Root-bound (or pot-bound) describes a plant whose roots have filled the container and begun circling the walls and base, leaving little medium to hold water and air. The plant may wilt within hours of watering, need water far more often, show slowed growth, and stall after a flip because it cannot support the stretch.
In practice
Signs: roots poking from drainage holes, a root ball that lifts out as a solid white or brown mat, runoff appearing almost instantly. Fixes are to up-pot, or in flower to increase watering frequency rather than disturb roots. Fabric and air-pruning pots reduce circling because root tips that reach air stop elongating and branch instead.
Being "full" is not automatically bad. A pot that is fully rooted at harvest is using its volume efficiently, and with frequent fertigation a small, full pot can still produce a large plant.
Don't confuse with
- Overwatering: drooping from saturated, airless medium; a root-bound plant droops from running out of water.
- Root rot: brown, slimy, smelly roots from pathogens such as Pythium; a different problem.
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.Runoff is the water or nutrient solution that drains out of the bottom of a container after irrigation; growers test it to see what is happening in the root zone.An air pot is a rigid container with cone-shaped holes in its walls that air-prune roots, preventing circling and drying the medium faster than a solid pot.Fertigation is delivering fertiliser dissolved in irrigation water, so plants are fed every time they are watered rather than through solid amendments.Overwatering is watering so often that the medium stays saturated, starving roots of oxygen, which causes drooping, slow growth and root disease.Decay of roots by pathogens such as Pythium, Fusarium, Rhizoctonia or Phytophthora, usually triggered by low oxygen, heat and waterlogging around the roots.A genus of oomycete water moulds, such as Pythium myriotylum and P. aphanidermatum, that cause brown, slimy root rot, especially in warm hydroponic systems.Up-potting moves a plant into progressively larger containers as its roots fill each one, instead of starting in the final pot.Pot size is the volume of medium a plant roots into; bigger pots give bigger plants within reason, but feeding frequency can let small pots punch well above their size.A fabric pot is a breathable, sewn felt or non-woven container that lets air and water through its walls, drying the medium faster and air-pruning roots.Transplanting moves a plant and its root ball into a new container or the ground; done gently it causes little shock, but GenetixBay advises against it for autoflowers.
