your greenhouse does not appeal, hardier water lilies – such as the many varieties of Nymphaea – fit the bill well, some kinds needing only three or fours direct sunlight to flower.
Even if you have no wish to grow aquatic plants in your greenhouse full-time, if you have an outdoor pond, a small water feature can help bring-on native species a little sooner than they would otherwise be ready and can be invaluable in over-wintering less hardy species. Plants such as the Water Hyacinth and Water Lettuce, for instance, are sold in their hundreds each summer in garden centres and aquatic shops but seldom survive to the following year left to the rigours of the British climate. Removed to even the most modest indoor pond, however, both will happily sit out the winter and be raring to go when the weather warms up sufficiently, giving you an early display and saving you a small fortune in new plants.
South Africa’s living stones – their botanical name, Lithops, literally meaning “stone-like” – must have one of the best claims to being the most unusual of plants. Perfectly adapted to mimic the rocks and pebbles in which they naturally grow, they are all but indistinguishable from them until autumn when they produce white, yellow or pink, daisy-like flowers. Although all of the species are roughly similar in size – most being only an inch or so tall – they display such an extensive variety of patterns and colours that collecting the different forms of these extremely slow growing plants has come to be something of a minor hobby.
Each plant actually consists of a pair of very fleshy leaves which are fused together to give a squat stem-like body, with a slit at the top. The size of this slit depends on the species, ranging from a small indentation to a split running almost down to soil-level. Like the alpines they can survive periods of cold and need to be kept dry in winter, making them ideal candidates for cultivation under glass.
For many gardeners there are few things better than being able to experiment or simply indulge an interest that otherwise you might not be able to do and having a greenhouse can open up all sorts of opportunities to do just that. What you grow really is up to you and is probably only really limited by the type of environment you can create, the amount of hard-earned cash you want to invest and your own imagination. If nothing else, growing something a little unusual certainly gives any greenhouse another point of interest.