Question 1

1. What happens if your VPD is too high?

Accepted Answer

When vapor pressure deficit (VPD) is too high, plants lose water through transpiration faster than their roots can replace it. This can cause wilting, leaf stress, reduced growth, and stomata closing, which limits photosynthesis.

Question 2

2. Does VPD matter at night?

Accepted Answer

Yes, VPD matters at night because plants continue to exchange moisture with the surrounding air, even when transpiration is generally lower. Maintaining a suitable nighttime VPD helps manage plant water balance and reduce problems associated with excessive humidity.

Question 3

3. Is 1.3 VPD good for flowering stage?

Accepted Answer

A VPD of 1.3 kPa can be suitable for some flowering plants, but the ideal level depends on the crop, growth stage, temperature, and growing conditions. Check crop-specific recommendations before using this value as a target.

Question 4

4. What is a good VPD number?

Accepted Answer

A VPD between approximately 0.8 and 1.2 kPa is a common starting range for many actively growing greenhouse plants. However, the best target varies with plant species, growth stage, temperature, and environmental conditions.

Question 5

5. What is the best VPD for early flowering plants?

Accepted Answer

Many greenhouse crops do well around 0.8–1.2 kPa during early flowering, although some require a different range. Adjust VPD according to the specific crop and monitor leaf condition, temperature, and moisture levels to avoid unnecessary stress.

Question 6

6. Is VPD more important than humidity?

Accepted Answer

VPD often provides more useful information than relative humidity alone because it accounts for both air temperature and moisture levels. However, neither replaces the other: effective plant management considers VPD, humidity, temperature, airflow, and root-zone moisture together.

Plant Growing

VPD Calculator Check Vapor Pressure Deficit for Plant Growth