I attended a brief workshop at Garden of St Erth in Blackwood to find out more about summer pruning and how to improve our efforts at the garden. Here’s a summary of what I picked up from the day, as well as a few images (click on the image to see the full photo and hover your mouse for the caption)….
The best time to prune is in summer, unless you are carrying out major structural cuts/changes (needing to use a pruning saw or anything bigger than secateurs), and in the first three or four years of the tree’s life when you are developing a structural framework for the tree, looking at how it is growing and forming, and choosing branches that will become fruit bearing. After that, it should all be done in summer. For stonefruit, all pruning should be done in summer, regardless.
Winter pruning is an English hangover; in Australia’s hot summers plants will shut down a bit and we don’t get true winter dormancy like Europe does anyway. Winter pruning shocks the tree and then it will respond and grow back even more vigourously, in the same place. Summer pruning tricks the tree into thinking it’s older, so it will provide fruit sooner. The tree will also heal more quickly, since sap is flowing well. Constant winter pruning will make the tree think it is perpetually juvenile, so it will keep producing lush, vegetative growth, indefinitley.
Summer pruning is especially good for espaliering.
The more dwarfing your treestock, the less pruning is needed, dwarfing stock are also very suited to espaliering.
Pruning hygiene is vital – regularly sharpen your secateurs (and use a small sharpening stone or file as you prune) and clean them in metho after you use them and also in between each tree, so you don’t spread disease around your garden. This is critical for stonefruit where gumosis or bacterial canker can easily spread (esp cherries). Use a sealant for any big cuts, to protect from disease.
When tying espalier branches to wires, use soft ties or pantyhose and tie them loosely. Check the ties are not cutting into the tree as it grows. Once a branch is tied down for a whole season or so, it can be released – branches shouldn’t need tying down permanently.
There are two ways that trees form fruit:
permanent fruiting spurs (most apples, pears, plums, almonds, apricots, cherries) – the spurs are fatter than other buds and flowers and fruit will grow on the same spot every year
tip fruiting (peaches, nectarines, olives, a couple of heritage varieties of apples, inc. Bramley) – a new tip/spur will grow at the end of a branch each season and then die back after fruiting, in the same way as berries.
The permanent fruiting spurs tend to form on the undersides of branches, or horizontally along the branch. Any upward growth tends towards vegetative, leafy growth which is what you prune. When you cut this verticle growth, leave 3 to 5 buds at the base of the main stem, to encourage budding lower down on the branch that could become a new fruiting spur.
Tip fruiting trees will produce flowers and fruit on one year old wood and then die back, so if you are not sure what to prune, wait until they fruit and die back and then cut only the dead branches, again leaving 2 or 3 buds for new growth to emerge. With tip fruiting trees you can also cut back the length of the branches and they will fruit further back along the branch (one way of keeping trees to a manageble picking height and size). The apple exceptions – eg. Bramley apples, are best grown as an open tree – not espaliered because of their tip fruiting form – and then remove any branches in winter, do some tip pruning in summer- but don’t overdo it because you will remove potential fruit!
The rule of thumb is:
horizontal growth = fruit, verticle growth = leaves/branches
Only make a cut if you know why you are doing it and what the intended result will be. Don’t make cuts without intent and understanding why you are making that decision to prune that branch or growth.
It is hard to bring an espaliered tree back to something manageable if it has been let go for a few years; the best way is to start off properly and then systematically prune each year to end up with the desired form. There are many espalier shapes. Woodbridge Fruit Trees in Tassie have good guides (and fruit!). Vigorous trees such as citrus, peach, plum and nectarine tend to be trained as fan shapes as they grow more profusely than say, a dwarf apple, and citrus can be trained against a north facing brick wall. Tip fruiting trees can also be trained in a Spanish Bush form.
You can prune more than once over summer, eg. in small amounts from December through to March, rather than a one-off. But late February is a good time if you are pruning once.
Whilst they are fruiting, trees need a good supply of water, the equivalent of 50mm a rain each week, but don’t need as much other times because you want to encourage deep rooting (and don’t over-fertilise either – a handful of potash, dynamic lifter/compost in late winter should be enough, plus seaweed and wormjuice in spring).
Pruning espaliers and other forms is all about cutting off verticle growth. The more vigorous the verticle growth, the harder you prune, but leave about 3 -5 buds at the base of branch, to give the lower ones a chance to form permanent fruiting spurs on those forms.
Thinning fruit is important if you have a lot of fruiting spurs or a lot of fruit from the one bud. Usually there will be a cluster of 4 – 5 fruit and one will be much larger – termed the “king fruit” – and that is the one you should thin. Leaving this fruit on will cause all of the other smaller fruit to drop off, leaving you with one huge fruit – pretty impractical for a family! Better to take the large fruit off and let the others develop to uniform size.
If you have very long new growth, bend the branch towards the ground using twine and this will encourage the formation of more fruiting spurs (horisontal growth) along its length.
If your tree is too far-gone, lost its shape and form, or has been left for a few seasons and is unable to be renovated – it may be better to start over by cutting the tree back by a third and trying to re-establish a framework again, in winter. Then carry on with your summer pruning.