Plant Growth Regulators and Greenhouse Climate: What Growers Should Consider

A crop’s response to a plant growth regulator can be influenced by its development stage and growing environment. Light, temperature, humidity, root-zone conditions and nutrition all affect plant growth. They do not create a universal formula for changing a PGR rate.

Light and temperature

Light level and photoperiod shape crop growth and development. Temperature affects plant metabolism and can influence how a crop responds to an application. The relevant limits and timing depend on the product and crop; follow the label rather than increasing or reducing a rate based on general rules.

Humidity and leaf wetness

Humidity, air movement and leaf wetness influence the greenhouse microclimate and may affect spray drying or crop stress. Application requirements vary by formulation and method. Check product directions and avoid spraying stressed plants or under conditions that the label identifies as unsuitable.

Fertigation and nutrient balance

Fertigation supports crop growth by supplying water and nutrients. It does not substitute for a PGR, and a PGR cannot correct a nutrient deficiency. Maintain a crop-appropriate nutrient program and check compatibility before combining any products. Do not add a PGR to a recirculating nutrient solution unless that application is specifically permitted by its label.

A practical record-keeping routine

• Record crop, cultivar, growth stage and recent management.
• Note temperature, light and humidity conditions around the intended application.
• Record the product, label rate, application method and any required restrictions.
• Observe the crop response and keep the results tied to the exact product and conditions.

Greenhouse monitoring can make crop conditions easier to understand, but application decisions must remain within the product label and local rules.