Week Number: 39
Environmental Conditions:
Wow! Week 39 already! Rain and sunshine replaced the smoky skies from last week, thankfully! We saw outdoor day time highs in the early 20’s and outdoor nighttime lows in the low-mid teens this week.
The class decided to drop the cooking setpoint from 24C to 23C to slow down the growth rate based on the height measurements that they collected this week.
Day: Heating Setpoint 18C | Cooling Setpoint 23C
Night: Heating Setpoint 18C | Cooling Setpoint 23C
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.
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 again this week.
pH: Many of the pH are concerning low at 4.8. Some are fair in the 5.2-5.7 range.
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 20cm 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:
This week we spaced the poinsettias because the new vegetative growth is touching – which is an indicator that we use. Spacing the poinsettias will encourage outward growth because the lateral buds now have space to grow into, instead of being forced upwards when they were pot to pot.
In early growth stages, weeks 33-39, we were focused on keeping the humidity around 60%-70% to avoid desiccation of newly pinched plants and even unfurling of new leaves. HOWEVER, now humidity is the enemy! Our plants are established at this point and we are preparing ourselves for black out in week 41 which will result in promoting generative (flowering) growth. We will 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. Worth noting that the Alpina cultivar is not doing as well as the other cultivars, likely due to the fungus gnat pressure they are experiencing. This week we destroyed a couple of Alpina plants to get at the roots and determined there are sign of Pythium in the cultivar as well.
The students have been taking height measurements weekly and based on our taller than average (for this stage of production) they decided to drop the cooling temperature to 23C to slow the plants growth down. It’s important to remember that have to be vigilant in our crop monitoring so that we have the flexibility to made gradual adjustments to the environment and avoid extreme fluctuations of temperature, humidity, fertilizer or pest pressures. It’s essential that all students are measuring the poinsettias using the same techniques so that we have reliable data to make our decisions from.