How To Build A Greenhouse In Arkansas For Year-Round Gardening

Why a greenhouse is a smart investment in Arkansas

Building a greenhouse in Arkansas gives you control over temperature, humidity, and pests, extending your growing season well beyond the outdoor frost dates and cooling season in summer. Arkansas’ climate ranges roughly from USDA hardiness zones 6b to 8a, meaning winters are generally mild but summers are hot and humid. A properly designed greenhouse converts that climate into a reliable year-round environment for vegetables, herbs, flowers, and tropical plants.

Before you build: local considerations and permits

Selecting the right site and confirming local regulations will save time and money. Arkansas counties and municipalities vary on zoning and building codes. Many smaller greenhouses do not require a building permit, but anything with mechanical heating, plumbing, or electrical systems often does.
Check utility access and whether the property is in a floodplain, wetland, or subject to restrictive easements. Also consider homeowner association rules. If you are in a region of Arkansas with tornado risk, you may need stronger anchoring and impact-resistant glazing or to follow more stringent wind-load design practices.

Site selection: sunlight, drainage, wind, and access

Choose a site with maximum unobstructed southern exposure for passive solar gain. Aim for at least 6 to 8 hours of direct sun in winter when the sun is lower. Avoid heavy shade from large trees and place the ridge line east-west where possible to equalize sun on both sides.
Good drainage is essential. Do not site a greenhouse in a low spot where water pools. Slight slope with drainage swales or buried perforated drainage tile will protect the structure.
Consider prevailing summer winds and storms. Orienting the structure to reduce cross-wind exposure and placing windbreaks or fencing can reduce structural stress and heat loss. Also plan for convenient access to water and electricity for pumps, fans, and heating systems.

Choosing the right greenhouse type and size

Decide on the types of plants and level of automation before you pick a size. Common options include:

• Cold frame or hoop house for season extension only.
• Lean-to greenhouse attached to a heated house for shared utilities.
• Freestanding A-frame or Quonset greenhouse for full control and space.

Size matters for microclimate stability. A larger volume will retain heat and humidity better than a small box. A practical hobby greenhouse for year-round production in Arkansas is often 10 by 20 feet or larger. Commercial operations scale up accordingly, with bench layout and aisle spacing planned for workflow.

Structural materials: frame, glazing, and foundation

Choose materials that balance budget, durability, and insulation.
Frame options:

• Pressure-treated wood: economical and easy to modify. Requires rot protection and regular maintenance.
• Aluminum: lightweight and corrosion resistant, good for modular kits.
• Galvanized steel: strong for heavy snow and wind areas, usually for commercial greenhouses.
• PVC: low cost for small hobby structures, but limited long-term strength.

Glazing options:

• Twin-wall polycarbonate: excellent insulation, diffuses light, and resists hail. A common choice in Arkansas for year-round use.
• Single-pane glass: high light transmission but poor insulation and heavier framing needs.
• Polyethylene film: cheapest and commonly used on hoop houses; replace every few seasons.
• Acrylic panels: good light quality but more expensive.

Foundation options:

• Concrete slab: provides thermal mass and a durable base for benches and equipment. Useful if you will add radiant heat or heavy equipment.
• Perimeter footing with compacted gravel floor: lowers cost and improves drainage. Use treated baseboards to secure the frame.
• Anchored pier footings: good for uneven ground or where frost heave is a concern.

Insulate the foundation perimeter and floor where possible to reduce heat loss in winter.

Ventilation, cooling, and summer strategies

Arkansas summers can be intense. Passive and active cooling are both needed.
Passive ventilation:

• Roof vents and operable side vents allow hot air to escape naturally.
• A ridge vent combined with lower intake vents establishes stack ventilation.

Active cooling:

• Solar or thermostatic roof vent openers for automatic operation.
• Exhaust fans with louvers and intake shutters sized to exchange air 30 to 60 times per hour on hot days for vegetable production.
• Evaporative cooling pads (wet walls) work well in Arkansas where air is humid but still effective when properly sized and maintained.

Shading:

• External shade cloths reduce heat gain without trapping humidity.
• Interior shade paint or retractable shade cloths help control light for delicate crops.

Dehumidification:

• Overly humid summers lead to disease. Use exhaust fans, increased air movement with circulating fans, and dehumidifiers in high-value production areas.

Heating and winterization

While Arkansas winters are generally mild, nights can drop below freezing. Heating maintains growth and prevents crop loss.
Passive heating:

• Thermal mass (water barrels, concrete benches) absorbs daytime heat and releases it at night.
• South-facing glazing and insulating north walls preserve solar gain.

Active heating options:

• Propane or natural gas unit heaters: efficient for off-grid or large greenhouses.
• Electric strip heaters or baseboard heaters: simple and effective for small to medium greenhouses.
• Hydronic radiant heating embedded in concrete slabs or tubing across planting benches provides gentle, even warmth.
• Supplemental heat mats for seedlings and propagation.

Insulation:

• Insulate the north wall and perimeter to reduce heat loss.
• Use bubble wrap or removable polycarbonate sheets for supplemental winter insulation on benches and along the greenhouse perimeter.

Control:

• Thermostats with high-low set points and separate zones for propagation areas help save fuel and maintain stable conditions. Add timers and remote monitoring if available.

Water, irrigation, and soil management

Reliable water is essential. Install a frost-proof exterior spigot or circulate water from barrels warmed by the greenhouse to avoid cold shock.
Irrigation systems that save time and water:

• Drip irrigation with pressure regulation and timers.
• Overhead mist or fog systems for propagation.
• Hand-watering for small-scale setups with moisture sensors to prevent overwatering.

Soil and beds:

• Raised beds with a well-draining, sterilized mix reduce disease.
• Use high-quality compost and balanced fertilizers; year-round production requires steady nutrient replacement.
• Consider hydroponic or ebb-and-flow systems for higher yields in smaller footprints.

Pest management and cultural practices

Greenhouses reduce many outdoor pests but create ideal conditions for others, including aphids, whiteflies, fungus gnats, and fungal diseases.
Prevention:

• Screen vents and doors to exclude insects.
• Sanitize trays, benches, and tools regularly.
• Quarantine new plants before introducing them.

Monitoring and control:

• Sticky yellow cards and regular scouting catch infestations early.
• Biological controls like predatory mites, parasitic wasps, and beneficial nematodes are effective in greenhouse systems.
• Use targeted organic pesticides only when necessary and rotate control methods to avoid resistance.

Cultural controls:

• Maintain proper air circulation with fans to reduce fungal outbreaks.
• Avoid overhead watering on foliage; water at the root zone.
• Keep humidity and temperature within crop-specific ranges.

A practical step-by-step build checklist

1. Confirm site, permits, and utilities.
2. Design the greenhouse: size, orientation, and structural materials.
3. Prepare foundation: level site, pour slab or install footings, and set anchor points.
4. Assemble frame and attach glazing according to manufacturer instructions or plans.
5. Install ventilation and exhaust systems, including thermostats and timers.
6. Set up heating system and any thermal mass elements.
7. Install benches, shelving, irrigation, and electrical outlets with GFCI protection.
8. Test all systems for operation and safety before introducing plants.
9. Add soil, containers, or hydroponic systems and begin phased planting.
10. Implement pest prevention and monitoring routines.

Estimated costs and timeline

Costs vary widely by size and materials.

• Small hobby hoop house (10×12) with polyethylene: $500 to $2,000 and 1 to 3 weekends to assemble.
• Medium twin-wall polycarbonate hobby greenhouse (10×20): $3,000 to $10,000 including foundation, framing, and basic systems; 2 to 4 weeks depending on crew.
• Larger aluminum or steel framed greenhouses with heating and cooling: $15,000 to $50,000+ and several weeks to months including permitting and utility hookups.

Budget for ongoing costs: fuel for heating, electricity for fans and pumps, replacement glazing film, and repairs after storms.

Year-round crop planning and schedules

Plan crops by their temperature and light needs. Use zones inside the greenhouse for warm-season crops (tomatoes, peppers) and cool-season crops (lettuce, kale) simultaneously.
Winter:

• Focus on cool-season greens, root vegetables, and hardy herbs.
• Use row covers or hoop cloches inside the greenhouse for extra frost protection.

Spring:

• Start warm-season transplants early for continuous harvest.
• Gradually vent and acclimate plants to higher light and temperatures.

Summer:

• Shift to heat-tolerant varieties or move sensitive crops to shaded benches.
• Increase ventilation and humidity control to prevent bolting and disease.

Fall:

• Extend harvests of warm-season crops with nighttime heating.
• Plant a second crop of cool-season vegetables as temperatures decline.

Maintenance, record keeping, and safety

Regular maintenance prolongs greenhouse life and protects crops.

• Inspect seals, vents, and glazing monthly and after storms.
• Clean glazing and benches to improve light transmission and reduce disease pressure.
• Maintain heaters, fans, and electrical systems according to manufacturer schedules.
• Keep records of production cycles, pest outbreaks, and environmental set points to refine practices over seasons.

Safety:

• Install smoke and carbon monoxide detectors if using fuel-based heaters.
• Ensure all electrical work meets code and uses GFCI outlets near water.
• Anchor the greenhouse to withstand winds common to your local area.

Final practical tips

Plan for flexibility. Start with a simple structure and upgrade heating, cooling, and automation as your needs and budget grow. Use thermal mass and passive solar design first to minimize operating costs. Build strong foundations and anchors to resist storms and tornado gusts. Finally, start small and scale based on what you learn during your first year of year-round production in Arkansas.