What’s that plant flowering in the pond? It seems so healthy and abundant, yet you can’t remember planting it there. Gradually, the plant seems to sprout up everywhere around the pond and you realize that it is an invasive flowering weed. These plants may be sold in nurseries, but they can easily take over the pond ecosystem.
Water Hyacinth is a Pretty Purple Pond Invader
Water hyacinth (Eichhornia crassipes) is a beautiful weed that has become naturalized in much of the southern United States. It is originally from South America. Water hyacinth has lavender flowers on a long stalk. The plant can grow to be 3 feet tall, and it has dark green leaves and a thick, branched root system under the water. This makes it difficult to remove water hyacinth. In a large pond, it is quite possible for the leaves of the water hyacinth to cover the entire surface of the water. Cold water, salty water, and fast-moving water are all unpleasant environments for the water hyacinth.
Purple Loosestrife Spreads With Roots and Seeds
Purple Loosestrife (Lythrum salicaria) is a very invasive weed throughout much of North America. It originated in Europe and came to North American in the 1800s. From a distance, purple loosestrife is beautiful. It has somewhat heart-shaped leaves and has bright purple flowers on a spike, similar to foxgloves (Digitalis spp). Unfortunately, loosestrife is excellent at reproducing and each plant will create millions of seeds every year. The seeds are tiny and spread on the wind and water, while the roots of the plant create a mat that prevents other plants from growing. Hand-digging or cutting the flowers of the plants in the summer before they set seed is one way to control purple loosestrife. Bag the plants well so that you do not accidentally spread seeds to other areas.
Flowering Rush is an Invasive Plant Sold in Garden Stores
Flowering rush (Butomus umbellatus) is a popular ornamental plant that easily turns invasive. It produces umbrella-shaped groups of pinkish-white flowers. The leaves are long and narrow, with tips that grow into a spiral.
Flowering rush is a successful invader because it produces many seeds and also reproduces from broken rhizomes. It is very successful at colonizing disturbed areas. It can displace other shoreline plants like willows and cattails because its roots form a thick mat. It is difficult to remove flowering rush because any pieces of root that are left behind can make new plants. Cutting the flower stalk limits its spread.
Preventing the Spread of Invasive Pond Weeds
The best way to prevent invasive pond weeds from spreading is to avoid planting them in your garden. Many invasive species are sold as decorative plants in nurseries. Choose native plants for your pond or water garden or research a plant before you buy it to ensure that it will not take over the pond and surrounding native wetlands.
Tricia Edgar - Tricia Edgar is a gardener, environmental educator, and science writer from the Pacific Northwest.
