I haven’t had much luck growing plants on the Shrimphaus river.  Mostly they dry out either immediately or eventually, or sometimes they rot away.  This roots and bottom bits wet all the time but leaves out in the air niche is pretty challenging.  Some internet digging revealed plants that thrive in this setting are called marginal plants:  those growing on the margins of bodies of water, and they are popular for people with ponds.  Ok, so that’s the right setting, but outdoor ponds are much larger than the Shrimphaus so only the smallest marginal plants might work.  Some shopping around led me to try Bog Arum (Calla palustris), Golden Buttons (Cotula coronopifolia) and Golden Creeping Jenny (Lysimachia nummularia ‘Aurea’).  All of these are listed as growing to a maximum height of about 6 inches.

The plants arrived well-packed in wet newspaper and the first surprise was how big they all were.  The pond world operates on a much larger scale than the aquarium world!  

Marginal plants in and around the river

marginal plants in the river
newly planted

With the bog arum I cut the bottom piece off so it was flat, lay that on the slate surface of the river, spread out the roots and covered them with small rocks.  I had some concerns it would be unstable and fall over but seems ok so far.  The golden buttons was too big to go on the river, so after some thinking I planted it around the back in the aquasoil substrate with the leaves hanging out above the waterline.  The catch is the guidance on golden buttons suggests a planting depth of 0 – 10 cm (under the waterline) and in the Shrimphaus at the back the depth to waterline is 12 cm, so a little on the deep side.  The creeping jenny was pretty straightforward to plant in amongst the small river rocks. By time all the bits and pieces from the big mass of creeping jenny was pared down to viable material there wasn’t actually a huge amount left, but it’s enough for this go. Those following along at home may recall golden creeping jenny was originally tried fully submersed in the Fireplace Aquarium but didn’t really work out very well – hopefully this riparian/marginal setting will be better.

Marginal plants two week update

The bog arum got off to a great start, perking right up.  It had one leaf wilt away which I removed but also sent up a new leaf from the centre of the plant and that new leaf reached what looks to be full-size after a week of growth.  The golden creeping jenny I think is doing well.  Looking at the time-lapse photos it appears to have settled in and may have grown a little bit.  One of the creeping jenny stems because mouldy so I cut that off and the rest of the plant is doing ok.  The golden buttons seems not doing not so well.  The leaves rather than firming up have become droopy, and looking underwater the stems may be rotting away.  I suspect this plant might struggle when previously above water pieces are fully submerged – it might rather have to grow in submersed form until reaching the water surface and then transition.

Other marginal plant possibilities

emersed Pogostemon erectus
emersed Pogostemon erectus

I had an interesting ‘discussion’ with ChatGPT about marginal plants and it suggested, amongst others, Blue Star Creeper (Isotoma fluviatilis).  I tried ordering some online but what I wound up purchasing inadvertently was Isotoma axillaris seeds.  The packet warns “do not overwater” which does not sound promising, but I put about a dozen seeds in between the river rocks and we’ll see what happens.  I had maybe more luck with the the Royal Horticultural Society’s find a plant website which both suggested Iris cristata and provided a link to a mail-order supplier so I put in an order for two plants and we’ll see how that goes as well.  I also still have some hope for success with Pogostemon erectus which was on magnificent display with happily growing fully-emersed foliage at Aquarium Gardens – I picked some up and it’s been in the Shrimphaus for 6 weeks so far.  More on that as well in due course.

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