Trella uses a three stage growing model for its urban forestry seedlings. Their first season they grow in containers in the greenhouse. The next step is growing in the ground of our fields. The seedlings spend two years there. This allows them to establish extensive root systems and strong straight stems. But they can only stay in those fields for a short time because they are too close together there to grow any larger. This winter the trees will be dug up and replanted on wider spacing. They will grow for a further 5 years until they have branches and thick stout trunks.