The quince, like many fruit trees, puts out lots of branches that shoot skyward. It also likes shooting from the base -- its natural form is more a thicket than a tree. While quite picturesque, a tall thicket isn't easy to collect fruit from, so growers tend to prune to a vase shape. The vase shape allows air circulation through the middle of the tree, which reduces some diseases, and makes it easier to deal with the fruit. Quince trees should be pruned in autumn or winter, when they are dormant. I decided to wait until most of the leaves were gone from my tree before I started, last weekend.
I grew up with plum trees and feel confident to prune them, but quinces, being pome fruit like apples and pears, are a little trickier. They fruit on year-old spurs, which you have to be careful not to cut off. Fortunately, these spurs are quite distinctive. They are 10-15 cm long, somewhat flattened, and the tip is broader than the rest of the twig. You can see one in the photo of scale below, pointing to the right. Branches, of course, taper to the tip.
For the last few years, I have been (roughly) following pruning instructions from the Gardening Australia article about quinces. Here is my version of that pruning method:
- Plant your sapling. We'd do this in autumn to allow the tree to develop a good root system ahead of the summer heat. I'd prune it fairly hard, but not so hard that I can't tell whether it's survived!
- In late winter, prune to a single short trunk. While the orchardist in the article gives his trees a very short trunk, 60cm, he probably isn't picking up footballs, chickens or anything else from under his trees. I think 1m or more is a better trunk height for a tree in a home garden, but it depends a bit on your height and what you expect to be seeking under your tree, as well as how high you can reach to pick the fruit.
- There should be 3-5 healthy branches growing near the top of the trunk. Prune off all the rest, then shorten these framework branches to 50cm, with an outward-facing bud at the top of each. This should give the plant a Y-shape when you look at it from the side, and this is your vase shape.
- Don't cut off the stubby little fruiting spurs!
- Remove any diseased or dead wood.
- Remove all of the upright branches inside the vase at their base.
- Prune any side branches that have developed on the trunk or base of the tree.
- Remove any branches that cross others.
- Shorten the remaining branches to 50 cm.
That looks better, doesn't it? Though I feel I can take a bit more off, now I've had a good look at this picture -- I think the tree is starting to look splayed. Quinces are heavy fruit and a good crop (which is still unlikely on my tree, I fear) could cause branches to break.
This year, I've found I could remove an older framework branch as a new branch had grown in the exact spot I wanted. The older branch had zigzagged.
My tree has had another problem this year: scale, caught from the next door neighbour's fig tree. Scale are sap-sucking insects that live on the branches, and for protection cover themselves with a hard shell, which makes them look like limpets. They are farmed by ants for the honeydew they secrete, which also has the side-effect of feeding sooty mould. Neither the scale nor the mould have really affected the tree's production or health, as far as I can tell, but over time they would.
The commercial treatment for scale is White Oil, which is a petrochemical you use diluted. Mum tells me that her Dad used the washing water from the washing machine on his fruit trees. Probably any oil or soap will work, but here is my recipe, cut down from this one:
In a 500ml spray bottle, put 8ml vegetable oil and 2ml dish-washing liquid. Pour in 500ml water and shake to mix. Spray liberally on scale. The oil and detergent apparently smother the scale insect's breathing apparatus, and it's a useful recipe to try on any sap-sucking insect.