HORMI - 202
Production Technology of Cut Flowers
Production Technology of Cut Flowers
UNIT IV
📚 Contents
🌸 Flower Forcing in Cut Flowers
✅ What is Flower Forcing?
Flower forcing is the technique of manipulating environmental or physiological conditions to induce flowering at a desired time, especially during the off-season or for market demand (festivals, events, exports).
✅ Objectives of Flower Forcing:
- Achieve year-round availability of flowers
- Meet market demand and premium pricing windows
- Synchronize flowering for commercial contracts
- Control flowering time in photoperiod-sensitive species
✅ Methods of Flower Forcing:
- Manipulation of Photoperiod:
Short-Day Plants (e.g., Chrysanthemum): Flower under short days. Use blackout curtains to artificially shorten day length.
Long-Day Plants (e.g., Carnation): Use artificial lighting (e.g., incandescent or LED lights) to extend day length. - Temperature Control (Thermoperiodism):
Vernalization: Exposing young plants or bulbs (e.g., Lilium) to low temperatures (4–10°C) for a specific period to break dormancy.
Use of high/low temperature regimes to induce or delay flowering in crops like gladiolus and tulip. - Growth Regulators (covered in next topic):
Plant growth regulators (PGRs) are used to stimulate flower bud formation or speed up development. - Cultural Practices:
Pinching (in chrysanthemum, carnation) to delay or synchronize flowering.
Disbudding to concentrate plant energy into fewer, larger blooms. - Water and Fertilizer Management:
Mild water stress can be used to induce flowering in some crops.
High phosphorus in fertilizers can promote early flowering.
✅ Examples of Flower Forcing:
| Crop | Method | Purpose |
|---|---|---|
| Chrysanthemum | Short-day induction using blackout | Year-round flowering |
| Gladiolus | Cold storage of corms and staggered planting | Staggered flowering |
| Lilium | Vernalization of bulbs | Flower induction |
| Rose | Temperature control & pruning | Continuous blooms |
🌼 Year-Round Flowering Through Physiological Interventions
Year-round flowering is a desirable goal in commercial floriculture to ensure consistent market supply. This can be achieved by influencing the internal physiological processes of the plant that regulate flowering.
✅ Key Physiological Interventions:
1. Manipulating Plant Hormones
Plant hormones regulate critical stages such as flower induction, bud development, and flowering.
| Hormone | Role in Flowering | Application |
|---|---|---|
| Gibberellins (GA₃) | Promote flower stalk elongation, initiate flowering in some crops (e.g., gladiolus) | Foliar sprays (50–100 ppm) |
| Cytokinins | Delay senescence, promote lateral bud development | 10–50 ppm |
| Ethylene Inhibitors | Delay senescence and abscission | Silver thiosulfate (STS), 1-MCP |
| Abscisic Acid (ABA) | Involved in stress-induced flowering in some species | Generally avoided for forcing |
2. Pinching and Disbudding
- Pinching: Removal of apical meristem to break apical dominance and induce lateral branching → uniform flowering
- Disbudding: Removal of side buds to promote large central blooms (e.g., carnation, chrysanthemum)
3. Hardening & Stress Application
- Drought stress can trigger flowering in some species as a survival mechanism.
- Nutrient stress (especially low nitrogen) may help induce flowering in certain crops.
4. Use of Dormancy-Breaking Treatments
- For geophytes (bulbous flowers):
- Cold treatment (vernalization) of bulbs (e.g., tulip, lilium)
- Hormone dips (GA₃ for gladiolus corms)
5. Photoperiodic Treatments
- Use of artificial lighting or shading to control flowering window based on critical day length
✅ Examples of Crops and Interventions:
| Crop | Intervention | Outcome |
|---|---|---|
| Rose | Pruning + temperature regulation | Continuous flowering |
| Carnation | GA₃ spray + pinching | Early flowering & more shoots |
| Gladiolus | Corm treatment + planting schedule | Off-season flowering |
| Chrysanthemum | Photoperiodic control | Year-round blooms |
These interventions regulate the internal cues that guide the flowering process and allow farmers to extend the commercial blooming season effectively.
🧪 Chemical Regulation in Flowering of Cut Flowers
Chemical regulation involves the use of plant growth regulators (PGRs) and other chemicals to control flowering time, flower quality, plant architecture, and post-harvest behavior.
✅ Why Use Chemical Regulators?
- To promote or delay flowering
- Improve bud initiation, flower size, color, and stem strength
- Induce uniform flowering
- Enhance resistance to stress and diseases
- Regulate plant height and branching
✅ Important Chemicals & Their Roles:
| PGR | Function | Application |
|---|---|---|
| Gibberellic Acid (GA₃) | Promotes flowering, stem elongation, breaks dormancy | 50–100 ppm (spray/dip) |
| Cytokinins (BA, Kinetin) | Promote lateral shoot growth, delay senescence | 5–50 ppm |
| Ethrel / Ethephon | Releases ethylene – used to induce flowering in some crops | 250–500 ppm |
| Paclobutrazol | Growth retardant; reduces plant height and enhances compactness | 5–30 ppm (soil drench) |
| Daminozide (Alar/B-nine) | Shortens internodes, promotes compact plants, enhances flowering | 1000–2000 ppm spray |
| Silver Thiosulfate (STS) | Inhibits ethylene action – used to improve post-harvest life | 0.1–0.2 mM solution |
| 1-MCP (1-Methylcyclopropene) | Delays flower senescence by blocking ethylene receptors | 0.5–1 ppm (fumigation) |
✅ Application Techniques:
- Foliar Spray: Most common method; ensures quick uptake
- Soil Drenching: Used for systemic growth regulators like paclobutrazol
- Bulb/Corm Soaking: Used for gladiolus, lilium before planting
- Injection: Rare, but precise for high-value crops
✅ Examples of Crop-Wise Use:
| Crop | Chemical & Dose | Effect |
|---|---|---|
| Rose | GA₃ (100 ppm) | Promotes flowering and stem elongation |
| Carnation | Daminozide (1500 ppm) | Controls plant height, enhances flower quality |
| Chrysanthemum | Ethephon (300 ppm) | Promotes early flowering |
| Gerbera | Paclobutrazol (10 ppm) | Controls excessive vegetative growth |
| Gladiolus | GA₃ (150 ppm) bulb soak | Breaks dormancy, uniform flowering |
⚠️ Precautions:
- Use correct dosages to avoid phytotoxicity
- Apply under suitable environmental conditions (no rain, low wind)
- Protective gear should be used while handling chemicals
🌤️ Environmental Manipulation for Flowering Control
Environmental manipulation involves modifying growing conditions—such as light, temperature, humidity, and CO₂ levels—to influence plant growth and flowering patterns. It is especially useful in protected cultivation to achieve year-round, high-quality flower production.
✅ Key Environmental Factors & Their Manipulation:
1. Light (Photoperiod and Intensity)
- Photoperiodic response affects flowering (SDP, LDP, day-neutral)
- Short-Day Plants (SDP): e.g., Chrysanthemum → Flower under short days (<12 hrs)
- Long-Day Plants (LDP): e.g., Carnation → Flower under long days (>14 hrs)
- Manipulation Techniques:
Blackout curtains for short days
Artificial lighting (e.g., incandescent, LED) to extend daylight
Light intensity is managed using shade nets or reflective materials
2. Temperature (Thermoperiodism)
- Optimal range varies by crop (e.g., Rose: 16–28°C; Gerbera: 18–25°C)
- High temperature can delay flowering or cause bud abortion
- Low temperature (vernalization) induces flowering in bulbous plants like tulip and lilium
- Greenhouses use:
Heaters during winter
Fans and vents or cooling pads during summer
3. Humidity
- Ideal RH: 60–70%
- Low humidity → wilting, bud drop
- High humidity → promotes diseases like Botrytis
- Controlled using:
Fogging/misting systems
Ventilation and dehumidifiers
4. Carbon Dioxide (CO₂) Enrichment
- Ambient CO₂ ≈ 400 ppm; increased to 800–1000 ppm in greenhouses
- Benefits:
Enhances photosynthesis
Increases biomass and flowering - Applied via:
CO₂ generators
Compressed gas cylinders
5. Moisture (Irrigation Control)
- Adequate moisture promotes healthy growth and flower development
- Deficit irrigation may be used for stress-induced flowering in some crops
- Use of:
Drip irrigation
Sensors to monitor soil moisture
Tensiometers and automated irrigation systems
✅ Example: Environmental Control in Common Cut Flowers
| Crop | Environmental Control | Result |
|---|---|---|
| Chrysanthemum | Short-day with blackout curtain | Timed flowering |
| Rose | Temperature & CO₂ enrichment | Continuous production |
| Gerbera | Controlled humidity & light | High flower quality |
| Gladiolus | Cool conditions post-planting | Enhanced spike quality |
✅ Integrated Use in Protected Cultivation:
Environmental manipulation is most effective in polyhouses or greenhouses where:
- Light, temperature, humidity, and CO₂ can be precisely regulated
- Automation systems optimize input usage and crop output