Plant Propagation and Nursery Production
Propagation is either sexual (seed) or asexual (vegetative). Candidates must understand seed biology: dormancy types (physical, physiological, morphophysiological), scarification (mechanical, chemical, hot water), stratification (cold moist), and the conditions for germination (moisture, temperature, oxygen, sometimes light). Know seed quality factors: viability, vigour, purity and germination percentage.
Vegetative methods include cuttings (softwood, semi-hardwood, hardwood, leaf, root), division, layering, grafting and budding, and tissue culture. Understand why cuttings root: auxin, wounding, node position, juvenility, and environmental control (humidity, mist, bottom heat, light). Know the difference between a node and an internode, and why cuttings are taken just below a node. Grafting requires cambium contact and compatibility; budding uses a single bud.
Nursery production covers media, containers, irrigation, hardening off, hygiene, and plant quality standards. Hygiene is critical: sterilise tools, use clean media, and isolate diseased stock to prevent spread.
Traps: taking cuttings from flowering or diseased stock; forgetting that some seeds need light to germinate while others need darkness; and assuming all cuttings root at the same time of year. Another trap is confusing stratification (cold) with scarification (breaking the seed coat).
Worked rule of thumb: for a difficult seed, ask 'what is the barrier?' - a hard coat needs scarification, an immature embryo needs stratification, and a light requirement means surface sowing. Match the treatment to the barrier.