Instructions for handling off-season flowering for dragon fruit

Dragon fruit flowers naturally from May to November when the nights are short. To have flowers and fruits from December to April (2-3 times higher price), you need to light a pressure lamp. Instructions on lighting techniques and off-season flower management for commercial orchards in Binh Thuan, Long An.

Summary: Off-season flowering is a way to "trick" dragon fruit into flowering during the dry season (December-April) by lighting at night to prolong the plant's biological "day". The price of off-season dragon fruit is usually 2-3 times higher than the main season. However, this technique consumes electricity, requires investment in lighting systems, and overuse can quickly exhaust the tree. This article guides standard procedures + economic considerations.

Applies to: Dragon fruit orchards operating from the 4th year onwards in Binh Thuan, Long An, Tien Giang. Trees under 4 years old should not be pressed.
Duration: One session lasts 18-22 days. One attack can have 2-3 waves.
Difficulty level: Advanced. Need investment + close monitoring.
Estimated additional costs: 15-30 million VND per hectare for one lighting session (electricity + labor + nutrition).

Principle of off-season flowering

Dragon fruit is a short-day photoperiod plant — it flowers when the natural night is longer than 12 hours. In the dry season of December-4, days are 13-14 hours long, nights are only 10-11 hours — the tree does not flower on its own.

Lamp lighting technique:

Light up a night light for 4-5 hours in the middle of the night to "break the long night".
The night-sensing plant is cut into 2 short segments — activating the flowering mechanism.
After 15-25 days of lighting, flower buds appear.

This is not "forcing" the season through treatment — it's just creating artificial light conditions.

When should you force a counter-season

Tree conditions

Trees from 4 years old and up, stable business.
Healthy plant — dark green leaves, no disease.
The previous crop has been collected at least 30-45 days ago.
Fill with adequate nutrients.

orchard conditions

There is a stable power source.
Invested in lighting system.
Sufficient water sources for dry season irrigation.

When you shouldn't force

The tree has just passed the high-yield season: the tree is exhausted, needs rest.
Trees show signs of disease: anthracnose, black spots → treat the disease first.
Last main crop low price + high reverse pressure: calculation is not profitable.
Trees under 4 years old: the plant is still young, pressing it too hard will slow down long-term development.

Lighting system

Lamp type

75-100 watt incandescent lamp: old, consumes electricity, rarely used today.
Compact lamp 20-30 watts: saves 60-70 percent electricity compared to incandescent lamps. Popular.
Dedicated LED lights 12-18 watts: most economical, long lasting, expensive initially.

Recommended: 23-28 watt compact lamp or 12-15 watt LED for red-orange light (600-700 nanometer wavelength).

Installation

Lights installed between dragon fruit pillars, 2-2.5 meters high.
Distance between lights 4-5 meters.
Density of 80-120 lights per hectare depending on light capacity.

Lighting calendar

Light 5-7 consecutive nights for the first time, then 3-4 intermittent nights.
Lights for 4-5 hours every night — usually from 10pm to 2-3am.
A total of 12-15 nights of lighting in one session.

Process of one round of reverse compression

Prepare before lighting (10-15 days)

Fertilize to stimulate flowering: *N-P-K* 6-30-30 or 10-50-10, dose 200-300 grams per cylinder.
Spray leaves *Calcium-Boron* 1-2 times — prepare flower buds.
Water well enough.
Check the lighting system — burned out lights, broken wires need to be replaced first.

Lighting stage (15-22 days)

Light the 1st night to the 7th night in a row.
The 8th to 15th nights are lit intermittently (2 nights lit and 1 night off).
Watch for flower buds appearing on branches — signs seen after 12-18 nights of lighting.

After the flower buds become clear (5-7 days after stopping lighting)

Flower buds are full → stop lighting.
Continue fertilizing and watering normally.
Spray to prevent anthracnose 7-10 days before flowers bloom.

Flowers bloom and fruit

Flowers bloom 18-22 days after stopping lighting.
Natural pollination through bats and night insects.
Fruit setting rate is 60-80 percent when conditions are favorable.

Cultivate fruit and harvest

Fertilizer for fruit: *N-P-K* 12-12-17, 100-150 grams per column.
Foliar spray potassium nitrate (KNO3) 1 percent 1-2 times.
Harvest 28-32 days after flowers bloom.

Yearly calendar

Commercial orchards can force 2-3 inversions per year:

Part 1 (for Lunar New Year):

Lighting: late October to mid-November.
Harvest: late December to mid-January.
Highest price because it's close to Tet.

Phase 2 (late January to March):

Lighting: late December to mid-January.
Harvest: February-March.

Phase 3 (mid-March to April):

Light up: February
Harvest: April
Before the natural harvest (May).

Note: do not force all 3 times in a row — the tree will be too exhausted. Choose 2 optimal batches according to orchard + market conditions.

Monitor and resolve issues

Little or no flower buds appear

Cause:

The tree is not strong enough (just passed the high yield season).
Insufficient nutritional fertilizer before lighting.
Lighting is uneven — dark areas cannot stimulate.

Fix:

Increase fertilization to stimulate flowering.
Check the light distribution.
If the tree is too weak — skip the inversion, let the tree rest.

Dried flower buds fall off

Cause:

Water stress during germination stage.
Spray while the sprouts are growing.
Pests attack sprouts.

Fix:

Irrigate evenly, without shock.
Avoid spraying during the germination stage.
Check periodically for aphids.

The fruit is smaller than the crop

Normal — off-season is usually 10-15 percent smaller than on-season. In return, the price is higher.

Economic Evaluation

Cost of one inversion

Electricity: 8-15 million VND (depending on electricity price and type of light).
Light lighting + management: 2-3 million.
Additional supplies (flower distribution + treatment): 3-5 million.
Lamp depreciation: 1-2 million.

Total: 15-25 million per hectare per batch.

Productivity of an inversion

8-15 tons of fruit per hectare depending on care + tree age.
30-40 percent lower than the deal.

Selling price

Average deal price is 8-15 thousand VND per kilogram.
The price of the crop is 20-40 thousand VND per kilogram.
On Lunar New Year, it can go up to 50-80 thousand VND.

Real profit

A successful inversion: profit of 80-150 million per hectare (after deducting costs).
About 50-100 percent higher than the average.

However, there are risks:

The plant does not react or reacts weakly — electricity costs are not recovered.
Price fluctuates — Tet peak passes quickly.
The tree becomes exhausted if pressed too many times.

Common mistakes

Forcing young trees under 4 years old: long-term slow growth, reduced economic life.

Forcing all 3 negative waves + 6 positive waves in a year: the tree is exhausted, after 3-5 years the yield drops sharply.

Not lighting enough hours or irregularly: flower buds do not come out or come out sporadically.

Insufficient watering during the dry season when pressing back: plants are stressed by water, flower buds fall off.

Skip spraying to prevent anthracnose: sprouts and flowers are susceptible to fungus and widespread loss.

Take notes

Lighting period — start date, end date, number of nights.
Proportion of branches with flower buds.
Rate of fruit set and drop.
Yield + batch selling price.
Actual costs.

References

*Techniques for handling off-season flowering of dragon fruit* — Southern Fruit Institute, 2023.
*Commercial dragon fruit production* — Department of Crop Production, 2022.