This is probably one of the most important ways you can extend your season for fruits, and vegetables. The original idea goes back to Victorian times when it was noticed that crops housed under cover were far more infested with pests and diseases than outdoor versions. And secondly that hardy productive fruits such as peaches and grapes often failed to thrive in permanently warm conditions. It was eventually realized that many crops physiologically demanded a minimum dormancy, in the region of a couple of months, of actual cold. Just pouring in more heat did not fix the problem, they had to be given some form of winter.

Orangeries, the first cover, were merely slightly less dim and frost free rooms which could house plants over winter but really were pretty unsatisfactory. Fully glazed glasshouses became possible, and hot flue then hot water and steam heating became available. If you had the cash you could have several; each suited to a different crop such as one for tomatoes, another for pineapples, melons, figs, peaches and grape and so on. For each crop prefers differing night and day temperatures and humidity and the latter need winter dormancy to thrive. That is easy, you turn off the boiler and open the vents for two months, the grapes chill and are happy. Of course if you had but one humble glasshouse in which you housed everything you couldn’t chill the grapes and peaches without killing the pineapples.

It was a prolific nurseryman, Thomas Rivers, from Sawbridgeworth that came up with the concept of the orchard house. In this one structure many different fruits could be brought to perfection by moving the plants in and out in pots and tubs as they required it. Rivers had already a lot of experience of growing fruit in containers and this was an obvious extension.

Of course with the earlier structures the plan was simple; move tenderer plants in tubs under cover and out again when the weather warms up again. Growing plants permanently under cover had then given rise to the problems mentioned initially- so far only solved by having dedicated houses for each. Some even tried to get round these problems by making the glasshouse dismantleable or movable on tracks to expose those with hardier contents to the weather. Then Rivers conceived we could grow hardy plants in tubs outside much of the time, getting rid of their burden of pests and diseases, and getting a winter chill. And then move them under cover to force them into early growth, protect the blooms from frost or rain, and or protect the fruits from birds. Thus the cover could be little more than as he put it, exaggeratedly, a glass roofed shed.

The house needs to be well ventilated in hot weather but can be totally unheated though naturally one will be much more valuable if it can be kept just frost free, however great heat is not required. The method relies solely on the difference in warmth to push dormant plants into earlier growth as soon are they are brought under cover. (Most can be fooled into growth though not all will crop- it was soon found that though most fruits could be tricked not strawberries- these were measuring not the warmth but the day length and proved difficult to fool, and indeed still are, though rumours of day length neutral varieties from the USA abound. It is still hard to get strawberries to crop much out of season though they can be brought on a few weeks early to great advantage.)

An Orchard house can be made from a polythene tunnel, a greenhouse, or even a sun room or conservatory will do if it can be ventilated well enough. Not only is great heat not needed it will cook and poach leaves and fruits. Ventilation is crucial. Large doors, good paths and easy access all round are essential as large numbers of heavy tubs (five gallon drums or thereabouts at least) have to be moved. Good standing such as concrete slabs stop roots finding their way into the ground. Plenty of water, preferably in butts inside so as at room temperature needs providing, and as it’s used on pots then best to be rain water to stop salts accumulating in the compost. Watering trays are dangerous as they can rot roots so quickly if the plants stand in them too long.

The system is of greatest use for those crops that experience the greatest difficulties grown continuously indoors or out. Peaches suffer badly from adverse weather outdoors and badly from pests within making them one of the most valuable. Pot grown peaches can still carry a couple of dozen fine large fruits yet take up only a square metre of floor space. Their move indoors, preferably before the buds start to open, can be from mid till late winter. Then they flower very early, possibly needing hand pollination, and crop in May and June, months before outdoor crops. They avoid the frosts on their flowers, peach leaf curl disease is prevented as the buds are kept dry and if ripened under cover the birds are kept off. By July the plants go back outside for the next six months. And Nectarines are even more worthwhile -requiring warmer conditions than peaches these rarely do outdoors but crop well by the Orchard House method.

Apricots are another fruit well worth bringing in from mid winter on as again the flowers avoid the frosts and their crop becomes almost certain. These are a most difficult tree to keep cropping and subject to water-logging rather easily but otherwise are easy. Cherries seem to resent the confinement in pots more by dieing a bit quick but effectively crop better than outdoors though only the sweet are worth it as the Morellos do anyway, even on a North wall. Cherries are so difficult to get otherwise as weather and birds conspire against the cherry grower. And keeping cherry trees in tubs really does keep them dwarf. I’ve treated plums, apples and a pear similarly but these seem a less useful return for the effort though a choice variety may be considered. Gooseberries have turned out a surprise favourite; forced by bringing their pots in in February they crop in May well before most other fruits and are well appreciated- indeed they are better than the outdoor ones.

The fruit most suited of all to orchard house culture is the grapevine. Planted in the ground these make huge growth, require major pruning regularly and give massive crops. If you have the right variety that is. Few are suited to cropping outdoors in the UK for dessert in most places. Most varieties will crop in some years, and a few crop well with good sweet grapes fairly often such as Boskoop Glory and Siegerrebe. But put them in tubs, move them in from mid-winter until early spring and you can be eating grapes in June and cropping almost any variety by August, even the old tasty varieties for hothouses such as Black Hamburgh. As soon as cropped the vines are pruned back ruthlessly hard and bunged outdoors again. Believe it or not they love it and most crop well each year. About four or five bunches per vine which again takes about a square metre. Thus you can easily fit nine different vines in the space otherwise occupied by one vine planted in the ground or border.

Of course not all plants of any variety need be brought in at the same time. Thus one variety can be made to crop over three or four times as long a season. By bringing another vine of say Boskoop Glory indoors every few weeks from mid winter until mid spring each can be brought to fruit sequentially from June till the outdoor crop ripens in late September.

And you can use the summer space created as they vacate. Sweet potatoes, chilli peppers and watermelons use the space made as cropped plants go out for their recovery in mid summer, and the first two crop more as they grow well on into autumn if frost free. Indeed the only sensible way to grow and store sweet potatoes is under cover in big tubs or bags, and to dry them off intact for winter use without disturbance. And several other crops can also benefit from the autumn use of an orchard house. Celery and leeks grown in containers can be brought under cover and kept growing longer and more tenderly than if left outdoors. Potatoes sown from midsummer can be cropped in big tubs- they give new potatoes for winter feasts but have to be under cover or the blight will get them before the cold most years. And of course all manner of herbs and salads can be sown or potted up in containers in late summer then brought under cover before the frosts damage them.

I find using my tunnel as an orchard house doubles up well with it over-wintering my citrus. True it gets a bit crowded until the citrus go out in May but then there is space for the next couple of months of cropping, when the sweet potatoes and so on use the space until winter. Then it all starts again.