1. A plant that is aged, mature, or has been growing for a long time
The old plant in the corner of the living room has been there for over twenty years.
A planta velha no canto da sala de estar está lá há mais de vinte anos.
2. In botanical contexts, a plant in its mature or senescent stage of growth
The old plant shows signs of decline despite regular watering.
A planta velha apresenta sinais de declínio apesar da rega regular.
3. Colloquially, something outdated or obsolete (figurative use)
That computer is an old plant; we need to upgrade.
Esse computador é uma planta velha; precisamos fazer uma atualização.