When the plant container is full of roots to such an extent that the plant will become starved of nutrients.
Used of a pot-grown plant whose roots have completely explored the growing medium and are now densely packed into the container, often becoming woody and constricted. Pot-bound roots may wind themselves round and round the inside of the pot, making an impenetrable wall. On re-potting, pot-bound roots are unlikely to spread out into the new soil or compost unless first being physically loosened by the gardener. It is best to avoid pot-bound conditions by timely potting-on and planting out. Affected plants are likely to be starved, dry, and less vigorous once re-planted.
Refers to the state of a container grown plant where the root growth has filled the container to the extent of eliminating all vital air spaces. When a plant gets too large for its pot, the roots circle around inside the pot and start to restrict themselves. If your plants seem to dry out more quickly than they used to, but are otherwise healthy, they are probably pot bound. There are simply too many roots in the pot and not enough soil is left to hold and distribute water.
The condition of a pot-grown plant when the root growth has filled the pot to the extent of eliminating all air spaces.