Aquatic plants like Phragmites australis and Typha domingensis grow differently depending on water depth and whether they are alone or with other plants. Phragmites australis prefers shallow to medium water depths, while Typha domingensis likes deeper water. When they grow together, Phragmites australis still likes shallow to medium water, but Typha domingensis prefers medium to deep water. As the water gets deeper, both plants grow taller and denser. When they grow together, the number of leaves and stem size is lower, but plant height is higher. The plants interact with each other and with water depth, affecting their growth.