Give plants a warm and sunny disposition when you grow under glass to extend the season
Whether you call them orangeries, hothouses, greenhouses, conservatories or glasshouses, structures that allow you to control the environment have been around for centuries. Since Roman times people have been discovering ways to harness sunlight to grow crops from other regions or out of season. However, it wasn’t until the 16th century that glasshouses appeared in Britain, designed to nurture the vast quantities of exotic plants that were being brought back by explorers, plant hunters and travellers.
Prior to the mid-19th century, a glasshouse was an object of awe as only the wealthy could afford the expense of glass. The Victorians popularised their use with the fashion for cultivating exotic plants in the golden age of gardening. An emergence of new wealth from the industrial revolution and an expanding empire, plus the repeal of the glass tax in 1845 and the window tax in 1851 reducing the cost, manufacturers began producing functional versions responding to the demand and social changes.
Technical advances contributed as well. Designs became lighter, less ornate, specific to use and varied in sizes, including cultivation of exotic and ornamental plants, display houses, ferneries, vineries, cut flower houses, potting sheds, hot houses, cold frames, and conservatories. They also featured in kitchen gardens, allowing exotic crops to be grown, due to the development of cast iron and coal fired heating.
Ever wondered what the difference is between a greenhouse and a glasshouse? There isn’t really. The greenhouse became a general term for glasshouse in the 1830’s, as a smaller scale comprehensive place for growing, rather than a range of glass, hot and stove houses.
Today the theory remains largely the same, just with more modern climate control and lighting systems. Ask yourself the important question – what do you want a greenhouse for? To propagate, to grow tender ornamental and productive plants, to display a collection, overwintering, or even to include a living space – these are all considerations to inform your choice.
Location, style and material then come into play, as does whether you want to heat it or not, and finally, of course there’s your budget. Even the smallest unheated greenhouse allows you to extend the seasons and grow a range of crops and ornamentals as it will be warmer than outside, while heating your greenhouse will extend the growing season further and allow you to grow tropical and sub-tropical plants as well as over wintering tender plants. Normally aiming to keep the glasshouse frost-free at around 5 degrees is standard unless growing really exotic plants.
Here in Hampshire, we haven’t got far to go for advice on the options available. ‘We use folding benches a lot as it gives the option of the benching for propagation space February to early June and then floor space for over wintering plants,’ comments Paul Smith, technical director for Ropley-based Griffin Glasshouses, that specialize in bespoke modern and Victorian designs.
An advantage of growing under glass is growing a wider range of edibles from seeds, nurturing their progress in controlled conditions, and also supplying fresh produce through winter.
‘November is a great time to plant and harvest some microgreens. Microgreens are essentially small versions of the mature plant that are cut as soon as they develop their first pair of leaves that look like the adult plant. They are nutritious and intensely flavoured and can be harvested with scissors just as you would with cress, in as little as a week. Re-sow regularly to keep supplies topped up all through the winter months. Some varieties to try are beetroot, broad beans, coriander, radishes, peas, rocket and chard,’ suggests Nelly Hall, brand director of Petersfield-based aluminium greenhouse company, Alitex.
Award-winning landscape and Garden designer Adam Vetere grows a range of tasty crops, such as unusual tomatoes, aubergines and cucumbers, in his attractive glasshouse, which takes centre stage in his potager at Old Camps in Headley and also overwinters tender specimens.
‘I like to overwinter some of my citrus trees under glass as this will allow them to continue their cycle of flowering and fruiting without them going into a dormant state when the temperature drops too low. By doing this it allows the trees to flower and develop mature fruits. I also take in some of my aloes, aeoniums and agaves, especially if it is a very cold winter,’ he explains.
Finally don’t worry if you haven’t the room or the budget for a full-scale greenhouse there are many alternatives on offer, from mini-greenhouses, cold frames, polytunnels, to cloches. You may have space for a smaller lean-to structure that benefits from the residual heat stored in the wall during the day. A cold frame, which is simply a wooden or brick box with a sloping lid of glass or polycarbonate, may be ideal for your needs. Frames and mini greenhouses are useful to wean greenhouse plants to the outdoor conditions, and a cloche is helpful to protect seedlings in spring in the kitchen garden or weather sensitive plants through winter, being a portable microclimate.
You can also use your windowsills; windowsill propagators are available and plants such as cacti and succulents will be just as happy and don’t take up much space in your home.
Did you know?
Around 30 AD it is believed that the ailing Emperor Tiberius was prescribed by his physicians to eat one cucumber a day and as the plant only grew in summer his skilled gardeners developed a heated specularium, with stone walls for insulation and translucent sheets of mica to let the sunlight in, to supply them. According to Pliny the Elder, once the means of growing were established, ‘he was never without’.
Get the look
Position your greenhouse where it will receive good light levels year-round, is sheltered from winds and close to a tap and power point.
Avoid extremes of weather as that can damage plants so it’s important to have a thermometer and check it regularly.
Adjust ventilation to maintain temperature and prevent fungal infections.
Watering is key as plants can dry out quickly.
Divide your glasshouse into zones, such as a place for propagation, one for growing on, and a section for plants that will permanently live in the glasshouse. This will allow you to meet the plants needs better and make life easier in the long run.
Get in touch
Griffin Glasshouses, Ropley, SO24 9SQ
Bespoke greenhouses, glasshouses and orangeries
griffinglasshouses.com
Alitex, Petersfield, GU31 5RG
Home of the modern Victorian greenhouse, range of National Trust greenhouses
alitex.co.uk
Adam Vetere Landscape and Garden Design
Old Camps, Headley, RG19 8LG
adamvetere.co.uk
