Grow Diary Granddaddy Purple

Granddaddy Purple - Week #5 of Flower (Mid Flower)

This week was marked by a notable shift in environmental conditions as an unseasonably warm and humid air mass moved into the area. To maintain a stable grow environment, I deployed a portable AC unit outside the tent in dry mode. This allowed cooler, drier air to be pulled into the tent whenever the exhaust system activated due to temperature or humidity increases. This approach proved effective at stabilizing conditions without introducing excessive cooling directly into the canopy.

During lights on, temperatures averaged around 75°F with relative humidity near 53%, maintaining a VPD in the 1.3–1.5 range, occasionally reaching 1.6 later in the light cycle. During lights off, temperatures dropped to roughly 65°F with relative humidity settling in the mid-40s to low-50s, keeping VPD between 1.0 and 1.3. Root zone temperatures were closely monitored and are now stable between 62 and 63°F. Nutrient solution temperature has consistently remained between 62–63°F as well.

Bud development continues to accelerate. The plants remain firmly in mid-flower, with pistils still fully extended and colas maintaining a pointed structure rather than rounding or swelling prematurely. Trichomes remain mostly clear with only early signs of clouding, indicating the plants are still in an active growth and stacking phase. Bud weight is increasing steadily, and additional structural support will likely be required in the coming weeks. Aroma production has intensified significantly, with a strong blend of skunk and sweet citrus now overpowering the carbon filter at times.

Lighting intensity was increased this week, with PPFD raised from approximately 950 to 1050 and DLI increasing from roughly 41 to 45–46. UVA exposure was also extended from 120 to 150 minutes per day. The plants responded well with no signs of stress. Feeding continued on a consistent schedule of once every 48 hours, with each plant receiving 1–1.25 gallons of nutrient solution per feeding. The solution was maintained at a pH of 6.1 with a medium-strength nutrient mix measuring approximately 850–900 ppm. Silica was applied once this week at 1 ml per gallon, and Cal-Mag was included at 5 ml per gallon.

Earlier in the week, I observed mild potassium uptake issues on a few larger fan leaves. Investigation revealed that root zone temperatures had dipped to approximately 56–58°F due to cool air entering near the base of the tent through the side vents. To correct this, I installed a baffle system around the pots to redirect incoming air toward the heater before reaching the containers. Since making this adjustment, root zone temperatures have stabilized at 62–63°F, and no further progression of the deficiency has been observed. This correction should allow nutrient uptake to normalize going forward.