PLANTS THAT LIVE ON THE EDGE

AWHILE ago we dug a pond in the garden. Even though it was all done by spade and wheelbarrow, digging it out involved taking out all the plants but the trees and completely clearing the site. In winter, this turned a lush, highly planted part of the garden into a building site.

But now we have finished the pond itself, replanted everything that had been temporarily removed and are starting to get the special character and feeling back into that part of the garden. But making a pond, especially if it is a naturalistic, informal one, is only the beginning of the process.

We could have left the pond simply as a circle of water filled only with reflections. But by using the ability of some plants to thrive while standing in shallow water we can create a link with the surrounding plants and thus integrate water and earth.

Marginal plants have evolved to have their roots in wet mud that’s often covered by water but most will survive for months out of the water as long as they don’t dry out completely. This means that they are ideal to make the link from the water’s edge to the soil on the margins.

By definition any pond creates a perfectly level, horizontal surface, so the first thing that marginal plants can do is add height and vertical structure.

I have planted the flowering rush (Butomus umbellatus), the water plantain (Alisma plantago-aquatica), the lovely porcupine-like striped bullrush (Scirpus zebrinus) and arrowhead (Sagittaria sagittifolia), as well as Iris ensata and the native flag Iris pseudacorus.

I also added the giant marsh marigold (Caltha palustris), water mint (Mentha aquatica), and the water forget-me-not (Myosotis scorpioides), all of which will spread into clumps without becoming unduly invasive and are very good for hiding the edge of the pond if, like mine, it is lined with butyl and edged with stone.

If you have a mud-lined pond, the marginals can stretch from dry land to permanent water without having to cross that artificial divide.

I use hostas, ligularias, primulas, rheums, gunnera, rodgersias and lysimachia planted in the borders around the water’s edge to keep this sense of unbroken flow of plants from the open water to dry land. However, because of the liner, all my marginal plants are potted up into special open-weave aquatic pots so the water can get in but the soil cannot get out.

All these plants have evolved to grow happily in very low levels of fertility so you buy them potted up in a loam-based, aquatic compost. You will also need some washed grit and aquatic mesh pond pots.

Put a good layer of grit in the bottom of the pond pot and then remove the plant from its original container and place it onto the grit before filling in the free space around it with more grit. You do not need to add any extra compost as the soil around its roots will be quite sufficient for the plant to grow healthily.

Cover the surface of the pot with a final layer of grit and lower it into the water so that it sits on the bottom. Most marginal plants like to have their roots submerged but their stems and crown above the water’s surface but are adaptable and can cope with being almost wholly submerged or in seemingly normal border soil as long as it remains damp.