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mheat started grow question 4 years ago
What is a good humidity for autos in flower?
 Lost in the soil!
4 weeks
Lost in the soil! mheat
5 comments · 4 years ago
Week 2
Techniques. Defoliation
CRiSPrGrow answered grow question 4 years ago
well, it's a bit early to say. And there are two answers to that question. First answer is that most growers try to keep the humidity during flower low so that there is less risk of bud rot, that's why you see growers trying to keep it under 50%. However the metabolism of the plant is regulated by VPD. Therefore you want the correct VPD range so the plant grows optimally. The good news is there is a cool company that has made a compromise between keeping humidity low during flower and having the correct VPD range. So the correct humidity depends on the temperature, for temperature between 18 to 20 you want to keep humidity between 30 to 42%. For temperature between 25 to 26 you want to keep humidity between 48-60%. It's complicated but it's correct. hope this helps ! :rocket:
souljasam answered grow question 4 years ago
Check out this graph:

Its called Vapor Pressure Deficit and it determines the optimal humidity at a specific temperature for a specific phase of growth. for example, if you just started flowering you want to follow the green area of the chart. If you are mid-late flower follow the yellow section. Following VPD will allow the plant to transpire properly and have optimal growth.

However, if you don't have really good airflow with fans circulating the air often then you'll wanna go with a lower humidity to prevent bud rot and other molds from forming.
OutForReal answered grow question 4 years ago
Clones and seedling : 70%
Vegetative stage : 40 to 60%
Flowering : 40 to 50%
Late flowering: less than 40%