bog garden alterations

Maidenhair fern after rain

Perth’s winter rains started in earnest this month and so far in May we’ve had 143.6mm, significantly more than the May average of 87.6mm. This is a good change after an extremely dry summer.

the bog garden was too effective

With all the rain since I planted out the bog garden, it’s been a bit too effective and last week pools of water formed on the surface that couldn’t drain away. I needed to rectify this design fault because standing water is an invitation for mosquitoes to breed. [1]

new shoots on Lepidosperma effusum

When I first dug out the pond in my garden I hoped water movement from the pond filter would be enough to deter mosquitoes breeding, but I needed biological control from Western Pygmy Perch (Nannoperca vittata) and White Cloud Mountain minnows* (Tanichthys albonubes). Both species coexist in the pond and have lived happily with tadpoles. The fish breed in summer and numbers fluctuate over the years, but there’s always enough to eradicate mosquito wrigglers (larvae) from the pond. Occasionally I’ve found wrigglers in stagnant water in bowls under pot plants, I tip the water in the pond and the fish have a feast.

after trimming the plastic the surface water could drain away

The fish can’t help with wriggler control in a bog garden because the water level is variable, so I needed to add drainage without delay. I hadn’t trimmed the black plastic lining along the edges and this was the main culprit stopping drainage. After cutting it to soil level the water could drain into the surrounding garden. I also added more soil to the wettest parts, leftover after filling the bog garden. This quickly soaked up the water and left the plants in saturated soil. This week’s rain has continued to soak the bog plants, but there’s no longer surface water.

the soil is still very wet, just right for the bog plants

Most bog gardens are connected to a pond. Winter overflow from the pond runs into a boggy area and as this soaks to capacity, excess water drains through our sandy soils. I chose my garden pond placement haphazardly around plants already growing. The lowest point of the lining overflows into a small section of the garden bed next to a lawn walkway. This would have been the perfect spot for the bog garden, except I need to walk through there. My bog garden section is on the other side of the lawn pathway. Perhaps in the future I’ll remove the lawn, build a footbridge and connect the pond with the bog garden. The perfect dream garden!

winter overflow from the pond

* White Cloud Mountain minnows are native to China and while likely extinct in the wild are widely available in the aquarium trade. A feral population of White Cloud Mountain minnows was found in NSW, most likely the result of fish being washed out of backyard ponds during heavy rains. My garden location isn’t prone to flooding, but in areas where this is a consideration, only native fish species should be stocked.

Reference

  1. Aplin, Piano & Sleep (2002) Building Frog Friendly Gardens. Western Australian Museum: Perth (p.40)

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