Despite the fact that the main pond is still not paved or ready for planting, the small pond, which has been home to the waterlilies, is getting crowded and I have been repotting some and transferring them. Gardening in ponds still seems an odd occupation to me. It all seems so alien and somehow uncontrollable. Firstly there is this other world that seems so mysterious. You have to make sure the waterlilies are well fed or they won’t grow well but then you have to keep the water low in nutrients or algae goes crazy and turns the pond into thick, green soup. We have to plant to cover the water surface to shade the water to prevent algal growth but then what is the point of having a pond? We have to reach an equilibrium between plants and water – and wildlife or fish – and that takes time.
To complicate it all, waterlilies need different depths of water over them and the plants around the edge also need to be planted at different depths, though most are not too picky.
What always seems particularly galling is the cost of water plants, most of which are native, and which, after a few years, are unbelievably invasive and need to be cleared out by the barrowful.
And then there is the magic soil. Bags of aquatic soil cost a fortune. Soil for planting needs to be heavy, clay and low in organic matter. That sounds exactly like my native soil. But I am scared to use it in the planting baskets. So I am wasting money (possibly) on bags of aquatic compost in planting baskets.
The waterlilies have been in their initial baskets for 30 months, having been bought as bare root cuttings in August. At this stage they need moving into larger baskets and they will go into the large pond. They have been fairly happy, in pots almost touching, in the small pond for two years. Lilies have different growth habits and some are neat and form clumps. They are going to be easy to repot. But others produce long rhizomes and these are more of a problem to tackle. This is partly because these rhizomes get tangled with surrounding plants and the long, white roots from these root into the debris at the bottom of the pond. It is a messy and smelly job. I should state that there are no frogs in the pond at present. There are fish, that came in as eggs with the plants. Six reached maturity and they disappeared for a few weeks recently and I thought a heron had had them, but I think they were just canoodling in the pond weed.
So I lined the mesh baskets with weed fabric. I would have preferred to have used hessian but this is what I had available. I confess that I put some ‘native soil’ in the base. In ‘wild’ ponds you can plant lilies in the clay lining so my compromise will be acceptable I think. I will emphasise that this ‘soil’ has very little organic matter. Then I added aquatic soil. I reached into the pond and lifted out a lily. Most of the plant was straggling beyond the basket and I snapped it off and tidied it up. I chopped through the soil ‘lump’ and potted the back of the old rhizome in the new pot and then the long rhizome, which was trimmed to about 20cm, and planted it with the cut against the side and the growing tip in the centre of the pot. I placed more compost over the roots and then covered the whole pot with gravel.
The basket then had to be placed in the pond gradually so the compost did not all lift. At present these are in the big pond, about 15cm below the surface to settle. I have ordered some lily food which will be pushed into the compost when they start to settle. I am hoping that these pots will keep the lilies happy for a couple of years. Two done, nine more to go, if they are all alive. That’s the problem with ponds – you can’t just check as you wander past.
I am also adding a few marginals in shallow baskets. These are important to allow access and cover for creatures entering and leaving the pond as well as being attractive.
I mentioned about having to get rid of great quantities of aquatic plants after a few years. When removing any pond plants, always leave them beside the pond to dry out for a day so any creatures can pop back into the pond. And then add them to the compost heap. Never dump them into wild ponds in case they are not native and can upset the natural balance.
I repotted some irises a few years ago and used garden soil and have spoiled our pond as it now has a covering of duckweed and huge amount of algae. I haven’t gone back to repotting them in aquatic soil as of yet though. Maybe next year!
I would have thought that as the iris grew it would soak up the nutrients. And I am sure your soil is a lot better than mine and full of organic matter – which may have been the problem. This gardening lark can be very complicated. I have planted hippuris – a native – and was reading up on it and it appears that it releases methane into the atmosphere – sucking it from the decaying matter in the bottom of the pond and releasing it into the air! So much for my pond being good for wildlife and the environment!
Ah, sure, we’ll do our best!
Great article, thank you. I often wonder what to do about my waterlilies. Their root clump is now so large and heavy it’s impossible to get it out of my pond. Enjoy the wonderful flowers in summer but I wonder about the root clump now out of control 🤷
I think that if it has rooted into the debris in the bottom of the pond it is probably best to leave it to get on with it while it is still healthy. Only when it starts to suffer or get too close to the surface need it be tackled.