How to prune Opal plum trees?

TL;DR

Opal is compact (2-3 metres), self-fertile and early-ripening. Prune May-September (summer only), form an open goblet, maintain central leader. Opal grows slowly and compact, so less aggressive pruning than Victoria. Remove water shoots yearly. No winter pruning - canker risk. Opal fruits by year two and yields small but excellent black plums.

Opal: small but mighty

Opal is a relatively new plum variety (1980s introduction) that is perfect for small gardens. Unlike Victoria, Opal grows much more compact - typically 2-3 metres tall, only 2 metres wide. Opal also ripens earlier (August-September) and is far less disease-prone.

The pruning approach is therefore different. Opal needs less invasive pruning because it does not outgrow itself. But light attention still prevents dense interior and water shoot issues.

Why Opal prunes differently than Victoria

Victoria: grows explosively, produces many water shoots, needs heavy yearly pruning.

Opal: grows steadily, water shoots rare, light yearly pruning suffices. Opal wants "maintenance" not "reconstruction."

This means: if you want a compact tree without yearly heavy work, Opal is your pick.

Shaping: goblet form for small spaces

Opal grows naturally compact, so you need no intensive forming.

Year 1: Set the tree with central leader at 40-50 centimetres. Let four side shoots become scaffolds (toward four compass points). Remove everything else.

Year 2: Give each scaffold one side branch, cut to strong eye. Lightly thin the interior: remove anything drooping or touching neighbours.

Year 3+: Maintenance pruning. Remove water shoots, thin dense wood, prune damaged branches. Done.

Summer pruning: May to September

This is essential for Opal.

May-June: Check for water shoots. Opal rarely gets them, but if it does, remove immediately at the base.

June-July: Side branches longer than 30 centimetres: cut back to six leaves. This prevents Opal getting wild in summer.

August-September: Light hand. Remove only obvious problems. Opal is already fruiting - be careful not to knock off too many.

October-April: No pruning. Canker risk.

Fruit thinning

Opal fruits early in year two. The fruit is small (30-40 grammes), so thin less aggressively than Victoria.

June-July: Thin to one plum per 8-10 centimetres of branch. Opal needs more fruit to be economically viable. Heavy thinning enlarges them, but cuts total kilogrammes.

Practical: Leave more fruit than on Victoria, but remove obvious doubles and damaged.

Water shoots: rare but possible

Opal grows steadily, so water shoots are scarce. But if they appear:

Treatment: Remove at the base or gently snap while green. Once hardened: saw close to the trunk.

Water shoots on Opal often signal stress (drought, damage) - check soil conditions if you see many.

Canker: prevention beats cure

Plum canker is rare on Opal (far less prone than Victoria), but possible.

Prevention: Summer pruning only, no winter wounds. Disinfect shears. Remove debris.

Treatment: See indrawn, dry patches? Cut back to clean wood, at least 10 centimetres below visible damage. Very rarely recurring on Opal.

Opal plum pruning step-by-step plan

Step 1: Timing check

May-September? Yes? Proceed. October-April? Wait until May.

Step 2: Inspection

Circle the tree. Water shoots? Dense interior? Deadwood? Damaged branches?

Step 3: Remove water shoots

Remove all water shoots at base or low on trunk.

Step 4: Open interior

Remove anything drooping or touching neighbours. Light through the crown should be visible.

Step 5: Cut back side branches

Side branches longer than 30 centimetres: cut to six leaves.

Step 6: Deadwood

Anything brown, black or bark-less: remove. To clean wood.

Step 7: Fruit thinning (June-July)

Thin to one plum per 8-10 centimetres of branch. Less aggressive than Victoria.

Frequently asked questions

Does Opal still grow too fast?

No. Opal stays much more compact than Victoria. Many gardeners eventually find it too small and plant Victoria instead.

Can I thin Opal more to keep it even smaller?

Yes, but unnecessary. Opal naturally sets itself at 2-3 metres. Minimal pruning suffices.

How many plums do I harvest from Opal?

Average 5-15 kilos per tree yearly, depending on age and care. Small plums, but high quality and very sweet.

Why do many gardeners say "Opal is too small"?

Bigger-is-better mentality. Opal yields less volume than Victoria, but far better taste and much less disease.

Can I grow Opal as a palmette against a wall?

Yes, palmette form is possible. Same principle as Victoria, but Opal forms faster.

How many years until first harvest?

Year two already small crop, year three full crop. Faster than Victoria.

Closing: Opal is perfection in miniature

Many gardeners ignore Opal because it is "small." But small means healthy, manageable, low-fuss and exceptional taste. Eight grammes of Opal plums in August is pure gold.

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