If you have available space in a greenhouse or conservatory you will quickly come to realise that this adds a valuable extra dimension to your fruit tree growing exploits. Not only are there a number of fruit trees that will appreciate the protection and warmer environment, that might be unsuitable for your garden space, you will also get the benefit of earlier crops too.Assuming that your available space is limited here we aim to explore options to get the maximum benefit of that available space as well as some basic tips on how to grow to get the best from them.
Fruit trees for the greenhouse
1. Growing in pots or the greenhouse bed or border
This the first point to consider. If the greenhouse is on a hard standing base then you may need to grow in containers; or you may wish to build a small raised bed in which to plant them. Such a raised area would need to be not less than 24-30” deep. It may seem easier just to grow in containers but planting either in the ground or into a raised bed does have benefits. The extra root run will make it easier to keep up with inevitable water and the extra root growing space will result in better growth. So if you were automatically assuming to grow in containers that may ben an option to explore.
When building a raised bed fill it with good quality top soil or a loam based compost. This has more heart and body than peat and coir based products which tend to become impoverished and lose water more quickly.
For container growing a standard size of around 20 litre capacity is ideal for most subjects. Type and dimension is less important as long as the overall capacity is there. Resist the urge to over-pot because not only does the substrate stagnate, you do need to remember to limit growth and this actually brings about better crops than trees which perhaps grow over vigorously at the expense of fruit.
Again a loam based compost such as John Innes number 3 should be used. This will have sufficient nutrients to get them growing well for the first few weeks. Thereafter a fortnightly foliar feed should be applied, or use osmocote granules which are slow release and will do the job for several months. Only feed whilst the trees are actively growing for it is a waste of time applying fertilizer when the trees are dormant or have stopped growing in early Autumn. Early Spring through to late Summer is the key time to give extra food.
Watering is of course vitally important. As a rule of thumb little and often is strongly recommended, early morning and late Evening. If you over do it or water irregularly this can result in fruits splitting. Try to get in to a routine of watering at the same time each day. Also remember to water at the base of the tree rather the top. Try to keep the foliage dry, for wet foliage is more likely to go down with disease.
2. Disease prevention
Is also vitally important for the closed atmosphere of a greenhouse can quickly become a breeding ground for undesirable insects and bacteria. Provide plenty of ventilation especially on hot days.
Avoid watering leaves by watering at the base of the trees. Keep the area as clean as you can removing detritus and fallen leaves as fastidiously as time allows. Avoiding overcrowding with judicious pruning also helps a great deal as the air circulation around the trees will increase and prevent the onset of disease.
As mentioned in one of our other articles on tips for growing healthy trees, making sure the trees are well cared for and growing as strongly as possible will also aid the prevention of trees because happy trees are healthy trees! This means regular watering, and feeding too.
3. Temperatures and growing environment for fruit trees
Very hot temperatures are to be avoided during the summer with shading of the roof and good ventilation. Your fruit trees may appreciate some warmth but remember they are not tropical and will get stressed if experiencing temperatures which are too hot. Under these conditions they may go in to what is termed early dormancy where they lose their leaves several weeks earlier than normal. Such trees will usually leaf up again in the Spring but it still isn’t a good thing.
Conversely during the winter, it might surprise you that you don’t really need to provide any extra heat whatsoever unless frosts are very penetrating. All of the subjects we will talk about shortly are well able to withstand a light frost so just be prepared to offer some light frost protection during the worst of the winter weather. Often times the added protection of the glasshouse or conservatory is sufficient to get them nicely through the winter without any added heat.
At no time should you provide heat during the winter that is likely to force them into early growth for this is undesirable. Although they will naturally leaf up earlier in the spring than outdoor subjects, you don’t want them starting into growth in the middle of the winter which can happen if temperatures are too warm. Most fruit trees actually need a dormant period of several weeks, without it their natural season is skewed and they become weak over time. Buds and branches actually need to ‘ripen’ in order to flower properly in the Spring.
4. Flowers and pollination
When grown outdoors the flowers are of course pollinated by bees and other pollinating insects but there are unlikely to be any flying in your greenhouse. So you need to fertilize the flowers yourself by going around the open blossoms with a soft brush which will transfer pollen from one to another and do the job for them.
5. What to grow and how to grow it
Here’s the really enjoyable part! The most delicious of all fruit trees are temptingly yours to try!
These delicious fruits can grow satisfactorily outside under good conditions but unless you happen to have a warm sheltered corner or sunny wall they may not do well and in some more Northerly locations they can be a waste of time because younger growths get frost damaged and die back and the blossoms invariably get caught by late frosts as these are very early to flower in the spring. Not so when growing in the greenhouse. Apricots are relatively free from disease, making them even better for greenhouse growing!
You have two ways of growing them under cover and consideration must be given to this because of course head room is going to be limited.
Fan training is a method whereby the tree is grown flat, usually against a fence or wall. But this can equally be done at the gable end of the greenhouse and support given by a bamboo framework. Such trees can be kept to a height of around 6’ which is just nicely within the scope of the average greenhouse. You will need a similar width for one tree. As fan training is itself a restrictive growing method it is quite easy to control a fan trained apricot and they are adaptable to allowing you to train to the available contours.
As far as varieties are concerned Goldcott is probably the best for yield and quality. It is a newer variety and very pleasing too. The old favourite ‘Moorpark’ also deserves mention and continues to do well with a lovely flavour. Alfred also has a very good yield and well worth growing.
If you don’t fancy fan training r have no suitable space for one the easiest option is to grow a small bush tree. As apricots are not compatible on small rootstocks they tend to be quite vigorous and unsuited to container growing as bush trees. But there is one naturally more compact variety ‘Isabelle’ so this is the one to go for. It’s easy to grow and reliable, performing really well in a greenhouse. It is less suited to fan training so keep it as a small bush tree.
Botanically almost the same and requiring the same conditions and cultivation. Again as for apricots they can be grown fan trained or as bush trees. Not possessing the same vigour as an apricot, even standard varieties are quite easily contained in a pot. One advantage of growing in a greenhouse is that they are less likely to get peach leaf curl or at least if they do it will be markedly less severe as the leaves will be predominantly dry and this limits the spread of the spores.
Peach and nectarine trees have really lovely comparatively large pink flowers and these are early to open even outdoors so in a greenhouse they can be showing colour by late February – a real joy and harbinger of Spring!
For peach trees Peregrine is the standby variety which usually does well. But although a standard variety it is certainly not lacking in flavour either, as it is a white fleshed peach and super-sweet. So all things considered this has to be first on the list when choosing which variety to grow. If you prefer a yellow fleshed peach then have a look at Duke of York; this old variety has a succulent flavour and red flushed fruits, it also usually ripens a little earlier than Peregrine. For something that comes a bit later try ‘Rochester’ which possesses a really rich flavour and plenty of colour to the skin. And lastly if you’re looking for something a bit different the speciality variety Kestrel is well worth a mention.
There are also truly miniature varieties Garden Lady and Bonanza. Top grafted on to a clear stem making a small neat tree, they only reach a very manageable 90-120cm’s. Yield and fruit quality isn’t so good as with standard varieties but they require little or no pruning and the fruit produced is still more than nice.
Nectarines - Lord Napier is the most popular and rightly so. White fleshed and sweet with a bold red flush. Humboldt is another worth mentioning with a really good flavour.
All peach and nectarine varieties are self fertile.
Although often grown in a greenhouse, Figs are pretty hardy outdoors as well. The main reason for growing them under cover is that the later fruits often fail to ripen properly outside unless the weather us favourable but this isn’t a problem with the added warmth of a greenhouse or conservatory. The fruits seem to take on an added succulence too! Plus they make really attractive plants with their large lobed leaves. They can be really vigorous so contain them in a pot rather than the greenhouse border. You will get more fruit that way as well.
Brown Turkey and Brunswick are the most familiar varieties with green-purple fruits and are good doers. White Marseilles has whitish green fruits and are even sweeter. Figs are self fertile and seldom get any disease.
You might not have thought of growing a cherry in the greenhouse but there are advantages. Commercially, cherries are nearly all cultivated under cover these days, gone are the days of the commercial large scale cherry orchard. This is because you get a much better crop of quality fruits. The blossom is prone to frost damage and the fruits are often taken by birds unless the trees are netted when grown outside.
Rather than growing the trees permanently inside I would recommend growing your cherry trees on the dwarfing Gisele 5 stock in a container and moving them in to the greenhouse just before the flowers open, keep them in until you have harvested the fruit then stand them outside again until the next Spring.
Good varieties are Sunburst with it’s rich dark fruits, Stella which is dark red and very flavourful and Regina which produces very good later fruits of good quality flavour and appearance – a favourite amongst commercial growers. Merton Glory is a white cherry so called because of the white inner flesh and pretty pinkish fruits – it is very sweet indeed.
Sunburst and Stella are self fertile, but Merton Glory and Regina will need another different tree to pollinate.
Remember only to grow on Gisele 5 dwarfing stock which is very manageable and perfect for container growing and can easily be kept to 180cm’s or a little less.