Using the Sub-Stage Area in the Greenhouse
The area under the greenhouse staging can be a very useful place for growing plants — provided it is not already being used to house garden oddments. Just how useful depends largely on the greenhouse design, but with a little planning most of these often-neglected areas can be made very productive.
Never be tempted to use the space under the staging in your greenhouse as a gardening ‘glory hole’. Keep some clean bins, bags of compost, clean pots or boxes there by all means, but remember that dirty rubbish will harbour pests and diseases and make cleaning the greenhouse a tedious business.
Plants grown under the staging should not be set directly on the greenhouse floor. Cover the ground with plastic sheeting covered, in turn, with a layer of gravel or coarse sand; alternatively, place the pots on a slatted or mesh stage raised a few centimetres above the ground. This will prevent the plant roots from entering the, and also keep soil pests or worms from getting into the holes.
Use common sense when positioning your plants; put those needing most light at the back in the case of a glass-to-ground house, and at the front when the greenhouse has a base wall.
Undoubtedly the area under the staging is most versatile in a glass-to-ground greenhouse since it will receive plenty of light. The more light that penetrates the better, since a wider range of plants can then be accommodated. In the Dutch-light type of house, with slightly sloping sides, there is specially good illumination and plants set well back will get almost as much light as plants on the staging top. In all cases light can be increased by using slatted or mesh-topped staging. Some overhead light then usually finds its way through.
Try to prevent plant debris like dead leaves, fadedand drips from watering from falling off the plants on the staging onto the plants below; water or organic material left lying on plant foliage for any length of time can cause brown markings or instigate rot and fungoid growth. One way of avoiding this is to stand potted plants in plastic trays that have a layer of coarse gravel in the bottom; space the trays apart to let light through.
In the case of the base wall type of house the under-stage area will probably be very gloomy. This means you will have to be more selective in what you put there, but for some plants shade can be an advantage — even vital. In a few cases no light at all is wanted, for instance when blanching and forcing vegetables like chicory, rhubarb and endive. For these the area will have to be deliberately blacked out with black polythene. Where there is little light and not enough space to make the area useful for more ordinary plants, you can always grow mushrooms. These do not need light (though there is no need to black out completely) and they are easy to grow in containers filled with special compost that has been spawned by the supplier. Full growing instructions are issued with the containers.
Where light is extremely poor, very many ferns will thrive and can be used simply to give decoration to what would otherwise be an uninteresting spot, or to supply cut fronds for floral decoration, or as pot ferns for the house. What type of ferns you can grow depends on the temperature of the greenhouse. It is possible to buyof selected varieties of hardy, half-hardy and tender ferns in separate packets, to get initial stock.
If the greenhouse is a warm one or, at least, has a congenial temperature in winter, many exceedingly beautiful and colourful foliage plants of a sub-tropical nature will live happily under the staging in their natural jungle habitat they would enjoy considerable shade. Suitable plants include maranta (prayer plant), calathea, ctenanthe, foliage begonias, peperomia, Fittonia argyroneura and Dieffenbachia pieta all have exotically marked and coloured leaves.
Plants of the GESNERIACEAE family enjoy shade, and most of them have charming foliage and delightful flowers. These include streptocarpus (Cape primrose), sinningia (gloxinia), saintpaulia (African violet), smithiantha (temple bells), achimenes and Rechsteineria leucotricha.
Raising the temperature
You can raise the temperature of the area under the staging easily and cheaply, especially when the greenhouse has a base wall that will help retain warmth. In some cases the space can be ‘boxed’ or ‘cased’ with glass or plastic so that temperatures can be elevated quite considerably. The simplest method of heating is to use soil-warming cables.
In a glass-to-ground house useful early salad crops can be raised in soil-warmed beds under the staging — lettuce, beet, radish, carrot and numerous sprouting vegetables including mustard and cress. Later in the year these warmed beds can be used for starting tubers — like dahlias, begonias, sinningia (gloxinia), canna and the like — into growth and also for seed germination. Propagators can be sited under the staging where the shade will be an advantage for most forms of seed germination and for establishing cuttings.
Where there is little or no warmth, the area can be employed for storing dormant plants over the winter and for keeping overwintering storage organs or roots such as dahlias, summer-flowering greenhouse bulbs, chrysanthemum stools and the roots of tender garden plants. Most storage organs are best kept in boxes of clean sand or peat, but many roots have to be prevented from drying out completely during winter and you should make sure you have easy access to them for regular inspection. Some designs of greenhouse have ground-level vents allowing the under-stage area to be reached from the outside. This can be useful for cultivating salad crops.
Growing-on pot plants
Much of the general growing-on of pot plants can be done under the staging. Popular pot plants like cineraria, calceolaria, primula, polyanthus, cyclamen, coleus and ornamental capsicum can be housed there from the seedling stage to the size when they can be put into their final pots. For many of these plants the diffused light of the under-stage area is a great advantage and even when you move them to the top of the staging for display the glass will need to be shaded. The under-stage area is particularly useful to these plants when they are being grown on during the summer months. Most house plants, too, do not demand full light and can be raised from seed or cuttings under the staging for later removal to the house. Established house plants can also be given a holiday under the staging from time to time — they will appreciate the humidity.
Raising bedding plants
In the glass-to-ground house the under-stage area is invaluable in late winter to(January to March) when it is time to raise bedding plants and your greenhouse tends to become very overcrowded. As well as the initial germination of bedding plants, the trays and boxes can be kept under the staging for a time until the seedlings are well established. Take care, however, that the area is not too gloomy or the seedlings may become weak and spindly. The idea is to protect the seedlings from sunlight rather than to cast them into deep shade.