by Sherry Lyons
To continue the conversation about invasive species, I will move on to spotted knapweed (Centaurea biebersteinii DC). This plant grows up to five feet tall and has lovely purple flowers that look like thistle flowers. It is currently found in all contiguous 48 states and Canada, and it is highly invasive. Like many other invasive plants, it crowds out native plants with its monoculture. One of the ways it does this is by producing a chemical that is toxic to other plants, allowing it to spread rapidly. This also makes it irritating to the skin if one tries to pull it out, though that is one way to get rid of small areas of growth. It also has a symbiotic relationship with a fungus in the soil, which makes it possible to outcompete grasses. It also increases erosion and stream sedimentation. Mowing it before the flowers go to seed can limit its spread, although plants can also bud from the root crown.
Phragmites (Phragmites australis) are another very invasive plant that are detrimental to marshland just like purple loosestrife. If you have any areas on your property that are consistently wet, you may see this plant take over where cattails normally grow. Their roots can grow up to nine feet deep, with the stems growing over 12 feet high. It is almost impossible to eradicate, and it has actually broken through pavement, much like japanese knotweed. Many salt marsh bird species, amphibians, and reptiles that depend on other native grasses are declining as phragmite takes over. It supports fewer insects that birds depend on. The plants consume a lot of water, and the dead plant matter can clog waterways which impedes fish travel upstream to lakes to breed. Dense stands can make it difficult for people to reach water for recreational use.
However, there is a silver lining to the invasion of this plant. Its dense stands are also proof against storm surges and astronomical high tides, and it outperforms native grasses when considered as a carbon sink. It can also absorb nitrogen from the water, which can check algal blooms. Its roots allow it to hold soil better than other grasses, helping prevent coastal erosion. There are also native phragmites that do not cause problems because they are smaller, occur in more biodiverse areas, and support native wildlife.
The final plant for today is burning bush (Euonymus Alatus). Named for its bright red leaves in the fall, as Beth told us at the last meeting, it is highly invasive. Native to eastern Asia, it was brought here because of its beauty and quick growing habit, making it a good privacy screen. However, like many invasives, it spreads quickly. “Burning bush is tolerant of shade and adaptable in different soils, so it quickly outcompetes native plants in our forests. Dense thickets quickly form. Nothing else stands a chance, not even the future oak and pine saplings.” Burning Bush: the Good, the Bad, and the Ugly It does not host any native caterpillars, so it does not support any of our native bird species. The birds will eat the fruit and then dispose of the seeds the natural way in the woods, thus spreading euonymus everywhere. However, even though the birds will eat the fruit, it is not a healthy food source for them, not enough protein. It is now illegal to sell burning bush in Massachusetts, which may tell you how serious this is.
I hope this information is helpful to you. I know that after Beth’s talk last month, I went home and got out my loppers, my clippers, and my bottle of Round Up. I know I shouldn’t have been cutting them, because they were covered with seeds, but I used glyphosate on all the cut stems and pulled up a ton of baby burning bush that were too young for seeds. They were everywhere in one stretch of woods, once I started looking. I also cut back some bittersweet and multi-flora rose. Now that you know what these invasives look like, you can work on removing them from your property too. Every little bit helps!
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