1. Control Excessive Greenhouse Heat

A greenhouse can become significantly warmer than the outdoor environment during a sunny August afternoon. Prolonged heat can cause blossom drop, leaf scorch, poor pollination, slowed growth, and reduced fruit quality.

Use a combination of shading, ventilation, and air circulation rather than relying on only one cooling method.

• Install shade cloth: A properly selected exterior shade cloth can reduce solar heat gain before sunlight enters the greenhouse. The ideal shade percentage depends on the crop, greenhouse glazing, and local climate.
• Open roof and sidewall vents early: Begin releasing accumulated heat before the greenhouse reaches stressful temperatures.
• Operate circulation and exhaust fans: Consistent airflow helps reduce hot spots, strengthen plants, and move warm air out of the structure.
• Use evaporative cooling when appropriate: Fan-and-pad systems can provide effective cooling in suitable climates when correctly sized and maintained.
• Monitor temperatures at plant level: Place sensors near the crop canopy rather than directly beside a vent, fan, or sunny wall.

2. Adjust Watering and Humidity

Plants generally use more water during hot, bright weather, but overwatering can still lead to root disease, nutrient loss, fruit cracking, and excessive humidity.

• Water early in the day so plants are hydrated before peak afternoon heat.
• Check containers individually. Small pots and hanging baskets may dry out faster than raised beds or large planters.
• Apply water directly to the root zone whenever possible instead of routinely wetting the foliage.
• Use drip irrigation or automatic watering systems to improve consistency and reduce wasted water.
• Inspect irrigation lines and emitters for clogs, leaks, and uneven flow.
• Provide drainage so excess water does not collect around roots or on the greenhouse floor.

3. Start Fall and Winter Crops

August is not simply the end of summer production. It is also an important planting period for crops that prefer the milder temperatures and shorter days of fall.

Suitable planting dates vary by region, greenhouse temperature, and expected first-frost date. Review local recommendations before selecting varieties and sowing dates.

Vegetables to Consider

• Lettuce and salad mixes
• Spinach
• Kale
• Swiss chard
• Arugula
• Pak choi and other Asian greens
• Radishes
• Green onions
• Cilantro, parsley, and dill

Broccoli, cauliflower, cabbage, and Brussels sprouts may also be started in trays for later transplanting, depending on your location and production schedule.

4. Manage Tomatoes, Peppers, and Cucumbers

August is often the peak harvest period for warm-season greenhouse crops. Consistent harvesting and plant maintenance help direct energy toward healthy fruit development.

• Harvest frequently: Pick cucumbers, peppers, and tomatoes regularly to maintain quality and encourage continued production.
• Support heavy plants: Check tomato clips, trellis strings, stakes, and crop-support systems.
• Remove damaged foliage: Prune yellow, diseased, or heavily shaded lower leaves while avoiding excessive defoliation.
• Maintain balanced nutrition: Follow a crop-specific fertility program and avoid overapplying fertilizer.
• Improve pollination: Good airflow and moderate temperatures support pollination. Excessive heat may cause blossoms to drop before fruit develops.
• Inspect fruit daily: Remove split, damaged, or overripe produce before it attracts pests or develops disease.

5. Watch for Whiteflies, Aphids, and Spider Mites

Warm greenhouse conditions can support rapid pest reproduction. Whiteflies, aphids, thrips, fungus gnats, and spider mites may become established before visible plant damage becomes severe.

• Inspect the undersides of leaves, new growth, flowers, and growing points several times each week.
• Use yellow or blue monitoring cards as appropriate to identify flying pest activity.
• Isolate new plants before introducing them into the main growing area.
• Remove heavily infested or diseased plant material and dispose of it away from the greenhouse.
• Control weeds inside and immediately around the greenhouse because they may shelter pests and plant diseases.
• Use biological controls or labeled treatment products according to the crop, pest, and product instructions.

6. Complete August Greenhouse Maintenance

Small maintenance tasks completed now can improve plant health and reduce problems during the transition into fall.

Prepare Today for a Productive Fall

August is a month of transition. Summer crops may still be producing heavily, but shorter days and cooler nights are approaching.

By maintaining shade, ventilation, irrigation, sanitation, and pest monitoring—and by starting cool-season crops at the appropriate time—you can carry greenhouse production smoothly from late summer into fall.

Every greenhouse and climate is different. Adjust your management practices according to your crops, structure, glazing material, ventilation system, and local weather conditions.