Pruning and raising durian fruit: keeping the yield within the tree's capacity

Pruning durian fruit determines 50-60% of the quality and true economic yield. A tree with 150 fruits cannot be equal to 80 quality fruits. Instructions on three times of pruning and fruit raising process for orchards in the Southwest and Southeast.

Summary: The most common mistake in a new durian orchard is being greedy for the fruit. The tree holds 150-200 fruits for the "beautiful" season shown in the photo, but the fruits are small, the rice is uneven, the selling price is low, and the tree is exhausted in the next crop. Trees holding 60-100 high-quality fruits can sell for 30-50 percent more. This article guides three times to prune fruit and how to raise fruit at the end of the season.

Applies to: Ri6 durian, Monthong, Musang King, Thai Dona durian in the Southwest and Southeast. Business tree 7 years old or older.

Duration: From young fruit set to harvest — about 4-5 months.

Difficulty level: Advanced. Requires experience in assessing the ability of plants to grow.

Estimated additional costs: 2-4 million VND per hectare for fruit pruning + nutritional supplies.

Why pruning fruit is not a choice but a discipline

Each durian tree has a limited "energy budget" — photosynthesis from the leaves creates nutrients that are distributed to the roots, trunk, branches, new leaves and fruit. When keeping too many fruits:

• The fruit is not nutritious enough — small size, sparse flesh, large seeds.
• The tree puts all its capital into fruit — it cannot accumulate resources for the next year, causing the tree to "sleep".
• The rate of fruit drop increases — there is not enough nutrition to feed the tree, so the tree self-eliminates.
• The fruit-bearing branches are fragile — especially with Monthong and Musang King, the fruit weighs 4-7 kilograms.

Properly pruned orchards often have the same or higher total yield than unpruned orchards — because of quality fruit + high prices + more durable trees.

The rule for the number of fruits depends on the strength of the tree

This is a frame of reference — the actual tree needs its own evaluation:

The number left and right is included:

• Ratio of leaves/fruit: minimum 15-20 active leaves for 1 fruit.
• Current tree health: tree has recently experienced disease or drought — reduced by 30-40 percent compared to the norm.
• Market target: high quality fruit for export — reduce fruit quantity by 15-20 percent.

Trim the fruit three times

Preliminary pruning — 25-30 days after fruit set

The young fruit is the size of a duck egg. Goal: remove fruit that is unable to develop.

Pruning:

• Deformed fruit — distorted, misaligned, unbalanced ends.
• The fruits grow crowded together — two or three fruits grow close together.
• Fruit stalks are soft, showing signs of fungus.
• Fruits grow towards the sky — easily fall due to gravity + sunlight.

Prune lightly at this stage — only remove 20-30 percent of the fruit. The tree still needs "many fruits" to naturally filter itself.

Selective pruning — 45-60 days after fruit set

The fruit is the size of a chicken egg. This is the most important pruning.

Goal: reduce the number of fruits to the final goal.

Pruning according to the principle:

• Count the number of fruits on each fruit-bearing branch. Rule: 1 fruit for 15-20 active cards.
• Remove the fruit with thin, small stems: firm, dark red stems are good. Thin, pale stems will fall off prematurely or produce poor fruit.
• Unevenly shaped fruit: distorted, crooked, unbalanced.
• Keep the fruit round and balanced, growing downward or horizontally.

After this pruning, the number of fruits is only 60-70 percent compared to after preliminary pruning. The tree focuses on raising the remaining fruit.

Final pruning — 75-90 days after fruit set

The fruit is the size of a small bowl. Final light pruning.

Goal:

• The fruit grows noticeably slower — 30-40 percent smaller in size than the average fruit.
• Discard fruit that shows signs of borers or fungus.
• Check the stems again — which ones are browning and falling off prematurely.

After this time, the number of fruits is fixed until harvest.

Cultivate fruit after final pruning

Nutrition

The fruit growing stage (after pruning to before harvest) requires:

• Potassium: the most important element. Apply Potassium sulfate (K2SO4) 0.3-0.5 kg per tree, divided into 2 times every 25-30 days.
• Calcium-Boron: spray leaves 2-3 times every 10-14 days. Increases fruit pulp strength, reduces peel cracking.
• Magnesium + trace elements: spray leaves 1-2 times. Increase the quality of rice.
• Avoid nitrogen: applying nitrogen at the end of the season causes plants to push out young shoots — competing with fruit.

Water Management

• Regular, stable watering: neither sudden dryness nor waterlogging. Water fluctuations at the end of the season cause fruit peel cracking.
• 7-10 days before harvest: reduce watering by 50-70 percent so that the fruit concentrates starch into rice. Watering too much at the end of the season makes the rice mushy and with large grains.

Cover the left or cover the left

For trees for export or high price:

• Cover with a mesh bag: avoid fruit borers, prevent sunburn. 5,000-10,000 VND per bag depending on size.
• When will the fruit be the size of a watermelon (100-120 days after fruit set).
• Do not cover with sealed plastic — the fruit lacks air and is susceptible to fungus.

Supports fruit-bearing branches

Durian fruit weighing 3-5 kilograms puts great pressure on the branches. Support:

• Hanging rope: use a flexible plastic rope to hang the fruit on a stiffer parent branch.
• Stake stake: place a stake under a branch bearing heavy fruit.
• Watch the branches — branches that start to bend a lot need support right away, don't wait for them to break.

Monitor the fruit growing stage

• [ ] Fruit drop rate — target less than 5 percent after final pruning.
• [ ] Fruit size increases steadily every week.
• [ ] Shell color and shine — dark green shell, strong spines.
• [ ] Stem condition — dark red is good.
• [ ] Are buds appearing on the tree — there should not be many buds at this stage.

Handling problems at the end of the case

Fruits develop unevenly, some are clearly small: check nutrition, especially potassium. Spray additional potassium nitrate (KNO3) 1 percent 1-2 times.

The tree buds at the end of the season: slight tree stress — stop watering for 5-7 days. Spray 1 percent potassium nitrate. Prune buds by hand.

Cracked fruit: usually due to heavy watering followed by drying. Keep evenly moist, avoid watering too much.

Fruit falls suddenly: check the stem for fungus. Spray to prevent stem fungus.

Fruit borers appear: spray the original treatment *Emamectin benzoate* for trees without fruit covers. Check the bag to see if it is torn.

Assess harvest time

Durian ripens unevenly — must be harvested in batches. Signs of ripe fruit:

• The stem is starting to turn slightly yellow — ready to separate.
• The thorns are less sharp, slightly soft when pressed — the fruit is ripe.
• Slight fragrance wafts from the fruit — especially early in the morning.
• The skin changes color slightly — Ri6 from dark green to light green, Monthong from dark brown to light yellow.
• Clapping hands sounds like a deep "death" — not the "bang" sound of unripe fruit.

Important: do not cut unripe fruit prematurely. Durian fruit cut prematurely ripens without real flavor, selling at a low price of 30-50 percent.

Common mistakes

Hold on fruit when pruning: want good but bad results — small fruit, sparse rice, low price.

Pruning too early by counting on paper: it is not known which fruit will fall naturally. Preliminary pruning should only be 20-30 percent.

Using nitrogen at the end of the season "gives big fruit": counterproductive. The tree does not bud, the fruit is poorly nourished.

Irrigate thoroughly before harvest: rice is mushy, big seeds. Fruits are sold at low prices.

Skip branch support: branch suddenly breaks and loses 5-10 large fruits — big damage.

Take notes

• Pruning date, number of fruits removed each time.
• Last number of fruits kept on the tree + trunk diameter + tree age.
• Average weight of each harvest.
• Ratio of type A, type B, type C fruit.
• Sales price and revenue.

Several crop data helps refine fruit pruning rules for private orchards.

References

• *Durian farming techniques* — Southern Fruit Institute, 2023.
• *Instructions for pruning flowers and durian fruit* — Department of Horticulture, 2022.

Related articles

• Durian orchard management during flowering and fruit setting
• Pollination and keeping young durian fruit
• Harvesting and sorting durian
• Durian price tracking and 30-day forecast