Effect of a high average daily temperature on Anthurium flower formation
What flowers today was determined months ago: the flower and leaf buds of Anthuriums are initiated at the growing point four to six months before they open. When certain
abnormalities appear, we should therefore look back at the climate conditions during that early developmental phase.
Growing Anthuriums for several weeks under hot and humid conditions can sometimes result in flowers developing abnormal shapes months later. We suspect that the newest flower buds are damaged during that warm period and subsequently develop abnormally.
An illustration of the Anthurium growing point is shown below:
It is believed that positions 3 or 4 are sensitive to high average daily temperatures. If the average daily temperature remains above 26–27°C for several consecutive weeks, this effect becomes visible in the flowers four to six months later. A brief period of high temperatures may cause only one deformed flower, but a longer period can result in several flowers on a single plant developing abnormally.
Examples of abnormal flowers:
Examples of abnormal flowers in Asia:
This example shows the climate in the greenhouse of a grower in Asia. An average daily temperature of 27–28°C was maintained in the greenhouse for nine weeks. The graph indicates that from week 26 onwards, the outdoor relative humidity rises from 60% to 70%, reaching 80% in the following week. At the same time, the average daily temperature exceeds 28°C. At that point, the internal climate is no longer optimal: the average daily temperature increases by 3°C, and the average relative humidity in the greenhouse rises to 90%. Due to the high temperature and high relative humidity outside, the pad fan cooling and humidification systems are no longer sufficient to cool the greenhouse effectively.
Under warm and humid outdoor conditions, adiabatic cooling ceases to function effectively. This cooling method relies on dry outside air passing over a wet surface; as water evaporates, it absorbs energy in the form of heat, causing the air temperature to drop and the relative humidity to rise. For this process to work effectively, dry outside air is essential.
Misting in the greenhouse uses the same principle: fine mist evaporates into the air. The transition from liquid to gas requires a large amount of heat, which is drawn from the greenhouse air, lowering the air temperature. But again, this system of adiabatic cooling only works if the relative humidity in the greenhouse is sufficiently low.
After four to five months, the flowers in the grower’s example showed clear abnormalities. It is likely that the high average daily temperatures contributed to this. There is no straightforward solution; the outdoor climate is a decisive factor, as shown in the graph. Mechanical cooling is often too costly. In greenhouses with a movable external screen, temperatures are generally lower than in those with only chalk shading. Optimising nighttime cooling and maintaining good air circulation have both been shown to improve the crop.
