Carefully pull down the branches of your cannabis plant, or the whole plant, tye them down.
You are now forcing them to grow horizontally. Tthe nodes will start producing branches or buds that grow straight up. Bending should be done gradually to avoid pinching or snapping the stem. Use soft hemp string or cloth to secure the branch or stem loosely when tying down to minimize damage to the soft stems. Growth is slowed for awhile as the cannabis plant adjusts to the shock of being bent. This is a good technique to maximize space in a small grow room.