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Build a Floating Bog

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Build a Floating Bog

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What You Can Do

We’ve been experimenting with a new technique for bog creation at our pilot project. Bogs are a threatened habitat in the UK, with many having been degraded by drainage and peat extraction. 

Why a Floating Platform?

Bogs require a very consistent water level to become established, so the easiest way to get one going is on a floating platform. We’ve found that sphagnum didn’t survive the early stages, but this is likely due to occasional drowning (see step 13). Many other plants have thrived, including rarities like Bog Asphodel. We’ll test again with sphagnum soon, now that we’ve identified the flaws with this method.

The Benefits of a Floating Bog

From a distance, this habitat is renowned as looking a bit boring – ‘MAMBA’ – miles and miles of bugger-all. But up close, there’s a magic tapestry of wetland plants and invertebrates, with sparkling dragonflies, sticky insectivores and fluffy-headed Cotton Grass.

The presence of aquatic plants in the bog has allowed them to become established in the pond below, despite highly-variable water levels and slippy sides, which would have made planting difficult. The floating platform also creates a more accessible way of interacting with pond life – invertebrates and plants are much easier to see on its surface.

Step by Step Guide

Step 01: Supplies & Tools

Supplies

  • 2x 2.5m Guttering Downpipe
  • 4x 90° Downpipe Bend (same diameter as downpipe)
  • Roll of 1m Galvanised Steel Mesh (4m long)
  • Roll of Galvanised Steel Wire (may come with mesh)
  • Roll of Thick Rubber Gardening Ties or Zip Ties
  • 70 – 100cm wide roll of Cotton Carpet or Coir (at least 1.5m long)
  • Fireproof Insulation Foam Spray Can
  • PVC Pipe Adhesive
  • Large Bag of Hay / Heather Clippings
  • Sphagnum grown sustainably
  • Aquatic Plant Seeds (gathered locally from bogs)
 

Tools

  • Saw
  • Wire Cutters
  • Gloves
  • Eye Protection
  • Scissors
 
Constructing a Floating Bog
You may also need a car that is long enough to contain 2 x 2.5m pipes. Alternatively, you can cut the pipes to 1.7m + 80cm at the DIY store.

Step 02: Take Supplies to Site

The easiest method for constructing this floating bog, and the least messy, is doing it on site. The resulting structure is likely to be quite light, but the glue and insulation foam will take time to set, so it will need to be left on dry land for a day or so after creation.

Constructing a Floating Bog
Don't forget to bring your tools and protective equipment! The best time of year to get a bog established is autumn (not summer).

Step 03: Cut Pipes

Cut the pipes to size with your saw – you will need two long sides of equal length and two short sides of equal length. These can be altered to suit your supplies, but in this case, I’ve suggested 80cm ends and 1.7m sides, which will make it easier to secure the wire mesh.

Constructing a Floating Bog
If you're using a hacksaw, you may need to flip the pipe over and tackle it from two sides, due to the solid top to the blade.

Step 04: Fit Pipes

Roughly assemble your structure, sliding on the 90° Downpipe Bends to check that everything fits together properly. Then remove one side at a time ready for the next step – glueing.

Constructing a Floating Bog
You can use end caps of the same colour - they weren't available when I was at the shop!

Step 05: Glue Pipes

Paste a generous ring of glue around each side of each joint, then reattach the 90° bend. Ensure that the bends are aligned flat to the floor plane (so that the structure is flat, not bent), as they are hard to move once the glue sets.

Constructing a Floating Bog
This glue will stick to polyester clothing and never come off, so be warned!

Step 06: Cut Wire Mesh Base

This is easiest to do with the base facing upwards (it’s reversible). Put on gloves and eye protection, as the cut wire is very sharp and may flick out. Overlap the mesh at the ends and the sides as much as you can, and secure one end first with wire ties through both sides of the mesh. Then pull the wire tight to the other end and clip off any excess wire with your wire cutters.

Constructing a Floating Bog
A roll of wire likes to stay rolled-up, so it will snap back into position when cut, and could blind you without eye protection.

Step 07: Secure Wire Base

Use wire to tie together the sides and ends of the bog very securely. The more ties you can use, the longer the structure will last and the less likely it is to fall apart when water levels change. So far, ours has lasted through two winter seasons.

Constructing a Floating Bog
These wire ties are the strongest part of the structure, and play a key role in its structural integrity.

Step 08: Drop in the Carpet

The cotton or coir roll is designed to act like a sponge – soaking up water and supplying it to the plants above. It also acts as an insurance mechanism, protecting the high side of the bog if it is lodged on the edge of the pond as the water dries out in summer. Cotton carpet is ideal for this – cut it to size in this step.

Constructing a Floating Bog
The original concept which inspired our bog (MoorLIFE 2020) used coir, but we have found cotton to be as effective. It does degrade more rapidly, but the root system will take over this matting role.

Step 09: Add the Hay/Heather

The hay or heather slowly decomposes, protecting the early stages before becoming the growing medium for the bog. This means that acidic plants like heather are likely to be better for this purpose. However, we used spare hay from old bales on site and this has been effective for many bog plants.

Constructing a Floating Bog
We originally presumed that hay decomposition may have helped contribute to clearing the water. But this is not barley straw, so it is likely that the compounds are incorrect for this effect.

Step 10: Plant the Bog

We think that the most effective way of getting a diverse bog established is with very small samples of sphagnum from existing mature bogs in your area (with the permission of the landowner). 

However, given the difficulty of getting landowner permission, and the issues with degrading bogs at scale, a legal alternative is gathering seeds of bog plants (or buying them online), and planting them in sustainably-grown sphagnum. Many bog species can also be bought as plug plants from Celtic Wildflowers.

You can place the seeded sphagnum or plug plants deep into the hay/heather, making sure that only the very top surface is exposed.

Constructing a Floating Bog
We used small samples of sphagnum from existing bogs, which had the benefit of a locally-sourced seedbank. But this is not sustainable on a large scale.

Step 11: Insulate and Cover with Mesh

Through trial and error (i.e. a sunk bog), we discovered that the tubes need to be filled with foam, or they will slowly fill up with water (despite the PVC glue). 

So, we drilled three small holes in the top of each tube and blasted fireproof insulation foam into each one until it started appearing out of the next one down the line. This type of foam does not have a water toxicity warning and we have had a huge abundance of invertebrate life in the pond since the bog was installed. After the foam has dried, you will probably want to chop off the messy little mounds that appear through the holes.

The final step is cutting and securing a mesh lid over the top with the rubber ties (pictured) – this is to the hay from blowing off, prevent birds from using the hay as nesting material or arriving and disturbing the bog while it is in a fragile state. We have also found that it prevents dogs from destroying the bog. The rubber ties allow you to easily remove the lid and add more plants at a later date.

Constructing a Floating Bog
The wire mesh prevents birds from pulling moss and other plant material out of the surface.

Step 12: Keep the Bog Afloat

After the foam has dried out, you can safely float the bog onto your pond. During spring and summer months, you will occasionally need to nudge it off the side of the pond as the water level drops. 

It also needs to be kept moving year round, to prevent the plant roots from attaching to the pond bed. This happened about 12 months into our project, causing the bog to ‘drown’ for a few weeks before I could pull it back to the surface. Drowning will kill sphagnum moss and some more delicate species – especially in nutrient-rich water.

Constructing a Floating Bog
Our first attempt slowly sank - we later filled up the tubes with insulation foam, and this has been successful ever since. These instructions reflect that hard lesson!

Step 13: Enjoy!

Inspecting your bog regularly will become a source of interest, as this habitat will change rapidly over the year. Succession happens quickly and a bog flora will soon become established. The shade created by the platform is a great hiding spot for aquatic life, so the pond next to your bog will likely be the most biodiverse spot. 

Our bog pond is by far the most rich and abundant of all our 7 ponds, with the clearest water. The bog was likely a contributing factor, alongside the introduction of bulrush seeds. The bog’s positive effects on water quality include the trailing roots reducing wave action on the shoreline; the plants spreading onto, and stabilising the sediment below; and the bog absorbing excess nutrients in the water. Newts appeared first in this pond, in the shelter of the bog’s root system.

Ecosystem restoration with a floating bog
One year after planting out.
Floating bog detail
Detail of bulrush, potamogeton and cotton grass.

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