Cutting Environment

Question 1

Artificial Leaf (screen balance)

Answer 1

Artificial leaves are also 
called screen balances. 
The screen is wet by 
misting and dries in a 
similar pattern to the 
cutting’s leaf. 
The screen is on a fulcrum 
that tips to trigger 
misting as it dries.

Question 2

Bottom Heat

Answer 2

Heated water under the bench
Placing heat pipes under the bench is an efficient way to provide
bottom heat to cuttings while heating the greenhouse.

Heated air under the bench- not as efficient but cheaper

Heated water on top of the bench 
An efficient root zone heating 
method is using re-circulating hot 
water that flows tubing on the 
bench top. 

Heated water under the greenhouse floor 
Large growers place 
permanent hot water 
tubes in the greenhouse 
floor. 

PVC pipes lined-up
under propagation beds.
Sand or gravel will be
placed over the pipes.

Question 3

Electronic Leaf

Answer 3

An electronic leaf is a
device that estimates the
water content on a leaf
surface.

Electrodes in the probe 
complete an electronic 
surface when wet. As it 
dries out, it signals the 
solenoid to trigger mist.

Question 4

Ellepots

Answer 4

Made from Sweden. It is a sustainable way to add whatever medium you like into a biodegradable container rather than a petroleum container.

Question 5

Enclosed systems for rooting

Answer 5

Increases humidity. One of the principles to reduce water loss in cuttings. Cold or hot frames. Polyethylene tents. Contact Sheets.

Question 6

Evapotranspiration

Answer 6

Evapotranspiration
is water loss from the plant
plus the container medium.

Question 7

Fogging Systems

Answer 7

Fog maintains the air and leaf VPD at near
equilibrium to prevent water loss from the leaf. Fog is generated by forcing air through water emitted by a rapidly circulating nozzle or jet. The point is not to get wet since the particles are so tiny.
(2-40 microns)

Question 8

Intermittent Mist

Answer 8

Provide water to the leaf surface. One of the principles to reduce water loss in cuttings. This can easily cause foilar disease.
(more than 50 microns)

Water is deposited on the
leaf surface due to misting.

It evaporates as the leaf is 
heated by the sun and 
substitutes for water that 
would have been lost from 
the leaf.

Question 9

Light radiance and rooting

Answer 9

1. Cuttings do not have
   significant photosynthesis
   until roots have formed.
2. High light levels lead to
   higher leaf temperature and
   increased transpiration.

Light irradiance does not need to be high during
cutting propagation.

Adequate initial light levels are between:

600 to 1000 foot candles

120 to 200 mol / M2 / sec.

After initial rooting

1000 to 2500 foot candles

200 to 500 mol / M2 / sec.

Question 10

Mist nozzles

Answer 10

Mist systems use nozzles that have droplets that are greater than
50 microns in size. The two main nozzle types are pressure jets,
whirl-type and deflection nozzles.

The best pressure jet nozzles, have low water output, work under
low water pressure and do not drip between misting intervals

Question 11

Mist system controllers

Answer 11

Static (set on a timer and time intervals.) Dynamic ( environmental triggers such a dryness (artificial leaves), light accumulations (quantum light sensors) and the VPD.

Question 12

Peat and Coir pellets

Answer 12

Peat is from bogs and it is organic and finite coir is from coconut and is an increasing organic material used for moisture retention it too is finite.

Question 13

Polyethylene Tents

Answer 13

Moisture retentive tents can be used to keep the humidity near 100% until cuttings are rooted. Aluminum pipe frames are constructed to hold the tents over the cuttings or sheets can be directly laid upon cuttings raised on a bench or places on flats on the floor.

Question 14

Quantum Light Sensors

Answer 14

The computer triggers a
misting event after a
certain number of
accumulated light units.

Question 15

Rooting cubes

Answer 15

Getting those cuttings to root just got easier. This higher density, lower drainage foam, primarily designed for propagation of vegetative cuttings, encourages fast root development and optimal callus growth. Its finer-celled design offers greater contact with the cutting’s cut end, for easier and more rapid water uptake.

. Its cell structure creates a perfect air-to-water balance for fast root development and optimal callus growth. And it’s ready to use: just wet it and get planting

Question 16

Solenoids

Answer 16

Solenoids receive an electrical signal from the controller to
open a valve and begin a misting interval

Question 17

Static vs Dynamic Mist Control

Answer 17

The static controller is a 
time clock that sets the 
mist interval and duration. 
There may also a 
day/night sensor that 
prevents misting at night.

Dynamic control uses the
environment or signals from
the plant to schedule mist

Question 18

Substrate Properties

Answer 18

Hold cuttings in place. Provide moisture to the cutting. Permit air exchange. Provide a dark environment. Organic- peat, coir, bark
Inorganic- Perlite, vermiculite, expanded shale, sand.

1. Adequate moisture
   Water holding capacity 20 - 60%
2. Well-drained with good aeration
   Air-filled porosity 20 - 30%
3. Pathogen-free
4. Low soluble salts
5. pH between 5.5 and 6.5

Question 19

Substrate temperature and rooting

Answer 19

Air temperature at 70 oF days / 60 oF nights.

Rooting medium at 70 - 75 oF.
10 oF higher for tropical plants

Question 20

Thermal curtains

Answer 20

Black shading curtains ontop of the greenhouse or propagated plants may be necessary to reduce heat from high light levels

Question 21

Transpiration

Answer 21

Water loss from the leaf
is mainly through the
stomata.

The driving force for 
water loss is the 
difference in vapor 
pressure between the leaf 
and air (VPD).

Question 22

Traveling Boom

Answer 22

An alternative to solid set stationary
mist systems are traveling.

These can be used to mist cuttings
or irrigate after rooting.

Question 23

VPD Vapor Pressure Defecit

Answer 23

Water loss from cuttings results from the
difference between the vapor pressure between the
leaf and the surrounding environment.

Under conditions where the stomata are open and the VPDair
is lower than the VPDleaf there will be a loss of water from
the leaf by transpiration

Ex: The inside of the leaf is 100 but the outside is 75 causing transpiration to occur.

Question 24

Vapor pressure models

Answer 24

Sensors (light, temperature, 
humidity) send data to a 
computer that calculates the 
vapor pressure deficit for 
the greenhouse environment. 
Crop models use VPD to 
estimate water loss from 
plants to initiate irrigation.

Question 25

Water quality and rooting

Answer 25

Low salts < 0.75 mS
Low alkalinity sodium absorption ratio < 5
pH between 5.5 and 7.0

It may be necessary to have a water purification system. And a particulate filter.