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Three growth forms described for Salvinia molesta also pertain to S. minima. During favorable growing conditions and in the absence of competition for space, the leaves of S. molesta and S. minima will float flat on the water surface. During this ‘primary’ growth form, leaves are small (up to 1.5 cm wide) and internodes are long. A ‘secondary’ growth form is exhibited by plants found especially along the edges of developing mats where the leaves broaden and become keeled in the open water. The ‘secondary’ form is recognized when the entire underside of the floating leaves remain in contact with the water surface. The ‘tertiary’ growth form occurs when plants become tightly compressed into a ‘mat’. Floating leaves are broad and large (up to 6 cm wide) and internodes are relatively short. The most notable difference is that the floating leaves fold along the midrib and most of the undersides of the leaves are no longer in contact with the water surface.
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