When it comes to growing fruit under glass, while tomatoes and strawberries might be about as far as many gardeners choose to go, these are certainly not the only possible options available. Even in the unheated greenhouse, a range of fruits, including grapes, peaches and lemons, can all be raised in surprisingly undemanding ways.
Many people are under the impression that growing vines invariably calls for high temperatures, but with a bit of care selecting the right variety, it is perfectly possible to have your own crop of grapes. Varieties such as “Black Hamburgh” or “Buckland Sweetwater” are ideal for cooler growing conditions and of course, there are many options open to the owner of a heated greenhouse.
Vines require open, free-draining soil to flourish and it is important to get this aspect of their cultivation right since water-logged soils can affect them quite badly. Young plants will need supporting as they become established – stout canes being the usual choice – the new spring growths being trained to the support as they develop. Vines produce their flowers and then their fruit on each year’s new growth, so to promote a good crop; the side-shoots produced in the summer should be pruned in the following winter, cutting them back to their last bud – a method known as “spur” pruning.
The plants will need some attention over the year to keep them in peak condition and must be watered thoroughly to ensure that sufficient water reaches all of the roots and fed with a good quality fertiliser. As the fruits develop, they need to be thinned to allow each grape the space it needs to grow to a good size – an operation usually carried out with long scissors with pointed ends, working upwards from the bottom of the bunch and removing the smaller ones.
Unfortunately, vines suffer from a number of pests, including aphids, red spider mites and scale insects, so a careful look out needs to be kept – and prompt action taken – at the first sign of trouble. The fruits can also be prone to mildew. With care and a little effort, however, even the smallest greenhouse can provide a few bunches of home-grown grapes.
Peaches and Nectarines
Both peaches and nectarines can be grown in either unheated or cool greenhouses. As with vines, selecting the right variety plays a big part in successful fruit production. The peach “Peregrine” is an ideal candidate, usually starting to ripen in August and has the advantage of being self fertile; “Hale’s Early” by contrast, although an excellent choice, needs another variety close by if pollination is to be successful. Amongst the nectarines, “Humboldt” and “Pine Apple” are highly suitable for the cool or unheated greenhouse, ripening later in the season, producing fruits in September and often into October.
Maintaining these trees in good health does demand a little time and effort, but in the long run, they can certainly repay it. Unlike vines, the fruit is produced on the previous year’s wood and it is usual to prune and train the tree to maintain a fan shape which provides ample room for the fruits to develop and makes picking them easier.
Peaches and nectarines grown in the greenhouse tend to have rather compact roots and as a result need to be watered frequently during the growing season and fed once the tree has become established. Given the absence of pollinating insects in the greenhouse, the plants need some help – the usual method being to transfer pollen from flower to flower with a small, fine brush. This needs to be done every day throughout their flowering, since not all of the pollen ripens at the same time – and to give the best chance of success, the humidity of the greenhouse should also be raised. When the fruits subsequently develop, it may sometimes be necessary to thin them. This job should be done when the fruits are about the size of walnuts, thinning out to leave around two fruits to develop per foot of branch.
Perhaps a little surprisingly, lemons, oranges and tangerines can all be grown in the greenhouse. They only need a temperature of around 13 degrees C (55 degrees F) for the pips to germinate and will survive the winter happily, provided their surroundings stay above 4 degrees C (40 degrees F). Although growing them from pips is the easiest way to produce your own tree, it is not exactly a swift process, taking anything up to ten years for them to begin producing fruit of their own. If faster propagation appeals, taking suitable cuttings should allow fruiting plants to be produced considerably faster.
Growing fruit in the greenhouse is not without its problems. Getting the conditions just right, avoiding the ravages of pests and disease – even raising the plants properly – all require a bit of effort to achieve, but in the long run, there is not much to beat being able to stroll out to the garden and pick your very own.