Propagation/Greenhouse Management
Part 1 – 108 | Unit 1.3
Lecture 2: Managing Environmental Conditions
c) Air circulated by manual control of inlet and outlet venting; complements the heating
and cooling capacity of passive solar design
d) Moisture regulation/delivery managed by the grower through manual/hand delivery,
semi-automated, or automated delivery systems
e) Microclimatic heating may be possible; offers additional environmental control when
power is available to supply the system, but this goes beyond the purely passive
- Enclosed (semi) Automated Greenhouses: Precise environmental control achievable via
active mechanisms:
a) Characterized by ability to fully close growing environment, regulate temperatures/air
circulation through passive and active venting and fan-driven air movement, heating/
cooling by fans, furnaces, swamp coolers, etc. (see Lecture 3 for details)
b) The interplay of environmental conditions and sophistication of active management
tools dictate the precision of environmental control: More precise control comes with
more responsive systems and lesser extremes in conditions to be regulated
c) Trapped solar radiation works in concert with active heating mechanisms to create
desired warmth
d) Cooling via passive venting systems works in concert with active cooling mechanisms to
create desired temperatures
e) Microclimatic heating in root zone via hot water pipes or electric cables is often used to
optimize conditions and speed the rate of plant growth
f) Automated or manually controlled sprinkler systems are the norm in more actively
managed and infrastructure-intensive greenhouses, but spot watering by hand remains
critical to optimize plant health
- Open Hoop Houses/Quonset Huts: Can partially modify environmental conditions and
improve plant health, especially in milder climates
a) Temperature modification: Umbrella-like coverage creates slightly warmer day and
night conditions, which favors more rapid development than possible outdoors
b) Provide some buffering against effects of wind, though air circulation may be limited
by how structure is located relative to prevailing winds, nearby windbreaks, and other
structures, unless the hoop house is outfitted with roll up or roll down sides and end
wall venting
c) Grower controls moisture regulation, delivering necessary irrigation through same
means as in greenhouses
d) Can be used as an intermediate step between greenhouse and outdoors: Greater
exposure of plants to wind and day-night temperature fluctuations offers a gradual step
in the hardening off process, especially when the favorable conditions created in the
greenhouse are dramatically different than prevailing outdoor conditions
- Germination Chambers: Small-scale, self-contained facilities that provide optimal control
over temperature and humidity to facilitate rapid, high-percentage germination
a) Whether pre-assembled or home made, chambers are comprised of a water-holding
pan, a submersible heat source with variable temperature control, a water supply,
insulated walls, suitable shelving to hold propagation trays, and doors large enough to
easily move containers in and out of the chamber. Units usually hold between 24–48
propagation trays but can be designed larger or smaller to meet needs.
b) Together, these elements create an energy efficient, very consistent environment for
germination where humidity and temperature can be optimized to greatly improve and
speed germination