Algae are simple photosynthetic organisms that naturally occur in moist growing environments. While algae themselves rarely harm plants directly, excessive growth can reduce substrate performance, attract pests, and create unfavorable growing conditions. Proper water management and good greenhouse hygiene are the most effective ways to minimize algae growth.
What Are Algae?
Like all plants, algae use sunlight, water, and carbon dioxide to produce energy through photosynthesis. They also require nutrients such as nitrate and phosphate to grow.
- Green algae contain chlorophyll, giving them their characteristic green color.
- Blue-green algae, also known as cyanobacteria, are bacteria rather than true plants.
- Algae commonly develop on the surface of moist growing media where light, water, and nutrients are readily available.
Although algae usually do not damage plants directly, uncontrolled growth can contribute to several secondary problems.
Common Sources of Algae
Algae spores are naturally present in most growing environments and can be introduced from several sources.
- Irrigation water, particularly from ponds or shallow wells.
- Biofilm buildup inside irrigation pipes and water lines.
- Wet greenhouse floors, benches, and walkways.
- Dust and airborne spores entering from outside the greenhouse.
Symptoms
- Green slime or green patches on the surface of the growing medium.
- Green growth around containers, irrigation equipment, or greenhouse structures.
Problems Associated with Algae
- Dried algae can form a surface crust that reduces water infiltration.
- Surface sealing may reduce oxygen availability within the growing medium.
- Moist algae provide an ideal habitat for fungus gnats and shore flies.
- These insects may damage roots or spread plant pathogens.
- Algae growing on greenhouse glazing can reduce light transmission.
Controlling Algae
Inspect the Water Supply
- Regularly inspect irrigation water for algae contamination.
- Clean irrigation systems whenever algae or biofilm are detected.
- Water treatment methods may include chlorine dioxide, copper ionization, or hydrogen peroxide, following local regulations and manufacturer recommendations.
- Water from ponds or shallow wells requires additional monitoring because it often contains higher algae levels.
Reduce Surface Moisture
- Algae require continuous moisture to survive.
- Allow the surface of the Eazy Plug growing medium to dry until it turns light brown before rewatering.
- The naturally self-regulating moisture characteristics of Eazy Plug help create less favorable conditions for algae.
Improve Environmental Conditions
- Increase air circulation to encourage faster surface drying.
- Where appropriate, slightly increasing air temperature can also help reduce surface moisture.
Preventing Algae Growth
Avoid Excessive Watering
- Overwatering is one of the primary causes of algae development.
- Ensure growing media drain freely after irrigation.
- Eazy Plug products naturally regulate their air-to-water ratio, reducing the risk of excessive moisture.
Use Well-Drained Growing Media
- During humid conditions, use light and porous growing media.
- Eazy Plug products maintain consistent porosity throughout the crop cycle.
Maintain the Proper pH
- Most growing media perform best between pH 5.8 and 6.2.
- Eazy Plug products are manufactured with a pH of approximately 6.0.
Reduce Light Exposure on the Growing Medium
- Algae require light to grow.
- Reducing light exposure on the surface of the growing medium can significantly limit algae development.
- Because Eazy Block and Eazy Pyramid are used without plastic sleeves to promote air pruning, mild algae growth may occasionally occur on exposed surfaces.
- Minor algae growth on the outer surfaces of Eazy Block and Eazy Pyramid is generally harmless and often requires no treatment.
Treatment Options
Several non-chemical treatments may help reduce algae growth. Results can vary depending on water quality, growing media, and environmental conditions.
- Water lightly with cooled chamomile tea.
- Mix 1 part hydrogen peroxide with 10 parts water and lightly spray affected areas. Small amounts may also be added to irrigation water where appropriate. Use caution, as excessive concentrations may damage young roots.
- Spray algae with a solution of 2–3 teaspoons of baking soda per 1 litre of water.
- For extensive infestations, commercial algaecides may be considered in accordance with manufacturer instructions and local regulations, particularly when growing edible crops.
Important Notice
Always test any treatment on a small area before applying it across an entire crop. Monitor plant response carefully and use all products according to the manufacturer’s recommendations to avoid unintended damage.