Growing Fruit Plants in Pots in the Greenhouse

 

Pots are a very good way of growing many kinds of tree fruit where space in the garden is limited but, of course, they have other advantages as well. Apples, pears, plums, cherries, peaches, nectarines, apricots and even grapes and figs can all be grown successfully in pots.

We have already seen a few of the benefits, but it would be as well to look at them now as a whole rather than piecemeal. The obvious one is that growing fruit in this way takes up virtually no room at all. This has clear benefits in small gardens, but it is also useful in larger ones because it allows you to grow a lot more kinds and varieties of fruit. You can even look upon it as a trial ground for something that you fancy, but would like to know more about before committing yourself to larger quantities.

The mobility of the trees is an enormous advantage; it allows them to be moved to different places. If this sounds rather pointless, don’t forget that it is really the whole object of the exercise: the ability to move the trees under cover at times of the year when the weather is likely to damage them. The important time is in the spring when the trees can be brought into the greenhouse if a night frost threatens to destroy the blossom and new growth. Another time that protection is usually needed is in the autumn when gales are liable to bring off the ripening fruits.

By the same token, if you have a fruit cage, the pots can be moved in there when the fruit is ripening to protect them from birds and children.

On top of all this, there is what might be called the ‘show-off, factor. If a tree in blossom or carrying fruit is placed in a suitably ostentatious position, it will undoubtedly cause raised eyebrows and will be the talking point of the neighbourhood.

 

Management

Despite all the advantages of this form of fruit culture, there are obviously problems, the main one being that trees in pots require quite a bit of attention during the summer In addition, the smaller trees are clearly going to produce smaller crops than trees in the open ground. A problem that arises here is that, to produce a small tree in a pot, logic says that it should be on a dwarfing rootstock. Wrong. If a fruit tree on a dwarfing rootstock is planted in a pot, it will be dead in a few years.Why? Because a fruit tree on a dwarfing rootstock needs very good growing conditions to survive and thrive. In a pot, the growing conditions are far from good. In other words, a fruit tree in a pot is kept dwarf by the restrictions of the pot, not by the rootstock. So, under the restricted conditions already imposed by the pot, the tree needs a strong rootstock to survive.

Although it is of lesser importance, it is also wise to consider the choice of varieties in connection with their own vigour as well. Some are naturally stronger growing and may need a more dwarfing rootstock than others.

Because a much smaller tree is going to be grown, we must choose a suitable shape for it and it is generally accepted that the dwarf pyramid shape serves the purpose well. The main exceptions to this are peaches and nectarines which do better as open-centre bush trees. Figs are also different and should be fan-trained to a cane frame.

If you can, start with a two or three-year-old tree that has already been pruned to the basic shape; this means that it will at least start life by pointing in the right direction.

The pot, or other container, in which you are going to grow the trees should certainly not be too large. Don’t be misled into thinking that, because you are dealing

with a tree, the container has to be the size of a water butt. The pot size to start with is usually a 10in (25cm) one. It can progress over the years to a 12in (30cm) and 14in (35cm), but never start too large or the tree will put on too much growth and will not fruit for some time. All containers must have drainage holes.

We have already looked at the choice between clay and plastic containers and have come down on the side of clay for the sake of its stability; it also looks more the part. However, if you feel like breaking away from a true pot and going in for a more decorative container, modern moulded plastic troughs etc. are excellent, provided that you choose a good, thick one. Again, don’t forget the drainage holes.

We have also touched on suitable composts and have come out in favour of John Innes Potting No. 3, but do make sure that it is a good make and that it comes from a reputable source; there are still some cheap brands about which are no good.

 

Potting Up

Now all is ready for potting up the trees. The container-grown trees available from garden centres today make life a lot easier as they already have a restricted root system so, in this respect, they are better than bare-rooted ones. Added to that, they can be potted up at any time of the year and not just in the winter, as with bare-rooted specimens.

When potting, the first thing to do is to put crocks over the drainage holes. This is followed by a ½-1in (1.25-2.5cm)of coarse peat siftings, on top of which goes the first layer of potting compost. Containerised trees can then be put straight into the pot, after removing the container; and compost firmed down the sides. Plant it so that the tree is about an inch deeper than it was previously. Leave about an inch of exposed rim at the top for watering. Give the whole thing a good soaking and the job is done.

Planting bare-rooted trees is carried out in just the same way except that, after the first few handfuls of compost have been returned, fidget the tree about so that the compost falls down between all the roots. Firm the compost down as you go. As a rule, repotting or potting on will only be needed every other year.

 

Feeding

Feeding is easy enough, but it does need regular attention during the growing season. With newly potted trees, the fertiliser in the compost will last about a month, but, soon after fruit-set in the spring, a dressing of a balanced feed, like ‘Growmore’, should be given. If the leaves turn pale in the summer, it means that the tree is hungry, but, instead of piling on more ‘Growmore’, change to fortnightly liquid feeding. This is quicker acting and you have more control over growth. Nowdays you can buy pellets or capsules of fertiliser that last a whole season. These are great and they really do work. Take your pick.

 

Pruning

Because most kinds of tree fruits are going to be grown as dwarf pyramids, the greater part of the pruning will be done during the summer and not in the winter.

To form a dwarf pyramid after winter planting, if you are starting with a dormant one-year-old (maiden) tree, cut the central stem back to 20in (50cm) high. All side-shoots longer than 6in (15cm) are then shortened to 5in (13cm). Shorter ones are left alone. In the following winter, the new growth on the central leader is cut back to 8 – 10in (20-25cm) and the new growth on laterals (side-shoots) to 6-8in (15-20cm). From then on, winter pruning is confined to shortening back the central leader as before; side-shoots are dealt with in the summer as follows.

In late July or early August, when the growth has stopped, the leading shoots on the branches (branch leaders) are shortened to 5-6in (13-15cm). Side-shoots arising directly from the branches are cut back to 3in (8cm) and those from previously pruned side-shoots to 1in (2-3cm).

This routine is carried out every winter and summer until the tree reaches the desired height, after which the central leader is treated as a side-shoot.

 

Overwintering

All hardy fruits must be overwintered outdoors with the pots plunged in peat, sand or straw to stop them getting frosted and possibly broken. It also protects the root-ball from any intense cold. An alternative is to bury the pots in a trench in a spare piece of ground but there may be the problem of worms entering the compost in the pots through the drainage holes. The whole point about leaving the plants outside during the winter is that they need a certain amount of low temperature treatment in order to fruit properly. If you keep them in the greenhouse over the winter to be kind’, you will simply reduce their fruiting capacity. Most are perfectly hardy and need the cold to operate properly,

In fact, fruit trees should only be brought into the greenhouse when it is going to benefit them; at other times they should be in a sheltered and sunny position outside. The time for housing them will, of course, vary with the kind of fruit. The really hardy types, such as apples, pears, plums and cherries, should only come under cover at the times already mentioned. Grapes, figs and peaches etc., the slightly less hardy fruits, can also benefit from greenhouse conditions when the fruit is ripening towards the end of the summer At this time, they need all the sun and warmth they can get to ripen and mature properly so that their full flavour is developed.

Having said that, it is a good idea to bring the trees in at night when in blossom to protect them from any frost and also on wet and miserable days. This, though, raises the question of pollination.

 

Pollination

Obviously a few bees and insects are going to find their way into the greenhouse, but there are seldom enough to guarantee effective pollination if the weather is poor for days on end. Most trees will need to be hand pollinated.

There is nothing difficult about this as it merely involves transferring pollen from the male anthers of the flowers to the female stigma. This is achieved very simply with an artist’s soft paintbrush. You still see some writers recommending a rabbit’s tail instead of a brush, but this is only a relic of a bygone age; a soft brush is perfectly adequate and does an excellent job. Choose a warm and sunny day for the hand pollination; you will find that more pollen is released then.

Keep the trees under cover for a few days after the petals have fallen to make sure that fertilisation has taken place, then they can be moved outside again.

 

Rootstocks

Mention has already been made about the different rootstocks on which certain tree fruits are grown and how these will affect the vigour and ultimate size of the trees. There are, therefore, definite rootstocks which are favoured for pot culture.

A short list of the most suitable rootstocks for the different kinds of fruit, together with some of the best varieties might, therefore, be helpful:

Apples – Rootstocks M26 and MM106. Cookers are on the whole less suitable than dessert varieties because of their usually greater vigour, but Lane’s Prince Albert (cooker) is naturally dwarf and spreading.

 

'Concorde' PearsPears – Rootstock Quince C if available, Quince A if not.

Louise Bonne is particularly good for its quality and Concorde for its reliability.

 

Plums – Rootstock Pixy.

Early Transparent gage, Reine Claude de Bavay and Denniston’s Superb are all top quality desserts, but grow Victoria for its reliability if you want to play safe.

 

Cherries – Rootstock Colt.

Stella is a reliable self-fertile variety so is the best choice for gardens.

 

Peaches — Rootstock St Julien A.

Peregrine is the hardiest variety and suitable for outdoors. Royal George is a good late variety that should be ripened under cover if the summer is poor.

 

Nectarines – Rootstock St Julien A. Grow Lord Napier Apricots – Rootstock St Julien A.

Moorpark is the traditional variety, but there are two from Canada: Farmingdale and Alfred.

 

'Brown Turkey' FigsFigs – Grown in their own roots.

Brown Turkey is the standard variety, but Negro Largo is higher quality though definitely needs a greenhouse.

 

Grapes — Grown on their own roots.

Black Hamburgh and Muscat of Alexandria (white) should both be grown in the greenhouse, though Hamburgh will succeed outside on a warm wall in the south.

14. May 2011 by admin
Categories: Fruit Gardening, Greenhouse Gardening | Tags: , , , | Comments Off on Growing Fruit Plants in Pots in the Greenhouse

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