Aquatic vegetation is an important part of the biology of Osoyoos Lake. However, many non-native plants have been introduced into the lake in recent decades, and they have become (or are potentially) extremely invasive.  Aquatic invasive weeds grow and spread rapidly, choking out native plants, impeding recreation and competing for oxygen in the water.  Many of the weeds listed below are found in aquariums and ornamental water gardens, and this may often be how they are introduced into the lake.

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How can you help control these weeds?

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•  Learn to identify aquatic weed species.

•  Clear all plant material from watercraft and accessories, then wash with hot water.

•  Don’t dump unwanted aquarium contents into storm drains, streams or the lake!  Dispose of plants far away from bodies of water.

•  Make others aware of the danger of these weeds.

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Species of Concern

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• Eurasian Milfoil (Myriophyllum spicatum):  Milfoil is an aquatic weed that was originally an aquarium plant. It is highly prevalent in Osoyoos Lake, and milfoil has been the greatest aquatic invasive plant concern in the Okanagan Valley watershed for many decades. Milfoil is highly invasive, spread by watercraft and trailers; even tiny fragments can take root easily. Effective methods of control have not been found yet.   
   

• Blue-Green Algae (Cyanobacteria): This is not actually a weed, but it is a concern in Osoyoos Lake. Simple one-cell organisms or bacteria, cyanobacteria need light to reproduce and survive. They thrive in warm, shallow, slow-moving water. A small amount in a lake is healthy: however, large amounts, as often occur in hot summer months, block out light and use up oxygen in the water, inhibiting plant growth.  Osoyoos Lake has large amounts of algae due to high nutrient levels in the water.
   

• Purple Loosestrife (Lythrum salicaria): Loosestrife is an ornamental plant, originally used by beekeepers. It spreads quickly along roads, canals, drainage ditches and wetlands. Stems can grow to over two metres, with purple flowers that can produce up nearly three million seeds each.  Loosestrife is invasive and widely established; it has been seen near the Channel Parkway in Penticton and other low-lying areas.  It can can be mechanically controlled to a certain extent, but it is almost impossible to get rid of completely – it just keeps coming back!
   

• Brazilian Elodea (Egeria densa): Originally an aquarium plant, it is related to the Hydrilla. Elodea will choke out everything else that grows in the water (including milfoil!), forming a dense green mat, and it is resistant to known treatments. Elodea has not yet been found in Osoyoos Lake.

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