An internode is the segment of stem between two nodes. Internode length is set by genetics and strongly modified by light, temperature and hormones (mainly gibberellins and auxin). It is the main component of plant height.
In practice
Growers talk about "tight internodal spacing" as a desirable trait: more nodes, more bud sites, denser colas. Typical indoor spacing in veg runs from about 2-5 cm (1-2 in) on compact plants to 10 cm (4 in) or more on stretchy ones.
What lengthens internodes:
- low light intensity or a lamp too far away;
- a high far-red to red ratio (shade-avoidance signal read by phytochrome);
- warmer days than nights (positive DIF);
- the first two to three weeks of flower, when most cultivars "stretch" 50-200%.
What shortens them: higher PPFD, more blue light, cooler days relative to nights, and training. A tall, gappy plant under a dim light is a light problem before it is a genetic one.
Don't confuse with
- Node: the attachment point; the internode is the space between.
- Stretch: the flowering-phase surge in internode length.
- Petiole length: leaf stalk length, separate from stem spacing.
A family of plant hormones (gibberellins, GA) that promote stem elongation, seed germination and, in cannabis, can shift sex expression toward male flowers.The dense, elongated cluster of flowers that forms at the end of a stem or branch; the main cola tops the leader.A family of plant photoreceptors that sense red and far-red light, measuring night length for flowering and shade for stem elongation.DIF is day temperature minus night temperature; a larger positive DIF lengthens stems, while zero or negative DIF tends to keep plants shorter.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.Photosynthetic photon flux density: the number of PAR photons landing on one square metre each second, in µmol/m²/s; the standard measure of light intensity at the canopy.Blue light is the 400–500 nm band; it keeps plants compact with shorter internodes and thicker leaves, but a high blue fraction slightly lowers cannabis yield.The stalk that attaches a leaf to the stem at a node; in cannabis it carries all the leaflets of a palmate leaf.The point on a stem where a leaf (petiole) and its axillary bud attach; branches, flowers and clone roots all originate at nodes.
