Marginal Plants: the plants that grow round the pond edge in the shallow areas. Choosing and planting water plants - Part 2

Marginal plants provide protective cover too especially for the entry and exodus of animals to and from the pool. Their usefulness in the pool environment is that they are great users of nutrients and also serve to ‘landscape’ the pool into garden scene. They are called ‘marginals’ because they are generally planted around the margins of the pool, although between them they are tolerant of a quite range of water depths. In general they thrive in depths of water between 5 and 15cm above the soil they are planted in. This tolerance distinguishes them from Bog plants in that these will only tolerate moist soil where the water is draining away from the plant and not in a static slop.

The Pond Edge is a Spring Garden

Caltha palustris: the clarion of spring.
The emergence of the marginal plants is a clarion of spring, ( Marsh Marigolds, Caltha palustris being the first to flower ). Marginal plants help to use up the nitratesThe stream in Pete Sims tranquil Summertime, Hampton Court 2007: Marginals softening the hardlandscaping and blending in with the damp lovers that just like to be near water and not in it. in the pond and some of them are very quick to absorb many of the toxins that might otherwise permanently pollute our waterways and wetlands, rushes and reeds in particular. They provide valuable cover for the continuous traffic of wildlife in and out of the pond. To the pond constructor they can help hide the weaknesses of the design such as the intrusive pipework or the little bit of visible liner. Visually, they soften a hard paved or rock edge to the pool.
For the picture of the garden as a whole, they can help blend the pool into its setting. Many marginal plants are happy to double as bog plants or even ordinary border perennials. Using some of them outside of the pool in a separate boggy backdrop can disguise the precise line of where the pond ends and dry garden begins.

Even though many marginals are spring flowering, their period of interest can be continued with the range of variegated and coloured leaved varieties. For instance, there is the variegated form of the Sweet Flag or Scented Rush, Acorus calamus variegata, or the miniature version for smaller ponds, Acorus gramineus variegata (gramineus means 'grass leaved'). There is a yellow clumping golden grass, Carex riparia 'Bowles Golden'. A variegated form of the yellow flag iris, Iris pseudacorus variegata Acorus calamus variegatusand the blue Iris laevigata variegata. There is a conversation piece in the 'Zebra Striped Rush', Scirpus lacustris ssp. tabernaemontanae ‘Zebrinus’ (often referred to just as Scirpus zebrinus) that has horizontal variegation. For a bright splash of lush variegated colour there is the Water Figwort, Scrophularia auriculata variegata.
The aristocrats of the marginal plants are the Irises, particularly the ensata hybrids, previously all under the banner of Iris kaempferi. They are the clematis flowered Iris with colours varying through white, blue, red, violet and crimson, often with bold and elaborate markings.
Those of you keen on the perennials of the herbaceous border may be surprised that Houttynia cordata, Lobelia cardinalis, Iris sibirica and even some Hostas appear on the retailers lists of marginal plants. The latter two may survive but they wont flourish in very marshy conditions. Rockery plant enthusiasts will spot the all-terrain Sisyrinchium californicum and S. burmudianum and the multipurpose Creeping Jenny, Lysimachia nummularia . Flower arrangers will spot the stately arum lily, Zantedeshia aetheopica. Herbalists will find Water Mint and chives. If we go back into the history of herbalism and medicinal the plants, these plants I am calling ‘marginals’, plants of the marsh and soggy wetlands must have offered up more cures for ailments and diseases than any group of plants from any other habitats.Iris ensata,varieties with lysamachia punctata variagata Not only that, many of those indigenous to this country, particularly the reeds and the rushes, were an essential raw material for man’s service and comfort. From thatching for roofs, to lights at night; materials for baskets, beds and pillows and even food, it is hardly surprising that many tribes of early man lived near or amongst these plants that did so much to sustain them.
Even today we still use these plants, particularly the Norfolk or common Reeds which is used to clean and extract pollutants from the water effluent from domestic and commercial premises. This is an important and sustainable method of dealing with raw sewage particularly for landlocked counties that have rivers and waterways to conserve.

NATURAL PLANTING OF THE POND EDGE PLANTS

If you were keen to establish a conservation style of water garden with indigenous plants, then choose your plants carefully. Dont turn your back on it for too long as all the plants will be overgrown and in amongst each other battling about - a bit like a classroom of year 9 schoolboys left to their own devices for five minutes! When choosing plants for a 'free-rein' natural planting, be wary of 'give-aways' and bargains. Try to see what a mature clump looks like (a 4-5year old plant). This will give you much more positive idea of its real characteristics.

PLANTING MARGINALS IN AQUATIC PLANTING BASKETS

Myosostis palustris, Water Forget-me-notVeronica beccabunga, Brooklime
Allow one marginal for every 5sqft of pool surface area. Instead of planting them in a line all round the edge of the pool. Try to get some depth to the planting by having some in front of others. If the shelf is only wide enough for one basket is there room to plant outside of the pool and behind with a backdrop? Otherwise use the groundcover characteristics of plants like Creeping Jenny (Lysimachia nummularia), Brooklime (Veronica beccabunga), Mimulus and even Water Forget-me-Not (Myosotis palustris). Plant one of these in with a taller growing plant in the same basket. However, having said that, some marginal plants do not make very good bedfellows so if you do this dont be surprised to find just one in residence after 12months.

The rules and techniques of planting are:

Choose plants with strong fresh growth, not in flower. Plant at the same level as they were in the container you have taken them from.
Line an aquatic basket with a hessian square. There is a make of aquatic basket that has very fine mesh to the side of the basket that does away with the need for a hessian liner. They are called ‘Finofil’ and are designed also to allow plants to outgrow their containers without too much hindrance.
Fill the baskets with chemical free fibrous loam or aquatic soil to roughly 50mm from the top of the basket.
Plant the plants or offsets in the loam and top up the soil level to almost the top of the basket but allowing enough room for a layer of pea gravel. If it is early in the season, the new growing tip should be just showing at the surface.

Place the plants in the water with the shoots roughly at water level.

Fill the aquatic planting basket with heavy loam.: If the soil is sandy or silty or the pond contains koi, line the basket with a hessian liner

Several plants of different habits can be used in the same basket. Plant them in opposite corners: Half fill the basket and place the plants in position.

Backfill between the plants with soil and firm into place.

The plants should sit roughly 3 or 4cm below the edge of the basket. Cover the surface of the soil with 2cm layers of peagravel.: this will prevent the soil washing away on the surface and inhibit the attentions of fish. As a general rule, place the baskets with the edges just below water level.

As a general rule, marginal plants are happy sitting up to their necks in water i.e. the water can just cover the top of the basket by little more than half an inch. If there are areas that are a little deeper (2-4ins /5 - 10cm) then Alisma plantago (Water Plantain), Calla palustris (Bog Arum), Menyanthes trifoliata (Bogbean), Orontium aquaticum (Golden Club), Pontederia cordata (Pickerel), Saggitaria saggitifolia (Arrowhead)and Typha latifolia (Reed Mace) will all happily exploit these conditions. Zantedeschia aethiopica (Arum Lily) will thrive in a depth of 15-23cm (6" - 9").

To see more of the plants available to the water gardener as marginal plants and to find out the season of interest, height and habits see our constantly updated Plant Directory of Readily Available Plants.