2023 Guide to Cannabis Production - 20

CLIMATE CONTROL
Climate
Optimization
A healthy, consistent cannabis crop relies on
precisely managing temperature and humidity.
By Abby McGarry
I
ndoor cultivation has several advantages when it comes
to cannabis production, but, at a broad level, the No. 1
advantage is the ability to manipulate the environment.
GPN reached out to Brandy Keen, co-founder and senior
technical advisor at Surna Cultivation Technologies, to talk
about the role climate plays in perfecting the outcome of the
harvest. Here, she tackles setting temperature and humidity
targets, the role of automation, and prioritizing investments.
GPN: Climate is one of the main reasons to grow indoors,
but there's a lot that goes into creating an ideal climate. Can
you talk about the importance of climate management and
the impact on the crop?
Brandy Keen: At a high level, the importance of effectively
managing the climate for a cultivation facility cannot be
overstated. Temperature and humidity affect quality and
yields, both as independent variables and in conjunction
with each other as it relates to vapor pressure deficit (VPD)
and managing transpiration rates. From a general plant health
standpoint, excessively high or low temperatures, excessively
high or low humidity, inconsistent conditions, and excessively
high or low VPD can all cause reductions in yield, negative
effects on quality, or complete crop loss. Even if the climate
issues seem minor or insignificant, they can weaken the
plant's natural defenses and make them more susceptible to
damage from other external stressors such as pests or fungus.
Reductions in transpiration caused by high humidity can
lead to mold and rot, and excessively high transpiration
can lead to lowered yields, nutrient lock, and unfavorable
quality. Excessively high temperatures can cause stretching
or hermaphroditism. Excessively low, high, or inconsistent
temperature or inconsistent humidity can make the plant
more susceptible to powdery mildew, and the list goes on
and on.
GPN: What's the ideal temperature and humidity for a
cannabis crop, and what tips do you have for reaching the
correct temperature and humidity balance?
Keen: This is a subject of much debate and there are
several factors that will influence the " ideal " temperature
and humidity. In general, most cultivators target a lightson
temperature for flowering plants of 75 to 84° F and 45 to
20 2023 GUIDE TO CANNABIS PRODUCTION
65% relative humidity (RH). Lights off is usually 65 to 75° F
and 45% to 65% RH. Most cultivators start a little warmer
and more humid at the beginning of the flowering cycle
and gradually bring temperature and humidity down as
the plant matures into late flower. However, these are just
rules of thumb and we've seen a number of deviations from
these ranges - every cultivator will develop his or her own
climate recipe. Temperature and humidity are important as
isolated variables, but the way they work together to achieve
a specific vapor pressure deficit is also important.
Equally important is the dewpoint temperature and its
influence on the ability for the climate control system to
effectively manage humidity, which is also a product of
both temperature and humidity. The best advice we can
offer is to work with an HVAC/D designer who understands
what you're trying to achieve and be as detailed as possible
when you discuss your irrigation strategies and volumes,
and temperature and humidity targets, over the life cycle of
the plant, to ensure that the end design meets your needs.
Understand also that the HVAC/D system infrastructure
is going to have limitations. If you provide one set of
design parameters during the facility design, that's what
the infrastructure will be designed to support, and if you
deviate from those parameters in operation, you will likely
struggle to achieve the temperature and humidity targets.
GPN: What are some of the mistakes you see growers
making when it comes to greenhouse climate?
Keen: Underestimating how much they'll have to spend
on climate control if they are looking for tight parameters
in geographies that don't have a perfect cannabis climate
is one mistake we see. Even relying on ventilation as a
primary means of control and being flexible on temperature
targets, the cost of heating in cold climates, and maintaining
humidity in almost any climate, is often shocking to
cultivators who think they're going to build a greenhouse
without significant investment.
Many cannabis growers are used to having mechanical
cooling and dehumidification to achieve their desired
temperature and humidity in indoor warehouse
grows. However, most greenhouses use ventilation and
2023 Guide to Cannabis Production

Table of Contents for the Digital Edition of 2023 Guide to Cannabis Production
