When To Add Shade Cloth To Louisiana Greenhouses

Louisiana’s climate combines intense summer heat, high humidity, and strong solar radiation. For greenhouse growers, especially those producing high-value vegetables, ornamentals, or young transplants, managing light and temperature is essential to protect plant health and maintain consistent yields. Shade cloth is a simple, cost-effective tool to reduce incoming solar radiation, lower greenhouse temperatures, and improve crop quality–but it must be used at the right times and in the right amounts. This article explains when to add shade cloth in Louisiana greenhouses, how to choose and install it, and how to adjust practices for crop, season, and weather conditions.

Why shade cloth matters in Louisiana

Louisiana summers present multiple environmental stressors that make shading beneficial for many greenhouse operations. The state’s high sun angle during late spring to early fall, combined with extended period of clear sky and intense direct radiation, can push greenhouse air temperatures and leaf temperatures to damaging levels. Plants under heat stress experience slowed growth, flower abortion, sunscald, reduced fruit set and increased water use. High solar radiation also increases vapor pressure deficit and accelerates substrate drying and salt accumulation.
Beyond temperature, excessive light intensity impacts plant morphology and quality. Many greenhouse crops grown for uniformity and marketability–such as tomatoes, lettuce, bedding plants and herbs–benefit from moderated light levels that reduce photoinhibition, leaf burn and uneven coloration. Shade cloth can also help reduce energy costs by lowering the need for forced ventilation or evaporative cooling during peak periods.

Key indicators that you need shade cloth

Knowing exactly when to add shade cloth avoids unnecessary costs and prevents shading crops when they actually need light. Use the following signs and measurements to decide:

Leaf symptoms such as sunscald, bleached or translucent spots, or rapid wilting in the middle of the day.
Repeated daytime air temperatures above 85 to 95 F (29 to 35 C) inside unvented greenhouses for several hours.
Substrate surface temperatures above 110 F (43 C) or leaf surface temperatures that noticeably exceed ambient air temperature.
Flower or fruit drop, poor fruit set, or decreased sugar accumulation during high-radiation periods.
Excessive cooling demand where fans and pads cannot maintain comfortable plant temperatures without high energy or water use.

When during the year to add shade cloth in Louisiana

Timing depends on location (coastal versus northern parishes), greenhouse type (framed glass, polycarbonate, polyethylene film), and crop cycle. General calendar guidance:

Early spring (March to early April): Most crops still benefit from higher light. Temporary light suppression is usually unnecessary unless unseasonal heat spells occur.
Late spring into fall (May through September): This is the primary shading season. Begin evaluating plants by late April and be ready to install shade by mid-May in southern Louisiana and late May to early June in cooler northern locations.
Peak summer (June to August): Shade cloth is often required on most days. Consider higher percent shade or layered shade strategies for the hottest months.
Transitional fall months (September to October): Gradually remove or reduce shade as day length and solar intensity decline, but leave provision for short-term installs during heat waves.
Winter (November to February): Remove or roll back shade to maximize available light for growth and reduce cold trapping of heat if using passive solar. Only retain shade if needed for frost protection strategies that depend on passive heat retention patterns.

Selecting the right shade percentage

Shade cloth is rated by percent reduction in solar radiation. Choosing the correct percentage depends on crop tolerance and greenhouse cooling capacity.

Low light-demand crops (leafy greens, transplants) typically use 30 to 50 percent shade to prevent bolting, reduce leaf scorch and maintain tender growth.
Fruit-bearing crops (tomato, pepper, cucumber) often use 30 to 40 percent shade in full-sun greenhouses; higher shading may reduce fruit quality or yield, so monitor carefully and use adaptive shading during heat waves rather than constant heavy shade.
Ornamentals and shade-tolerant bedding plants can use 40 to 60 percent shade to optimize color and form.
For extreme heat or glass houses that overheat easily, 50 to 70 percent shade cloth may be needed during hottest weeks, applied only when necessary.

Practical approach: start with a moderate 30 to 40 percent shade for most mixed-production operations in Louisiana, then increase in response to persistent high-temperature stress. Consider using dual-layer systems (one permanent moderate layer and one deployable heavier layer) to provide flexibility.

Placement and orientation considerations

Where and how you place shade cloth affects its performance.

Exterior versus interior: Exterior shade cloth reduces solar gain before it enters glazing and keeps glazing surface cooler, which reduces conduction into the greenhouse. Interior shade reduces light inside but is less effective at reducing radiant heat gain through glazing. In Louisiana, exterior installations are generally more effective for temperature control, but interior systems are easier to install and adjust.
East-west versus north-south orientation: For ridge-style greenhouses, use overhead shade that conforms to the roof angle. Consider supplemental side shading on east and west walls where morning and late-afternoon sun generates heat.
Retractable versus fixed: Retractable systems allow dynamic response to daily weather and crop needs. Fixing shade permanently can be easier and cheaper but sacrifices flexibility and winter light.

Installation timing and strategies

Choosing the right time of day and the right strategy reduces plant shock and operational headaches.

Install shade cloth on cool, overcast mornings if possible to avoid trapping midday heat under an interior layer while plants are exposed to direct sun.
Gradually deploy heavier shading during a predicted heat wave rather than abrupt changes that can alter light acclimation.
Combine shade cloth with ventilation, forced air circulation, and evaporative cooling for best effect. Shade reduces heat load, making evaporative pads and fans more efficient.
For mixed crops with different needs, use sectioned shading or movable shade screens to tailor light levels.

Monitoring and adjustment

After installing shade, monitor both microclimate and plant responses and be prepared to adjust.

Use simple handheld thermometers and leaf surface temperature sensors or infrared thermometers to verify reductions. Aim for daytime canopy temperatures in the 75 to 85 F range for many crops.
Watch for unintended consequences: too much shade can elongate stems, reduce flowering and lower yields. Reduce shading or add artificial supplemental light for high-value flower or fruit crops if necessary.
Periodically clean shade cloth and inspect for wind damage; dirty or sagging cloth loses efficiency and can collect moisture that fosters pathogens.

Maintenance, cleaning and seasonal storage

Proper care extends shade cloth life and protects your investment.

Rinse shade cloth annually to remove dust, pollen and algae. Use a mild detergent and low-pressure hose; avoid harsh chemicals and high-pressure washers that damage fibers.
Store removable shade cloth in dry, rodent-proof containers during the off-season. Fold loosely to avoid stress lines in fabric.
Inspect seams, grommets and attachment points before the shade season. Replace worn ties or fasteners. For exterior installations verify wind bracing and consider quick-release anchors to avoid severe damage in storms.

Crop-specific recommendations for Louisiana growers

Tomato and pepper: Use 30 percent shade when outside air temperatures routinely exceed 85 F for several hours. For heat waves, add a temporary 40 percent layer on the roof and side vents in the hottest hours only. Avoid continuous >50 percent shading or yields may drop.
Leafy greens and herbs: 30 to 50 percent shade improves leaf quality and reduces bolting; in southern parishes start shading earlier in spring and continue later into fall.
Ornamentals and bedding plants: 40 to 60 percent shade preferred for many species; use higher shading during propagation to prevent etiolation but maintain light enough for compactness.
Seedlings and plugs: Moderate shade (30 to 40 percent) combined with high humidity and lower temperatures yields sturdy seedlings. Avoid placing tender seedlings in direct midday sun even in spring.

Common mistakes and how to avoid them

Installing shade too early: This can reduce growth and slow crop development. Use temperature and light monitoring rather than calendar alone.
Over-shading fruit crops: Monitor flowering and fruit set and use temporary, not permanent, heavy shading.
Ignoring air movement: Shade reduces solar load but must be paired with adequate ventilation. Keep horizontal airflow fans running to prevent microclimates that favor diseases.
Neglecting maintenance: Dirty, torn or improperly stored shade cloth shortens lifespan and reduces efficiency.

Practical checklist for deciding to add shade cloth

Measure interior daytime maximum and minimum air temperature for several days. If maximums exceed crop-specific thresholds (commonly 85 to 95 F), prepare shade.
Inspect leaf surface and fruit for signs of sunscald or bleaching.
Note trends in substrate evaporation and irrigation frequency; sharp increases indicate higher radiation stress.
Review weather forecasts for multi-day heat waves and plan to deploy heavier shade during those windows.
Match shade percentage to crop tolerance and greenhouse heat gain; start moderate and increase only when plant signs or climate data justify it.

Conclusion and takeaways

Shade cloth is an essential tool for Louisiana greenhouse operations when used thoughtfully. The right timing–typically late spring through early fall–combined with appropriate shade percentage, exterior placement, and integration with ventilation and cooling systems will protect plants from heat damage, improve quality and reduce energy and water costs. Monitor both environmental data and plant condition, use retractable or layered systems for flexibility, and maintain the fabric to maximize its lifespan. With these practical guidelines, growers in Louisiana can make confident, crop-specific decisions about when to add shade cloth to their greenhouses.