1. Essential environmental conditions for rooting leafy cuttings
maintenance of leaf turgor
ample light (but without heat build-up)
a good rooting medium (clean, moist, well-aerated, well-drained)
optimal air and medium temps (65°-75° F or 18°-24° C)
control of disease-causing organisms
harvest cuttings from disease-free stock
frequent disinfection of harvesting tools
if necessary, fungicidal and/or bactericidal dips

2. Environmental control systems for rooting leafy cuttings
poly tunnels, cold or hot frames, lath houses (historically)
large-scale outdoor shade and/or misted areas
greenhouse systems
poly film or contact sheet (non-misted)
intermittent misted areas (enclosed or open)

3. Intermittent mist: features
suspended misting nozzles with an on/off cycle (e.g., 6 sec on, 2 min off)
works by reducing both leaf and surrounding air temp (via evaporative cooling) and raising RH
optional bottom heat controls medium temp drop

4. open mist: outdoor and greenhouse propagation
Types of mist systems
open mist: outdoor and greenhouse propagation
enclosed mist: poly tents in greenhouses
increases RH control (around the cutting)
useful with difficult-to-root species, softwoods with large leaves, and broadleaved evergreens

5. oil burner (aka pressure jet or whirl nozzle)
Mist nozzles: types
oil burner (aka pressure jet or whirl nozzle)
water forced through grooved orifice under pressure
more expensive, uses less water
deflection or anvil nozzle
pressurized water passes through an orifice, striking a flat surface
cheaper, uses more water

6. Mist controls (that turn on the system and time the mist cycle)
electric timers (2 electric clocks)
electronic timers (use a photoelectric cell to turn the system on)
screen balance (small steel screen that mimics a leaf)
photoelectric cell/condenser (measures light energy “accumulation” to lengthen or shorten the interval between mistings)
computer controls (have been used to control travelling mist booms, for instance)

7. Solenoid wiring (important because cuttings can be lost in 10 min
Solenoid wiring (important because cuttings can be lost in 10 min. of dessication)
for outdoor systems, use a “normally open” solenoid (the valve is normally open when electric power becomes disconnected)
for greenhouses, a “normally closed” solenoid (electric current is necessary to open the valve) can be used, if:
power failures are infrequent
there is a manual bypass valve

8. Types of fogging systems
centripetal foggers: water ejected from a spinning nozzle, avg. 30 µm droplets (40 µm is min. for suspension)
high pressure foggers: water under psi produces 20 µm droplets on average
pneumatic or ultrasonic nozzles
compressed air and water disrupted by sound waves
high energy requirement, not practical for large propagation ranges

9. Fog systems: advantages over mist
maximum air cooling
minimum leaching of nutrients from leaves
maximum aeration of medium
minimum medium cooling

10. Features of fog systems
greenhouse shading is important to prevent solar heat build-up
good fan ventilation is needed
heat removal from the leaf depends on it, because the leaf surface isn’t wetted directly
controllers attempt to maintain a fixed RH

11. Hard-to-root species aided by fog*
Acer platanoides ‘Crimson King’
Betula pendula ‘Purpurea’
Castanea sativa (Spanish chestnut)
Tilia cordata ‘Clone 23’ (Linden)
Viburnum carlesii ‘Aurora’
Malus x domestica ‘M9’ and ‘M111’
*Harrison-Murray (1988) Acta Hortic 227:205