Marginal Aquatic Plants, are those that grow in the shallow waters around the edge of the pond. Some marginals will also thrive as bog plants. However, there is a difference.
Marginal plants normally grow in water with a depth of 6 - 12in (51 - 30cm) and are normally quite attractive with either flowers, foliage, or both.
They are an important group of plants in the pond, for they provide shelter for small fish, either by way of stem and root clusters, or simply shelter from strong sunlight by means of their foliage.
Most marginal pond plants are herbaceous perennials - they die down in the winter to re-emerge the following spring. As such, they can be divided in spring to either confine their growth, or to provide extra plants.
One of the problems with the taller-growing marginal plants, is that of support. They are best planted in containers with soil, and placed in a sheltered area of the pond. A brick or slice of stone placed on top of the container will give it some weight to hold it down. The stone will soon 'mellow' in appearance with algae-like covering after a few weeks.
Caltha Palustris - the Marsh Marigold, is one of the first plants to flower in and around the garden pond.