Solving pond plant problems with newly established ponds

Depending when and where you have created your water garden it may seem that many plants take a long time to get established. If you have been able to fulfil all the correct criteria in regard to sitting, establishment and stocking levels (see: Avoiding Problems from the Start, Establishing Your Pond, Stocking Levels) it may be simply be due to the weather.

Water plants, in common with all other plants, need prescribed levels of light, water, nutrition and temperature in order to thrive.

1) In the UK, Marginals and lilies need as much sunlight as possible in order to flower and oxygenators need it to photosynthesise and produce oxygen. Any sort of shade upsets this to a very large degree. Hot sunny countries can be partially shaded, especially in the midday sun. However the pond can be too exposed especially to cold winds from the north and east.

This pond took ages to get established, hindered by cold winds from the east. The fact that grass carp were introduced at a very early stage did not help either. Eventually the carp had to go.

2) A prescribed depth of water in which to grow is naturally essential for happy marginal plants and lilies, although some marginals are extremely adaptable to dry conditions and some lilies are encouraged to flower extremely profusely in half their normal planting depth. It is change, particularly persistent change in water level, which will not be tolerated. So beware if you waterfall or stream, when it is turned off or on, radically upsets the water level.

Too much turmoil especially for lilies is also an upset. Ensure that your submersible pump turns over less than the total volume of the pool every hour. Turning over the total volume every two hours is the level to aim for.

Lilies cannot tolerate the constant spray from fountains. This newly planted specimen in a show garden will soon succumb to foliage problems. A lilys leaves are its snorkel to the outside world.

3) Change in temperature also upsets water plants. Although the biological clock in most marginal plants makes them 'early risers' in the spring and they seem to plod on in the most miserable conditions, a sudden change in temperature from mild southerlies too a cool north wind can soon blacken them off. Just minor changes in temperature can produce a check in growth, which is when the grey mould of mildew can arise opportunistically on Marsh marigolds and Forget-me-nots.

Marsh marigolds, the tips of Irises and bog Arums easily fall prey to frosts. Although well-established plants recover when they 'come again', freshly established plants standing alone and vulnerable without the resources and protection afforded by a group planting, easily fall prey to extremes of weather or temperature. Combine this with the fact that many marginal plants that are sold for retail in garden centres are 'brought on' in greenhouses and poly-tunnels to take advantage of the early season sales, it is then no surprise that newly planted water gardens just get mown flat by the late spring frosts. The lesson learnt here would be to buy when conditions are suitable for the plant to be outside, or to harden off newly purchased plants when you get them home by giving them frost protection during the night for the first three or four days.

4) Any fertiliser that is available to a newly planted water plant will only be used if the above conditions are right. Slow-release fertiliser in the planting basket just becomes a pollutant.

When newly planting or replanting a pond only use fertilizer specifically for aquatic plants and only use it in beginning or at the height of the growing season.

On the other hand, even if the above conditions are right, growth cannot be expected unless there is some nutrition available. There should not be a lot in the fresh water, and naturally occurring nitrates will only be available to plants once there is a fully established cycle of life in the pond. The bucket of water from an established healthy pond trick, 'Pond Starter' chemicals and the introduction of fish, all help to get things going.

5) Big, bored fish, especially carp - if they are introduced into the pool too early, can be a menace grubbing around in lily baskets until the tubers float to the surface.