All plants require different humidity levels for their growth cycle. In general, indoor plants require relative humidity to be maintained
between 60 and 85%, but all of them have their own preferences.
Leafy greens should have a 50 to 70% RH to avoid edge burn, root rot,
powdery mildew and other diseases.
On the other hand, tomatoes’ humidity needs can vary between 60 and 85% RH, with 70% RH being the optimal level
for pollination.
As for cucumbers, they require 60-70% RH.
However, humidity needs for all vegetables vary between day and night – cucumbers, for example, require 70-90% RH at night. This is when a reliable and easily programmable humidifier can come in handy.