Pruning improves fruit production

Growing plums espalier-style.

It's that time of year to start thinking about pruning of roses and deciduous trees.
There are two main reasons for pruning a plant, firstly to improve its flowering and/or fruiting qualities. The second is to maintain a desired shape, either for improved visual appeal or for practical reasons.

The timing for pruning roses and many deciduous trees and fruits falls during the winter months when these plants are dormant. A guide for pruning stone fruit in particular is to do it on a day where warmth and air movement are such that you would be able to dry washing. Pruning on a damp, wet day significantly increases the risk of the spread and infection of bacterial and fungus disease. The use of pruning paste such as Grosafe Organic Prune n Paste or Yates Prune Tec on cut ends of branches is also important to minimise the risk of disease and insect invasions.
■ Rose pruning is essential to reinvigorate the plant, promoting new growth and subsequent flower development. July is the best time to prune roses in Whanganui gardens. If they are pruned any earlier they tend to sprout into new growth while the weather is still cold and there is then a higher risk of frost damage to the growth.
Many people struggle to know where to start when pruning. It is important to use the correct tools for pruning as too small a tool will make any job difficult. Secateurs for small twiggy growth, loppers for small branches and a pruning saw for larger branches.
The first step is to simply remove any dead, diseased and badly insect infested branches and then carry on from there. Where prunings are diseased it is important to burn the prunings, or send out with the rubbish rather than composting. Thin, weak stems should be removed with stronger ones retained. Inward facing and crossed branches should be removed also. The aim is to open the centre of the plant up to allow increased air flow which reduces insect and disease infestation in the coming season. The remaining branches should be reduced by up to three-quarters in the case of a bush or standard rose. Climbing roses should be pruned by approximately half and laterals shortened by two-thirds back towards a main leader.
■ Fruit tree pruning is primarily undertaken to allow sufficient light to penetrate into the canopy area to maximise fruit set, yield and fruit quality. Here are some pointers on pruning and training some fruits.

■ Almonds are usually pruned and shaped as vase shaped trees. Train the tree to 3-4 main limbs. Almonds fruit mainly on short spurs which bear for up to five years. Prune out about one-fifth of this wood each year. If numerous suckers arise in the centre of the tree, they can be removed in summer. Keep a strong sucker and allow it to grow if a replacement limb is required. Old but still healthy trees can be stimulated into good growth by heavy pruning.

■ Apples, pears and other pip fruit trees have been trained and pruned to various traditional systems for many years including; open centre/vase shape, central leader and espalier. Predominantly the central leader system is used.

■ Central Leader System.
With this system a single central vertical trunk is selected to support the fruiting branches. The branches radiate from the main trunk and form a Christmas tree type shape. This allows maximum sun to branches with the lowest branches being longest and then getting shorter higher up the trunk. Apples and pears produce flowers and fruit mainly on the two-year-old and older shoots and on short spurs produced on the older wood. Trees need a moderate prune during the winter to stimulate growth for next season's fruit and to maintain an open, well balanced structure of the tree so that they crop well, the fruit is of good quality and the tree's branches are strong enough to carry the weight of a heavy crop.

■ Open Centre/ Vase Form.
To train a tree in this way the centre leader must be removed and then encourage 3-5 major limbs to develop. This vase shape allows good air movement through the tree as well as good light on to the branches. This method of training is highly recommended for peach, apricot and nectarine trees.

■ Espalier.
For best results the wall or fence that is chosen should face north and receive at least six hours of sunshine each day. The tree needs to be trained from planting with unwanted branches removed depending on the shape you want to train your espalier to.
For some good videos on fruit tree pruning check out this link; www.waimeanurseries.co.nz/how-to-guide/category/fruit-tree-pruning-videos.
Research by experts has identified that the best flavoured and biggest fruit are produced in the largest quantities on branches that grow on an angle of between 30 degrees and 120 degrees from the vertical with the best branch angle being 30 degrees above the horizontal.

■ Apricots bear fruit on short spurs that form on the previous year's growth and on older spurs that can remain fruitful for up to 3-4 years. Pruning is aimed at maintaining the shape of the tree and removing any old unproductive wood. Prune and train an apricot tree to a vase shape. Protection of pruning cuts is necessary in apricots to prevent the entry of silver leaf and bacterial blast infections which can also attack plums and cherries. Use a pruning paste over all cuts to assist healing and help prevent infection. Summer pruning is often recommended to lessen the risk of silver leaf infection otherwise choose a day that is warm enough to get the washing dry! Not a dull, damp day when the incidence of infections will be increased.

■ Cherries fruit on spurs on two-year-old and older wood. Older trees should be pruned in summer to restrict vegetative growth and induce the formation of fruit buds. As a winter prune, spurs may be thinned or shortened and the branch leaders pruned to shorten replacement laterals to reduce the tree height. Upright or over vigorous growths should be removed or tied horizontally to balance tree growth as required. Note that the vigorous growth of cherries may be inhibited by growing them as a fan espalier. As for apricots, some summer pruning is recommended to lessen the risk of silver leaf and stone fruit blast infections. It is also advisable to construct a frame and cover it with bird netting to protect the fruit for your own benefit.

■ Peaches and nectarines bear fruit only on the shoots produced the previous year. Pruning is carried out to encourage new growth and replacement shoots to maintain a balanced and open branch framework in the tree. There are three different kinds of bud; plump fruit buds, small pointed growth buds and triple buds that have a plump central fruit bud with growth buds on either side. On branches where extension growth is required prune back to a growth bud or failing this to a triple bud.

Pruning and training fruit trees
Basically the objectives of good pruning are to;
1) Maintain the size and quantity of the fruit.
2) Remove dead and diseased wood.
3) Train the young tree so that it will develop a vigorous strong framework of branches able to carry heavy crops over a long period of time without damage to the branches of the tree.
4) Train the tree to a form (vase shape, central leader shape, etc), which aids the management of disease control and harvesting.
5) Provide good quality and an even distribution of healthy fruiting wood throughout the tree.
Note that every time a pruning cut is made plant growth is stopped in one direction and encouraged in another. Always make cuts back to or just above some growing point - a fruit bud or strong lateral (side branch) - or to a main branch.

■ Mark these free pruning demonstrations on your calendar;
All at Springvale Garden Centre, 18 Devon Rd, Wanganui.
Rose Talk & Pruning; Sunday, July 2 / repeated on Sunday, July 16, both at 2pm.
Fruit Tree Talk & Pruning Demonstration; Sunday, July 9 / repeated on Sunday, July 23, both at 2pm.

Gareth Carter is general manager of Springvale Garden Centre.