Lecture 12: Horticulture Structures

Types of Greenhouses

  • Not so much types, but architectural designs.

    • Quonset Style: Semi-circular arch design.

    • A Frame: Triangular design; can come in various forms.

    • Lean-To: Attached to another building for space efficiency.

Commercial vs. Hobby Greenhouses

  • Commercial Greenhouses:

    • Typically metal structures.

    • Glazing materials: Plastic sheets, Lexan panels.

    • Historically included fiberglass, but now not a top choice due to fire hazards.

  • Hobby Greenhouses:

    • Can vary widely in construction (wood, metal, plastic).

    • More flexible in design; may incorporate stone or concrete.

Glazing Options

  • Glass:

    • Best light transmission.

    • Most expensive, challenging to replace if damaged.

  • Lexan Panels:

    • Good longevity and decent light transmission.

  • Polyethylene:

    • Less expensive, but requires more frequent replacement.

Greenhouse Design Considerations

  • Size: Available in kits ranging from small (4x4) to large scale (acres).

  • Custom Greenhouses:

    • May include custom framing and glass purchased affordably from glass shops.

Equipment and Functionality

  • Greenhouse objectives revolve around creating a controlled environment for plants:

    • Temperature Regulation: Essential in most climates.

    • Humidity Control: Critical for specific types of plants (e.g., tropical vs. succulents).

    • Lighting Needs: Use of grow lights depending on plant types (day neutral, long day, short day).

    • Atmospheric Control: Managing gases such as CO2 for optimal photosynthesis.

Common Greenhouse Structures

  • Freestanding vs. Attached Greenhouses:

    • Freestanding: Standalone structures.

    • Attached: Often for smaller setups like sunrooms.

  • Hoop Houses:

    • Simple design, usually applicable for season extension and seed-starting protection.

Construction Materials

  • Frame Materials:

    • Wood: Use rot-resistant types (e.g., redwood, cedar).

    • Metal: More common for commercial use.

    • Concrete: Used for base structures.

  • Foundation Choices:

    • Must accommodate environmental load (wind, snow).

Operational Considerations

  • Water Supply:

    • Importance of water quality (potential city water treatment issues).

  • Power Needs:

    • Consider a subpanel of 60-100 amps for heavier equipment.

Environmental Controls

  • Ventilation Techniques:

    • Passive: Using automatic temperature actuated mechanisms.

    • Active: Forced air or negative pressure systems for cooling.

  • Heating Systems:

    • Electric, gas, or renewable sources (e.g., solar).

  • Shading and Covering:

    • Materials can reduce light transmission and trap heat.

Additional Horticultural Structures

  • Cold Frames:

    • Used for seed starting without the full cost/space of a greenhouse.

    • Made using simple materials (plywood, old windows).

  • Hot Frames:

    • Essentially cold frames but heated (could be electric or use compost for heating).

  • Shade Structures/Lath Houses:

    • Provide moderate shade for transitioning plants and protecting from harsh weather.

Maintenance Challenges

  • Expect maintenance demands to rise with sophistication:

    • Issues with motors, fans, heating systems, and cooling pads over time.

  • Be prepared for the longevity balance between usability and functional complications.

Conclusion

  • Evaluative Questions:

    • What will the greenhouse be used for?

    • Are you ready for the commitment of maintenance?

    • Will you grow on a temporary or permanent basis?