We all agree that controlling nutrients is really, really important. But nutrients in water tend to be a lot more mobile and available than in soil, so maintaining low nutrient levels in a pond can be difficult for many gardeners. Growing smaller and less invasive plants is an insurance policy against nutrients finding their way into the pond.

All of this doesn’t mean it’s impossible to grow large marginals in a small pond without any problems. It’s just harder to do. That’s why I think the advice to grow smaller plants is good advice. Also, many of the smaller species are, frankly, more ornamental and more threatened in the wider countryside.

Digging out ponds can be beneficial but it can also cause damage to communities of plants and animals which live in weedy or vegetated ponds. I would recommend the Pond Book as the main text to refer to when looking at these sort of issues!

Regards

However Jeremy does give the advice that in a small pond you can hoik a bit out when it is taking over. The management of a pond should be a good clear out of the vegetation in the winter to mimic say grazing animals – removal of vegetation and the creation of bare areas is all about creating a good pond habitat.

Its just goes against the ‘pond advice myths’ which are often given out. I have common reed in my pond which is approx 1m in diameter and around 20cm deep. I have to say that the spread of this plant has been very slow possibly due to the low nutrients in the water – so effectively these invasive plants become so when conditions allow them to be.

Reedmace is a good wildlife plant in the wild, but it’s just too large for most ponds – just like common reed, weeping willow etc. Even in the wild it quickly crowds out most other plants and will shade out that warm shallow water you have so carefully created. Even in bigger ponds and ornamental lakes it will need regular cutting. Like most pond plants, introducing it is easier than controlling or removing it. You have been warned!

There are masses of good emergent plants you can grow that are much less thuggish – my favourite is Eleocharis palustris (spike-rush) which only grows to about 20cm and forms an open mat through which other emergents and submerged plants can grow. Or how about flowering rush Butomus umbellatus, or lesser marshwort Apium inundatum? Several of the sedges are also good – I grow bottle sedge Carex rostrata, which seems to go down well with the toad population. But even this needs annual control.

Dragonflies are not generally fussy about what species they oviposit in and you certainly don’t need Typha to have breeding southern hawkers. I’ve had them ovipositing in soft mud by the side of my parents pond, and I think they will use a variety of plants such as flag irises and bog bean.

Debbie – difficult to explain your oily surface without seeing the pond. But I have seen this around Typha and other tall emergents before and it’s generally quite common in sheltered ponds. I think it’s a bacterial film on the surface of the water, probably caused by an accumulation of organic matter in the pond combined with a lack of wave action. The bulrushes may contrbute to this by adding leafy material and by reducing turbulence and hence oxygen concentration. The bacteria themselves are generally harmless but you may see a reduction in the amount of oxygen dependent species such as mayfly nymphs.