Lighting technique to handle off-season flowering for dragon fruit

Lighting is a decisive step in handling off-season flowering dragon fruit. Instructions for choosing lamp type, bulb density, lighting time, checking flower buds and managing electricity and water to reduce costs but still maintain plant health.

Summary: Lighting dragon fruit is not just about turning on the electricity at night. To flower evenly, the orcharder must prepare the plant's strength, choose the right shade, arrange the light evenly, light enough nights and stop at the right time when the flower buds are clear. Lack of time for scattered flowering plants; Excessive work exhausts the tree and increases electricity costs. This article delves into the technique of lighting a lamp for an off-season.

Applies to: Dragon fruit orchards operating from the 4th year onwards in Binh Thuan, Long An, Tien Giang, Vinh Long, Tay Ninh.
Duration: One period of lighting usually lasts 15-20 nights, followed by another 7-10 days after stopping the lighting.
Difficulty level: Advanced. Need to control electricity, water, nutrition and plant health.
Estimated additional costs: 12-30 million VND per hectare per batch, depending on bulb type, electricity price and number of lighting nights.

Principle of lighting

Dragon fruit blooms strongly in long days and short nights. In the off-season, the nights are naturally longer, making it difficult for plants to differentiate flower buds evenly. Lighting up lights at night helps "cut" the long night, making the plant feel like it is in favorable conditions for flowering.

Points to remember:

Not all plants that light up will flower well. The tree must have enough strength.
Light must evenly cover the canopy, especially the fruit-bearing branches.
The lighting time must be enough for a number of consecutive nights.
After flower buds appear, you need to stop at the right time and switch to bud care.

Lighting is a physiological effect and does not replace fertilization, watering and plant recovery.

Tree conditions before lighting

Should only be lit when the orchard meets the following conditions:

From the 4th year onwards, the canopy is stable.
Just finished harvesting at least 30-45 days.
Green branches, tight, not wrinkled due to lack of water.
The orchard does not suffer from anthracnose, black spots, or heavy mealybugs.
The fertilizer has been restored and there is enough water for irrigation throughout the lighting period.

If the tree has just produced high yields, has a yellow canopy, wrinkled branches or weak roots, you should skip a period of treatment to recover. Pressing weak plants often consumes electricity, but the flower buds are few, the fruits are small, and the next crop clearly declines.

Select lamp type

Incandescent lamp

Typical power 60-100 watts.
Strong light and heat, once commonly used.
Disadvantages: consumes electricity, heat, short lifespan.

Currently, it should only be used when the orchard already has the old system in place and the calculation is still profitable.

Compact lamp

Typical power 15-25 watts.
Much more energy efficient than incandescent.
Lighting is suitable if arranged with sufficient density.
Moderate investment costs.

Compact lights are a popular choice for many commercial orchards because of the balance between investment costs and electricity bills.

Specialized LED lights

Lower power, longer life.
Can choose a more suitable light spectrum.
High initial investment costs.

For large orchards and regular off-season work, LED calculations should be calculated based on 3-5 years, not just looking at the bulb price when buying.

Density and arrangement of shadows

There is no one right number for every orchard. Density depends on pillar spacing, shade type, hanging height and canopy width.

Reference:

System type	Common density	Notes
Incandescent lamp	800-1,200 balls/ha	Consumes electricity, strong light
Compact lamp	1,000-1,800 balls/ha	More economical, requires even coverage
LED Light	800-1,500 balls/ha	Depending on capacity and projection angle

Principles of layout:

Hang the ball about 1.8-2.2 meters high, horizontal or slightly higher than the flower-bearing branch area.
Do not let the dark area extend between the two rows of pillars.
Electrical wires must be neat, have sturdy hanging points, and avoid touching wet branches.
Divide switches into batches for easy control and troubleshooting.

After installation, check at night. Eyes can see dark areas more clearly than during the day on drawings.

One time lighting calendar

Prepare to light 10-15 days in advance

Pruning diseased branches and too dense branches.
Fertilize to stimulate flowering: increase phosphorus and potassium, do not push nitrogen too strongly.
Spray calcium — boron 1-2 times if the orchard lacks trace elements.
Water sufficiently, avoid letting the plant dry before turning on the light.
Check bulbs, wires, circuit breakers, prevent electric leakage.

Lighting stage

Reference calendar:

Light 7-10 hours every night, usually from 9-10 p.m. to 4-5 a.m.
Light continuously for 15-20 nights depending on variety, plant health and weather conditions.
If it rains or has high humidity, you still have to ensure electrical safety first before maintaining the schedule.

Some orchards have a shorter process, but you should not shorten the time unless you try it on a small batch and record the results. Lack of time often causes flower buds to bloom unevenly.

When flower buds appear

After about 12-18 nights, check the branches:

Good flower buds: clear, round, tight buds, evenly positioned on the branch.
Weak sprouts: small, sparse, dry tips.
If the sprouts have sprouted evenly, prepare to stop the lights as scheduled.

Do not prolong lighting too much just because you want more sprouts. A tree that produces too many flowers will have to be pruned, which wastes electricity and exhausts the tree.

Manage water and fertilizer while lighting

Water

The off-season usually falls during the drier period, so water determines the germination rate:

Keep the soil moist enough, don't let it dry out around the base.
Water lightly and evenly, avoid watering too hard and then letting it dry.
Sandy soil orchards require shorter irrigation cycles than alluvial soils.

A plant that lacks water may still sprout, but the buds will dry, fall off, or have small flowers.

Feces

Before and during the lighting:

Do not fertilize with high nitrogen because the plant will produce young branches instead of flowers.
Prioritize phosphorus, potassium, calcium — boron according to orchard conditions.
After the flower buds are clear, gradually switch to nutrition to nourish the buds and nourish the fruit.

Do not apply too much fertilizer at once. Dragon fruit roots are shallow and easily shock when the soil is dry.

Electrical safety in the orchard

Lighting is a technique that has electrical risks, especially when the orchard is damp or there is unseasonal rain:

Use outdoor power cords with the correct load.
There is a leak-proof circuit breaker if conditions allow.
Joints must be covered, hung high, not placed close to the ground.
Do not repair electricity with wet hands or in the rain.
Periodically check for cracked bulbs, loose bulbs, and mouse-bitten wires.

An electrical fault can burn out a whole batch of wires or cause an accident for the orcharder. Don't skimp on wires and electrical protection.

Evaluate the results after lighting

After stopping the light for 7-10 days, evaluate:

Proportion of branches with flower buds.
Average number of sprouts per cylinder.
Consistency between batches.
Proportion of sprouts drying or falling off.
Actual electricity costs per night and in installments.

If there are few sprouts in one area, check that area for lack of light, lack of water, weak plants or damaged bulbs.

Common mistakes

Light when the tree has not yet recovered: few sprouts, small fruit, tree decline after the season.

Uneven arrangement of bulbs: rows near the bulb flower, dark rows do not bloom or bloom late.

Reducing the number of lighting hours based on feeling: saves a little electricity but loses the entire flower season.

Do not calculate electricity bills before work: off-season price fluctuations, high electricity costs can eat up all profits.

Abolishing electrical safety: poor wiring, open connections, not dividing lots, making incidents difficult to control.

Mandatory notes

[ ] Starting and ending date of lighting.
[ ] Type of bulbs, capacity, number of bulbs per hectare.
[ ] Number of lighting hours per night.
[ ] Electricity costs in installments.
[ ] Percentage of branches with flower buds after 7-10 days.
[ ] Yield and selling price of the reverse wave.

After a few batches, orcharders will know which lot reacts well, which bulb type is really economical and which lighting schedule is suitable for their orchard.