Gareth Carter: Pruning deciduous fruit trees and roses

Winter is a good time to prune trees into shape. Photo / 123rf

July is the time to be undertaking winter pruning. Trees are pruned for many reasons. Often they are practical reasons of how they impact on our lives, such as to ensure a tree is not blocking light into a home, or a branch may be protruding over a driveway or constantly dropping leaves into the spouting that one decides they can no longer want to clean it out.

For fruit trees, pruning is important to maximise fruit production and ease of harvest. For plants like roses, pruning is to maintain a compact bushy plant with a strong flowering display. If left unpruned they tend to quickly become scraggly in growth and sparse in their floral display.

Image / Supplied

The timing for pruning roses and many deciduous trees and fruits is best completed during the winter months when these plants are dormant and deciduous (have lost their leaves). The timing of pruning is part of the success, as well as making the right cuts.

In Whanganui, deciduous fruit trees such as apples and pears, along with roses, are best pruned during the month of July. Any earlier and in our temperate climate we risk getting a warm snap that makes the plant think it's spring. The plant can then produce some new growth which risks getting walloped with a July frost.

Pruning is best undertaken on a day you hang your washing outside. Pruning on a warm day is not only more pleasant, but significantly decreases the risk and spread of bacterial and fungus disease.

It is important to ensure the cuts that are made are "clean" angled so to not allow water to pool on the cut. I highly recommend the use of a pruning paste such as Grosafe Organic Prune n Paste or Yates Prune Tec to seal the cut ends of branches as this will minimise the risk of disease and insect invasions, which shorten the life of a tree.

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Rose pruning is essential to reinvigorate the plant, promoting new growth and subsequent flower development. 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. Use 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 and 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 about half. Laterals should be shortened by two thirds back towards a main leader.

For a good video giving a visual demonstration on rose pruning check out: www.springvalegardencentre.co.nz/gardening-info/rose-pruning/

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 5 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. Predominately 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 trees 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 onto 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 6 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.

Image / Supplied

For a good video on creating an espalier check out: www.springvalegardencentre.co.nz/gardening-info/espaliering-fruit-trees-video/

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; the best branch angle is 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 three to four 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.

Apricots and other stone fruit are best not pruned now but left until summer. This will lessen the risk of silver leaf infection.

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. Summer pruning is recommended to lessen the risk of silver leaf infection.

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 it will develop a vigorous strong framework of branches that is 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.

For a good video on winter fruit tree pruning check out: www.springvalegardencentre.co.nz/gardening-info/winter-pruning-fruit-trees-video/

There are also live pruning demonstrations that can be attended at Springvale Garden Centre, 18 Devon Rd, Whanganui.

Pruning pip fruit trees masterclass: 2pm, Saturday July 2.

Maximise soft fruit crops and pruning masterclass: 2pm, Saturday July 16.

For more gardening information visit www.springvalegardencentre.co.nz

• Gareth Carter is general manager of Springvale Garden Centre.