Plant was showing signs of nutrient burn on the leaf tips. Discontinued nutrients. Adding 6.2 pH water only through the dripper. I will most likely not add any more nutrients for the duration. There has been little height growth so I assume the plant is in full flower now. I switched the overhead lights to red only. Still using two full spectrum gooseneck lamps as well. The overhead lights were lowered. Overall, I want the plants to receive plenty of light, but I also want the temperature in the 75 degree range with lights on. The light schedule was switched to 12 hours. Turning off the blue light has brought the temps in the grow room down from about 80 degrees to about 75 degrees. Humidity in the room was brought down to 45% until harvest. Even though this is an auto-flower, the goal is to get the best conditions for the buds to fatten up now.
Just like at the beginning of every week, the plant was rotated 90 degrees clockwise to ensure even light on the plant. The plant is looking good. the buds are still immature and the pistils are still mostly white. The trichomes are turning milky. I think there is still three more weeks until harvest.
By mid week soil was a little too moist. Dripper frequency was increased from 30 seconds every 4 hours to 30 seconds every 6 hours. Leaves are starting to yellow a little bit on the bottom. Removed some yellow leaves. Buds look good. Flushing with water at 6.2 pH and 17 ppm total dissolved solids. No more nutrients will be added until harvest. Focus is solely on bud growth now.
End of week: The leaves on the bottom are starting to yellow. They will be removed as they turn color. Probably not much I can do about the nutrient burn. The miracle grow soil I used has time released nutrients (nitrogen). It is a race between the leaf damage and bud growth now. I don't anticipate it causing any problems. The buds should mature well before the leaves get too damaged. The next grow in this soil should do much better once the nutrients in the soil are used up. Still looking at 1 to two weeks until harvest.
Grow Room
The grow room is made from ¾” Schedule 40 PVC Pipe frame. Corrugated cardboard boxes lined with black duct tape on the outside and Vivosun Horticulture Highly Reflective Mylar Film (Roll 4’ X 50’ 2 Mil for $32) inside adhered to the cardboard with two-sided carpet tape. The cardboard panels were mounted to the frame using zip ties. Reflective mylar was also placed on the floor of the room. There are two shower curtains hung on front with a white shower curtain facing inside and a black shower curtain to the outside. The white shower curtain should reflect some light back into the room with the black shower curtain absorbing any light getting through the white curtain. It is literally PVC pipe, cardboard, duct tape, wire ties, and a couple shower curtains. Since the room is in a dark unfinished basement it is open at the top (about 1 ft head space to ceiling). This should allow for adequate ventilation without the need for separate exhaust. See the Air/ Temperature Control section. The room is 4’ x 6’ but can be easily expanded with little investment. The room cost about $70 to build. It can be expanded to 12’ x 4’ for an additional $20.
Moisture Control and Watering
Humidity in the room is controlled by a Vremi 3,000 Sq. Ft. Dehumidifier ($280) for the 700 Sq. Ft basement where the grow area is located. The dehumidifier sits just outside the grow room. A Moistenland Automatic Drip Irrigation System ($48) is fed directly from the dehumidifier reservoir. Both duration and interval of watering is controlled. The ¼” dripper line feeds through the wall of the grow room. The moisture collected out of the air is used to automatically water the plants. No other water source is used. The water from the dehumidifier is about 6.1 pH with 65 ppm total dissolved solids (before nutrients). Nutrients are added directly to the dehumidifier reservoir each week as required. The dehumidifier is thoroughly cleaned and sanitized between each grow… including the filters. See Air/ Temperature Control for how mold and bacteria are controlled.
Air/ Temperature Control
The grow area is in a 700 sq ft unfinished basement. The home HVAC system is also in this space. The temperature remains consistent between 70 and 75 deg F. (21-24 deg C.) outside the grow room. Inside the grow room remains between 70 to 80 deg F (21-27 deg C.) depending on the time of day and whether the lights are running. There is about an 8-degree difference between lights on and lights off. There is no need for extra temperature controls. There is a Pure Enrichment PureZone Air Purifier - True HEPA Filter ($100) with a 3-stage filter that includes activated charcoal to reduce odors. The filter is rated for 200 sq ft so it should be enough for the 24 sq ft in the grow room. The air purifier is placed on the floor. It brings in air from the grow room blowing the filtered air up from the top of the unit. The fan in the purifier is set on high and expected to be the only thing needed to move air, eliminate mold and bacteria, and provide odor control in the room. The air purification filter is changed out for each grow. Again, the top of the grow room is open, so ventilation should not be a problem. I have a coffee can with hole punch in the lid Ona Gel Pro inside to help control oder along with a Earth Care Janitorial and Industrial Odor remover hung inside the room.
Lighting
The 6’ x 4’ grow room has 2 WHOSLED LED 1200W (230w actual) Dual Switch Dual Chip Plant Lamps ($110 ea) attached to floor joists above the room with a nylon rope. They have blue, red, and full spectrum settings. They can be easily adjusted for height. There are also 2 Relassy 200w (45w actual) Full Spectrum Grow Lamp, Dual Head Gooseneck Plant Lights ($30 ea) used. Put another way, there are 4 100w full spectrum LED that can direct light as needed under the plant canopy. All lights are connected to a timer. Light cycle matches natural day/ night cycle.
Soil and Planting
The first grow with this setup is 3 autoflower plants (Bubblegum, Jack Herer, and OG Kush). A 6’ x 4’ grow room is plenty of room for 3 plants. They are planted in JERIA 7 Gallon, Plant Grow Bags (12 for $26) with Hydrofarm 14” plant saucers (10 for $41) under them. The soil is a 50/50 mix of Miracle Grow Potting Soil and Miracle Grow Garden Soil. About 2 oz of Summit Mosquito Bits - Quick Kill (30 oz for $17) was incorporated into the top 3 inches of soil in each grow bag. This should control gnats and other soilborne insects. Plants were started in rapid rooter and seedling trays for the first 10 days before being transplanted directly to the 7 gallon grow bags.
Monitoring Grow Conditions
There are several parameters being monitored during the grow. Soil moisture and light are measured using a Kensizer Soil Tester ($14). The soil mixture used is known to have a 6.5 pH so the water pH is monitored using a Vivosun High Accuracy Pen Type pH Meter ($10). A General Hydroponics pH test kit ($23 includes pH Up and pH Down) is also used for the water pH to ensure accuracy. A Vivosun TDS sensor ($10) is also used on the water. Temperature and humidity inside the grow room are monitored using a Govee Indoor Temperature Humidity Sensor with Bluetooth ($13).
Nutrients
The watering schedule is about 12 oz per day per plant. It will fluctuate between 10 and 15 oz per day depending on soil moisture measurements. For 3 plants that comes out to about 2 gallons per week. Since the fresh soil mixture already has nutrients, the liquid nutrients are added directly to the dehumidifier reservoir once per week at about ¼ recommended strength. Fox Farm Big Bloom, Grow Big, and Tiger Bloom are used per the ratios recommended for growth stage. Used the Fox Farm Feeding Schedule as a guide (1/4 of recommended amount).
Overall Comments
There should be good control on grow room temperature and humidity. There is probably enough light for a grow room twice the size… or twice the plants using about 2800w LED total (600w actual usage). Light leaks are naturally controlled by being in a basement room with no windows and light schedule follows actual day/ night hours (the first grow is all autoflower anyway). The air in the room is purified with good ventilation. Watering is fully automatic with proper pH water and nutrients are added per schedule. The soil is the proper pH starting out in is protected against insects.
Grow room temperature and humidity is continuously monitored and charted via Bluetooth. Soil moisture is monitored daily and controlled through automated dripper settings. Light intensity is monitored and controlled via adjustable lighting. Water pH is measured daily using a probe and titrated weekly to verify accuracy. Total dissolved solids in the water with nutrients is measured daily. The grow journals for each plant can be found here.