Pruning finger lime, scaffold vs productive branches

Pruning a finger lime tree helps get healthy, tasty fruits year after year.

It also protects this delicious but vulnerable citrus from diseases and pests. Here is how to prune your Australian finger lime.

Key finger lime pruning facts

Season – after harvest (autumn)
How often – yearly
Main concern – suckers, distance to ground
Watch for – gall wasp swells

Make it a regular task visit your finger lime with secateurs, ideally monthly. Pruning a little at a time is easier on the tree than a single heavy pruning every year.

Ideal shape for a finger lime tree

Three important facts guide the pruning shape your Australian finger lime should have:

• Finger lime fruits are hand-picked from the tree.
• Sun helps fruits mature.
• Air circulation reduces diseases and pests.

Although finger lime is less vigorous than most other citrus varieties, it still does need regular pruning. The ideal shape you should try to aim for has the following characteristics:

• Clear trunk up to knee-height (18 inches or 45 cm). If grafted, make sure nothing sprouts from under the graft joint.
• Four to six main branches, evenly spread in all directions at about waist height. Usually the main trunk is nipped off at about 2-3 feet or 60-90 cm height.
• Secondary branches form a canopy shaped like a flat cup.
• In time, a mature, 15-year old tree would be kept 8-10 feet (2.5-3 meters) wide and 6 to 8 feet tall (2 to 2.5 meters). It might take a decade to grow that large.
• Finger lime is very thorny, with fragile fruits. Branches should be thinned for the tree to be somewhat “see-through”.

Best is to circle around the tree every month to trim any shoots or branches that don’t fit into this shape. Bring thick gloves with you as the thorns are sharp.

When to start pruning finger lime

Start pruning your finger lime early on.

• Pruning as early as year 2 or 3 will form the tree without much effort. Citrus wood is hard, so pruning while small is easier.
• Finger lime, if unpruned, will grow into a random thicket of thorns. It will be difficult to correct, and impossible to harvest fruit.
• Once the tip has grown to 2-3 feet high (60-90 cm), you can start selecting and favoring the structural branches.

In later years, for maintenance pruning, wait until after the harvest to perform most of the pruning, especially if you’re “catching up”.

• This is simply because new flowers haven’t formed yet: you won’t be compromising the harvest.

Year-round pruning

During the rest of the year, you can perform follow-up pruning as often as you wish. Check and adjust the shape every month to avoid heavy pruning.

Steps to prune finger lime

Pruning isn’t simply about giving the tree the ideal shape. It also helps control pests, fruit quantity and quality, and diseases. Go through these steps to check what should be removed.

Australian finger lime doesn’t like extreme pruning. Never remove more than a third of the tree in one go. Always keep some live branches at the tip of structural branches to make sure sap circulates.

How to prune finger lime

There are 3 types of branches on your finger lime tree:

• large, permanent scaffold branches
• smaller production branches (replaced with new growth)
• suckers that pop out from below

1. Structural branches – as horizontal as possible, evenly fanning out from the trunk in all directions. Mark them with a yarn or loose tag for the first few years.

2. Secondary branches – keep one or two that are the most horizontal at the tip of each structural branch.

• These will extend the structural branch in the following years.
• If two branches cross or touch each other, remove the one that’s the most upright.
• Remove any branches that are growing back inwards to the inside of the tree or towards the trunk or center.

Remove these: Inwards – Crossing – Upwards. As in, “I see you, ICU!”

3. Suckers – Remove all shoots that appear straight from the trunk. You can keep one if you need to create a new structural branch, but make sure it sprouted above the graft joint.

Growth issues with too many suckers?

If lots of branches start growing in random directions, mostly from lower trunk, it is the result of insufficient availability of boron trace elements.

Indeed, most citrus are vulnerable to loss of apical dominance. Boron deficiencies increase this problem. New shoots come from the lower trunk upon pruning, instead of branching out from the tip of the tree. This results in a hard-to-train tree that is more vulnerable to disease.

• Recent research indicates that applying small amounts of seawater can restore boron elements in soil.

Tips and tricks about pruning Microcitrus australasica

You’ll run across these ideas as time passes, it’s a good idea to practice them early on:

Skirting

Skirting – The “skirt” of the tree is how low the branches reach. Cut any branch that hovers lower than knee-height (2 feet or 60cm). Skirting reduces insects and fungal diseases.

Thinning branches

Thinning aims to reduce the density of the tree canopy. In particularly dense spots that block out light and air, remove one in four or one in three secondary branches. A breeze should filter through the tree and not run around it. Sunlight should land on branches in the middle of the tree. Thinning spreads out pest insects and makes predator insects more effective (especially against thrips, for instance).

Dead wood and pest-infested branches

Dead wood – cut dead wood back to the nearest joint. Cut small twigs and scraggly growth off from main branches, too.

Pests – If ever you notice swelling along a branch, check for gall wasps. Cut out and burn or suffocate contaminated branches in a black sack set for days in hot sun.

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