Apical dominance is the tendency of the main shoot tip to grow fastest while holding back the buds and branches below it. Auxin made in the apex moves down the stem and, together with cytokinin and strigolactone signalling, keeps axillary buds dormant or slow. The result is a single-leader, "Christmas tree" shape.
In practice
Almost every training method is a way of breaking or redirecting apical dominance:
- Topping and FIM remove the apex, releasing the buds below.
- LST bends the leader down so that side branches sit as high and receive as much auxin relief and light as the top.
- Mainlining and manifolding combine topping with symmetrical shaping.
- SCROG spreads every tip level under a net.
Cultivars differ a lot. Some have strong apical dominance and grow one fat main cola; others branch freely on their own. Autoflowers, which can't spare recovery time, are better shaped by LST than by topping (house position).
Don't confuse with
- Apical meristem: the tissue; apical dominance is its effect.
- Phototropism: bending toward light, a separate auxin response.
- Stretch: elongation in early flower, not branch suppression.
The zone of dividing cells at the very tip of a shoot (or root) that produces new leaves, nodes and stem; removing it is what topping does.A class of plant hormones, chiefly indole-3-acetic acid (IAA), that drives cell elongation, apical dominance, bending toward light and root formation.A dormant shoot bud in the angle (axil) between a leaf and the stem at each node, able to grow into a branch or a flower cluster.LST (low-stress training) bends and ties stems so the plant grows wide and flat, exposing more bud sites to light without cutting or breaking tissue.SCROG (screen of green) trains a few plants under a horizontal net, tucking shoots so the canopy forms a flat, evenly lit layer of many tops.The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.A day-neutral cannabis plant that starts flowering by age, usually a few weeks after germination, regardless of light schedule; the trait is mainly recessive.The stretch is the rapid increase in height in the first two to three weeks after switching to flower, when many cultivars grow 1.5 to 3 times taller.A class of plant hormones made mainly in roots that promote cell division, shoot and side-bud growth, and delay leaf ageing.
