According to a council spokesperson, the plant is a native called Azolla and does not pose any harm to aquatic animals.

However, with the growth looking just like the lush grass surrounding the pond, the council has acknowledged it could pose some harm to the unwary or accident prone who may mistake the water for solid ground.

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This week, council workers fenced off the area near the regional children's playground with orange flags to prevent any runaway little ones from stepping out on the water.

The council's horticultural staff said Azolla was "very common in slow-moving waterways and ponds" but that this year's growth was the heaviest they have seen.

"This is likely attributed to very low rainfall in recent months reducing waterflow, combined with shallower warmer and nutrient-loaded water," a spokesperson said.

"The plant will turn red as it ages. We will continue to monitor the plant and the park. The plant is currently absorbing the high nutrient content in the water, which is likely preventing harmful algal blooms when the water levels are so low."

"Given the plant's growth, we will mark off the entire pond this week, and place signs warning the public."

The plant could continue to cover the Stuart Park pond throughout summer, they said.

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