Ornamental plants form a vital part of Kenya’s horticultural industry, contributing significantly to both local beautification and export earnings. The quality and longevity of these plants after harvest directly influence market value and customer satisfaction. Effective post-harvest practices ensure that ornamental plants maintain their aesthetic appeal, reduce losses, and meet the stringent quality standards demanded by both domestic and international markets. This chapter explores the essential post-harvest procedures that horticulture professionals must master to optimize the value chain of ornamental plants.

4.1 Post-harvest practices

Post-harvest management is critical in preserving the quality of ornamental plants from the moment of harvest until they reach the consumer. In Kenya’s floriculture sector, especially among cut flowers and potted plants destined for export or local markets, improper handling can lead to significant economic losses. Understanding the biological and environmental factors that influence plant deterioration helps in designing effective care protocols. This section covers the major aspects of post-harvest practices that horticulturists need to apply to maximize shelf life, appearance, and profitability.

4.1.1 Harvesting techniques and timing

The success of post-harvest handling begins with how and when ornamental plants are harvested. Harvesting at the correct developmental stage and using appropriate techniques minimizes damage and extends vase life or shelf life.

Optimal Harvest Timing

• Maturity stage selection: Plants harvested at the proper maturity stage, such as flower buds just before full bloom, tend to last longer. For instance, rose growers supplying Nairobi’s flower markets harvest buds when petals are tight to ensure freshness.
• Time of day: Early morning harvesting is preferred because cooler temperatures reduce water loss and wilting. At a county government nursery, staff schedule harvesting between 6 am and 9 am to maintain turgidity.
• Avoidance of stress periods: Harvesting during extreme heat or drought stresses plants, accelerating senescence. Therefore, harvesting is avoided during midday heat, especially in arid regions like parts of Eastern Kenya.
• Plant part selection: Only healthy, undamaged parts are harvested; damaged leaves or flowers increase decay rates during storage and transport.
• Consistency in harvest intervals: Regular harvesting prevents over-maturity and maintains a steady supply, as practiced by commercial flower farms around Thika.

Proper Harvesting Techniques

• Use of sharp tools: Clean, sharp knives or secateurs reduce tissue crushing and infection risk. One Nairobi-based floral cooperative trains workers to sterilize blades with alcohol regularly.
• Cutting angle: Cutting stems at a 45-degree angle increases the surface area for water uptake and prevents stem base damage.
• Immediate hydration: Placing cut flowers or foliage into clean water immediately after cutting prevents air embolisms that block water transport.
• Minimizing mechanical injury: Gentle handling reduces bruising and tearing, which are entry points for pathogens.
• Sanitation: Harvesting tools and containers are cleaned daily to prevent cross-contamination, a practice emphasized in university horticulture departments.

4.1.2 Cleaning and grading of ornamental plants

Post-harvest cleaning and grading are crucial steps to enhance the visual appeal and marketability of ornamental plants. These processes remove contaminants and separate products by quality standards.

Cleaning Procedures

• Removal of soil and debris: Washing roots of potted plants or rinsing cut foliage removes soil particles that harbor pests or diseases. For example, a flower farm near Nakuru uses filtered water sprays for cleaning before packing.
• Sanitization: Using mild disinfectants like diluted sodium hypochlorite helps reduce microbial loads on surfaces without damaging plant tissues.
• Dust removal: Soft brushes or air blowers clear dust from delicate flowers, improving their appearance.
• Drying: Proper drying after washing prevents fungal growth during storage; this is done in shaded, ventilated areas at many horticulture nurseries.
• Inspection for pests: Cleaning is combined with visual checks for pests such as aphids or thrips, ensuring only pest-free plants proceed to grading.

Grading Criteria

• Size uniformity: Plants and flowers are sorted by size to meet customer preferences and packaging requirements. For instance, hotels in Mombasa request uniform pot sizes for decorative plants.
• Color quality: Grading includes assessment of color vibrancy and uniformity, critical for cut flowers destined for export.
• Stem length: For cut flowers, stem length grading facilitates appropriate bouquet assembly.
• Health and vigor: Only plants free from disease symptoms or mechanical damage are graded as top quality.
• Stage of development: Flowers are grouped by bloom stage to optimize display life and customer satisfaction.

4.1.3 Handling, packaging, and storage

Proper handling, packaging, and storage are essential to maintain the quality of ornamental plants after harvest, especially during transport and market display.

Handling Practices

• Gentle handling: Minimizing physical stress such as bending, crushing, or shaking preserves tissue integrity. Workers at a retail nursery in Kisumu are trained to carry pots using two hands to avoid spills and breakage.
• Hydration maintenance: Keeping cut flowers in water or moist conditions prevents wilting during handling.
• Temperature management: Cooling plants immediately after harvest slows metabolism and delays senescence. Cold rooms at a Nairobi flower auction house maintain temperatures of 2-4°C for roses.
• Avoiding ethylene exposure: Ethylene gas accelerates flower aging. Handling areas are kept ethylene-free by good ventilation and separation from fruit storage.

Packaging Methods

• Packaging materials are selected to minimize mechanical damage while allowing airflow and moisture retention.
• Proper cushioning inside boxes prevents stem breakage.
• Labeling includes handling instructions and destination details to ensure careful transport.

Storage Conditions

• Temperature control: Most cut flowers require cool storage between 2°C and 8°C to prolong freshness.
• Humidity regulation: Relative humidity of 85-95% prevents desiccation without promoting fungal growth.
• Light exposure: Storage in low light conditions reduces photosynthesis and metabolic rates, extending vase life.
• Air circulation: Adequate ventilation prevents buildup of ethylene and heat.
• Duration limits: Storage time is minimized to reduce quality loss, with some flowers like carnations lasting up to 14 days under ideal conditions.

4.1.4 Treatments to extend shelf life and quality

Post-harvest treatments help in maintaining ornamental plants’ freshness and appearance by slowing deterioration and controlling pests or diseases.

Hydration Treatments

• Use of clean water: Hydrating cut stems in clean, fresh water immediately after harvest ensures continuous water uptake.
• Addition of preservatives: Solutions containing sugar, biocides, and acidifiers (e.g., commercial floral preservatives) supply energy, reduce microbial growth, and maintain pH.
• Pulse treatments: Short-term immersion in preservative solutions enhances uptake and prolongs vase life.

Chemical Treatments

• Ethylene inhibitors: Compounds like silver thiosulphate delay senescence by blocking ethylene action, widely used in floriculture farms supplying Nairobi markets.
• Fungicide dips: Prevent fungal infections such as Botrytis, especially important in humid environments like coastal flower farms.
• Growth regulators: Application of gibberellins or cytokinins can improve flower opening and longevity.

Physical Treatments

• Refrigerated storage: Cooling slows metabolism and respiration rates.
• Modified atmosphere packaging: Adjusting oxygen and carbon dioxide levels in packaging reduces oxidation and microbial activity.
• Vacuum packing: Used for some specialty plants to extend freshness during long transport.

Biological Treatments

• Use of beneficial microbes: Some farms employ antagonistic bacteria to suppress post-harvest pathogens.
• Natural extracts: Application of plant-based antifungal agents is gaining interest as a sustainable alternative.

Chapter Summary

This chapter covered the essential post-harvest practices critical to maintaining the quality and longevity of ornamental plants after harvesting. It explored key procedures such as cooling, freezing, drying, grading, sorting, packaging, storage, and transportation, each playing a vital role in preserving the aesthetic and commercial value of the plants. The discussion then shifted to modern marketing techniques including online marketing, influencer marketing, and public relations, which are increasingly important for reaching customers and enhancing sales. Waste management was addressed as a necessary component to ensure environmental sustainability and operational efficiency in ornamental plant production. Practical guidance was provided on how to implement various post-harvest methods effectively, alongside proper handling and disposal of waste using appropriate tools, equipment, and materials. The chapter emphasized an integrated approach combining technical practices and management strategies to optimize post-harvest outcomes in the ornamental plant industry.