Environmental Conditions:
We saw sunny skies this week and outdoor day time highs in the early 20’s and outdoor nighttime lows in the low-mid teens. This weather has been perfect for growing poinsettias!
The class decided to drop the cooking setpoint from 23C to 21C to slow down the growth rate based on the height measurements that they collected this week.
Day: Heating Setpoint 18C | Cooling Setpoint 21C
Night: Heating Setpoint 18C | Cooling Setpoint 21C
Supplemental Lighting:
Between 6am and 8pm (to give a 14 hour day), if the sensor on the weather station reads less than 400 W/m2 from more than 20 minutes (proof time) then the HPS lights in the greenhouse will turn on.
Hours of Black Out: Not required at this stage of growth. We will start black out in week 41 – that’s next week already!
Nutrient:
EC target is 1.5 – 2.0 pH target is 5.7 – 6.3
EC: The EC’s ranged from 0.4 – 1.6
pH: Many of the pH are concerning low at 4.8. Some are fair in the 5.2-5.7 range. We are starting to see an upturn in pH from last week though. Many cultivars are coming in around 5.0-5.4 pH.
Watering/Fertilizer:
The students assessed soil moisture on Tuesday in our face to face classed and based on our high(ish) EC readings they decided to clear water the poinsettias that required it. In addition to the EC measurements we used the plant heights to guide us towards our decision on what (if anything) we should water with. Our plants are sitting around 22cm already so, we do not need to continue to push them before black out. This gave us the confidence to decide to clear water flush as well. *Remember, we can expect our plants to double in height by the time black out starts.
Observations:
All the poinsettias have been spaced into zones 4 and 5 and the students have started to set up the irrigation drip lines to the plants. We spaced the 4” poinsettias into three (3) flood tables.
We will continue to focus on keeping the humidity around 40%-50% to avoid diseases such as Botrytis, which is common in poinsettias at this stage of growth. Our poinsettia crop continues to have uniform lateral bud break, are growing consistently, have healthy new vegetative growth, developing root systems and are (for the most part) not experiencing many pest or disease pressures. The Alpina cultivar continues to be lagging in growth compared to the other cultivars.
The students measured the poinsettia varieties and on average across the entire crop they are sitting around 22.5cm. This is above average for what we need to plants to be at by the time black out starts (20cm) and the students decided to NOT move up the black out start date but, slow down the growth rate by dropping the day temperature cooling set point to 21C. To clarify, the greenhouses will not start venting once the Argus sensor reads 21C. The decision was determined on the idea that customers will have perceived value by having a larger/taller plant.
Looking forward to next week, we need to start black out on Tuesday! Its important to make decisions/change greenhouse environments early in the week so we can monitor the change and progress. Its not recommended to make changes on Friday when there won’t be any staff in on the weekend to monitor the changes. I anticipate that the poinsettias will be within or slightly taller than our target finished height of 40cm-42cm.