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

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)

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

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

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

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)

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

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 500-1000 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

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

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

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