2Hearts
Well-Known Member
Its winter here now and gosh its getting cold. One thing ive noticed since those humid warm days of summer is a total plumet in relative humidity and especially so in my 75°f/24°c veg box.
Being new to Vapour Pressure Deficiet i soon discovered that low humidity and high temps closed leaf stoma causing low transpiration and transport of phosphorous, calcium and sulfur. This could be why my summer greens are now winter purples with slight wilt and yellowing.
Cranking the humidifier to 75% soon made my plants summer greens again. Damn humidity makes a plant sensitive.
Vapour pressure deficiet is (as far as i understand) is the difference in pressure between the 100% saturated leaf stoma and the outside air pressure aroud the leaf in my veg box. The scale is in milibars kinda like the high and low pressure weather systems on the news. Ideally marijuana and a lot of other plants like the pressure difference to be 8-9 milibars. 75°f at 70% humidity seems to be in that region and what seems to be best for my seedlings and veg box.
Lower temps mean lower relative humidity i.e. growing at 65°f with 60%humidity would also be in the sweet spot as 85°f with90°humidity is also. I guess its why some plants can grow in hotter temps if the humidities right.
The reason to push temps as it would also be to push light is that more heat and light make photosynthesis happen at a greater rate. The limiting factor would be co2.
To acuratley gain my veg boxs humidity reading i place my hygrometer at canopy level with my thermometer. The thermometer is unshaded from the light but my hygrometer has a roof that shades it from the light. Hygrometers need shading as straight under the light 50%humidity reads as under 30% humidity.
I like and now strive to keep my veg box at 75°f and 70% humidity which gives me least problems.
I read on a lot and saw that outside the vapour pressure deficiet values and especially low humidity in veg can cause stoma to close depriving the plant and lowering transpiration rates. The main nutrients that are effected by transpiration, through the xylem, are phosphorous calcium and sulfur. Guess the lack of phosphorous is the reason behind those purple stems and calcium and sulfer deficiencies basically wreak havoc at those grow sights and new leaves. I find low humidity causes me watering problems but with the correct temps and humidity i have none.
Finally all modern greenhouses seem to use vapour pressure deficiets to control and work out everything from watering to fertilizing. My plants see unprecedented growth at 75°f and 70%rh so much so that its become a marker for my veg box.
One thought i had that countered this was that afghanistan thailand and mexico were pretty dry low humidity places but soon discovered the best weed comes from deep in humid warm valleys not from deserts or atop of a mountain range, like the kush valley which i bet smells amazing in summer.
Being new to Vapour Pressure Deficiet i soon discovered that low humidity and high temps closed leaf stoma causing low transpiration and transport of phosphorous, calcium and sulfur. This could be why my summer greens are now winter purples with slight wilt and yellowing.
Cranking the humidifier to 75% soon made my plants summer greens again. Damn humidity makes a plant sensitive.
Vapour pressure deficiet is (as far as i understand) is the difference in pressure between the 100% saturated leaf stoma and the outside air pressure aroud the leaf in my veg box. The scale is in milibars kinda like the high and low pressure weather systems on the news. Ideally marijuana and a lot of other plants like the pressure difference to be 8-9 milibars. 75°f at 70% humidity seems to be in that region and what seems to be best for my seedlings and veg box.
Lower temps mean lower relative humidity i.e. growing at 65°f with 60%humidity would also be in the sweet spot as 85°f with90°humidity is also. I guess its why some plants can grow in hotter temps if the humidities right.
The reason to push temps as it would also be to push light is that more heat and light make photosynthesis happen at a greater rate. The limiting factor would be co2.
To acuratley gain my veg boxs humidity reading i place my hygrometer at canopy level with my thermometer. The thermometer is unshaded from the light but my hygrometer has a roof that shades it from the light. Hygrometers need shading as straight under the light 50%humidity reads as under 30% humidity.
I like and now strive to keep my veg box at 75°f and 70% humidity which gives me least problems.
I read on a lot and saw that outside the vapour pressure deficiet values and especially low humidity in veg can cause stoma to close depriving the plant and lowering transpiration rates. The main nutrients that are effected by transpiration, through the xylem, are phosphorous calcium and sulfur. Guess the lack of phosphorous is the reason behind those purple stems and calcium and sulfer deficiencies basically wreak havoc at those grow sights and new leaves. I find low humidity causes me watering problems but with the correct temps and humidity i have none.
Finally all modern greenhouses seem to use vapour pressure deficiets to control and work out everything from watering to fertilizing. My plants see unprecedented growth at 75°f and 70%rh so much so that its become a marker for my veg box.
One thought i had that countered this was that afghanistan thailand and mexico were pretty dry low humidity places but soon discovered the best weed comes from deep in humid warm valleys not from deserts or atop of a mountain range, like the kush valley which i bet smells amazing in summer.
