A combination of special conditions sustains a bog. These include a high water table, lots of sunlight, a nutrient-poor soil, and most importantly, sphagnum moss.

 

Water levels are close to the surface during the winter when there is a large amount of rain. Excess water flows through the surface layers of the bog and out at the drain located near King Edward Avenue at the southeast corner.

Starting normally in late April or early May, the rainfall decreases so that evaporation is greater than precipitation and the water level starts to drop. This continues through the summer, until September or early October when the fall rains start. The level then rapidly rises as the bog is filled. From November onwards the water levels are generally high and fairly constant.
The critical time in the bog is late summer when water levels are at their lowest. In the core area of the bog this may be 50 or 60cm below the surface. On the periphery it may be much lower, as much as 100cm below the surface.

The existence of the bog depends on one plant, sphagnum moss. This thrives in soil of low oxygen content and with poor nutrient availability.
Its stems are hollow and it holds large amounts of water, helping to keep the water table close to the surface. It does not rot easily and the dead shoots remain attached to the living plant forming a giant "sponge". Thus the peat below the surface and the growing sphagnum may form continuous structures which can be hundreds of years old.
Sphagnum also acidifies water as it absorbs nutrients, and this makes decomposition still more difficult. Nutrients are locked up in the peat, which does not decompose, thus keeping the nutrient levels low. The only source of new nutrients is rainfall and this water is quite pure.

A bog is an open place with lots of sunlight, but with a very acid soil, low oxygen and low nutrient contents. Most plants cannot grow in these conditions. However a number of specialised plants including sundew, Labrador tea, and cloudberry, have evolved to take advantage of these special conditions where they have little competition from normal forest plants.
If conditions change, and bog plants are in competition with forest or marsh plants, then inevitably the bog plants die out. This is currently happening in Camosun Bog in areas that have not yet been restored