Zwetschgen and plums are considered rewarding, and so they are. But a common frustration can be almost entirely avoided with the right pruning: brown, mouldy fruit that rots on the tree. The key is an open crown that air and sun move through.
This article shows you how to plant a Zwetschge or plum correctly and prune it over the years so it stays healthy and bears well. Which fruit suits you at all is settled first in Zwetschge, plum, mirabelle and greengage: who is who.
Planting: sunny and airy
Zwetschgen and plums want sun and a deep, non-waterlogged soil. Unlike the pear they are fairly undemanding about the spot, but an airy position matters more to them than a particularly warm one. Plant bare-root in the dormant season, with the graft union above the soil. The basics are in Planting a fruit tree: bare-root in autumn.
Many varieties such as the 'Hauszwetschge' are self-fertile and bear alone. Others reward a pollinator nearby with markedly more fruit.
Why the crown must stay open
The greatest threat to Zwetschge and plum is brown rot. The fungus enters through wounds and flowers and turns ripe fruit brown and mouldy on the tree. It loves moisture and still air in dense crowns.
Your most effective weapon is therefore not a spray but the pruning: an open crown, in which the leaves dry quickly after rain, removes the fungus's foothold. Part of that is consistently removing infected fruit mummies. More on this in Brown rot: brown, mouldy fruit.
How to prune correctly
Not in deep winter
Stone fruit responds to winter pruning with gummosis, the oozing of sticky resin at the wounds. Prune in mild, dry weather, ideally right after harvest in late summer or in late spring.
Build the framework
On a young tree, choose three or four well-spaced leading branches and a central leader. Anything too steep, too low or growing inward comes off. That creates a stable, open crown.
Thin out rather than shorten
On plums it is mainly about thinning. Take out whole surplus branches at the base rather than shortening many shoots. That keeps the crown airy without provoking wild regrowth.
Deflect the steep
Redirect steeply rising shoots onto flatter side branches. Flatly led branches bear better and break out less often under the load of ripe fruit.
Rejuvenate old trees gently
Do not free a long-neglected tree all at once, but over two to three years. A radical cut only triggers a forest of water shoots and much gummosis.
Keep it open, do not prune in winter, rejuvenate gently with age. An airy crown is half the harvest and the best prevention against brown rot.
The core rule for plum pruning
Frequently asked questions
When do you prune Zwetschgen and plums?
Not in deep winter, but in mild, dry weather, ideally right after harvest in late summer or in late spring. The wounds heal well then and gummosis stays minor.
Why do my Zwetschgen turn brown and rotten on the tree?
That is usually brown rot. It spreads in dense, damp crowns. An airy crown through thinning and the thorough removal of infected fruit mummies are the most effective remedies.
Do I have to prune plums every year?
An annual, light thinning cut keeps the crown healthy and the tree in shape. More important than the amount is the openness: better a little every year than radically every few years.
What is gummosis and how do I avoid it?
The oozing of sticky, glassy resin at wounds and bark damage, typical of stressed stone fruit. You prevent it by pruning in mild weather, working cleanly and not injuring the tree in deep winter.
Can I save an old, neglected plum tree?
Yes, but with patience. Thin gradually over two to three years instead of removing everything at once. That keeps the tree calm and stops it forming masses of water shoots.
