Biological invasion by plants is a worldwide phenomenon and a leading cause of biodiversity loss, second only to the destruction of natural habitats.
Invasive plants are typically non-native plants that aggressively out-compete other vegetation. While all invasive plants can be considered weeds, not all weeds are equally invasive. Many “weeds” and non-native plants do not detrimentally affect native plant communities. Some aggressive native plants can act in an invasive manner in disturbed environments. When invasive, non-native species grow outside of their natural range and they are not controlled by the natural interactions of predators, parasites, diseases and competition from other plants. These plants have aggressive reproductive qualities such as rapid growth, abundant seed production, widespread seed dispersal and vigorous vegetative spreading. Invasive plants are highly adaptable and are able to tolerate a wide range of habitat conditions.
Invasive plants in Chelsea
Invasive plants are becoming more and more widespread in Chelsea and in the surrounding area. These unwelcome invaders are disrupting natural ecosystems, replacing and eliminating native species and reducing our region’s unique and diverse biological resources. Therefore, the identification and control of invasive species is of great importance.
If you see an invasive plant in Chelsea, please contact Martine Gauthier at 819-827-6227, to report your sighting. We are working on mapping local invasions in an attempt to better understand and control this problem.
For more information:
Dog-strangling vine (Cynanchum rossicum)
Dog-strangling vine (DSV), also known as pale swallowwort, belongs to the Milkweed family (Asclepiadaceae). It is a non-native perennial, twining vine from Eurasia. The vines can grow up to 2m in height, and have small pinkish to dark maroon flowers that start to appear in late May to early June. Opposite leaves are ovate, dark green, smooth, and shiny. The seed pods begin appearing in late June and are mature by mid to late July. Each pod produces numerous wind-borne silky-haired seeds.
DSV can reproduce by seed and by its massive underground root system (rhizomes). The seed is extremely viable once it germinates and the rhizomes can also propagate many new plants.
DSV grows well in the sun, the shade and all soil conditions, making it extremely difficult to control. The vines can form dense colonies, smothering short plants, and can grow over small shrubs and trees causing deformities and possibly death.
In some instances old-field habitats occupied by goldenrods and grasses are replaced almost exclusively by pale swallowwort, disrupting natural succession and completely altering the physical structure of those habitats.
Digging up the plants
Remove plants from the site and destroy them. Eradication on a small scale must be very thorough and requires dedication. The complete root crown must be dug out before the seeds ripen.
Ploughing and planting
Infested land might be brought under control by ploughing and planting an annual crop until the seed soil bank is depleted, possibly as long as five years.
Mowing and mulching
Mow the plants in mid to late June, when the pods are starting to appear, to help stop seed production. Covering the area with mulch helps to stop the sprouting of new plants from the rhizome.
The sap of this plant can cause an allergic reaction in some people.
Wear gloves when handling it and
wash exposed skin with soap afterward.
Disposal of the plants
For small infestations, seed pods and roots can be placed in paper bags to dry out, and then burned in a fire pit. Another method is to boil the seeds for at least ten minutes to ensure that they will never germinate. You can also store the seeds in water until they rot (several months). The rest of the plant, the stalk and leaves, can be composted.
For larger infestations, the seed pods and roots, or whole plants, can be placed in heavy-duty plastic garbage bags and kept until they can be safely burned in a fire pit. Another option is to add water to the garbage bags and leave them out in the sun for a few months. The resulting stew can then be disposed of safely in compost piles.
Green matter will not be picked up by the municipality during the collection of household waste. Dispose of it in a compost pile if possible, or keep it until late fall or winter when it can be burned safely in a fire pit.
You can bring your collected invasive plants that were dried for at least 1 week by the sun in paper bags at the municipal garage (119, Scott road) on Thursday, July 31 2014 from 3:00 pm to 6:00 pm. A biologist will be on site to collect.
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Giant Hogweed (Heracleum mantegazzianum)
Giant hogweed is a giant perennial and multiannual herbaceous plant (can reach five meters in height). This invasive exotic species in the Apiaceae family has a stout ridged and hollow stalk measuring 5 to 10 cm in diameter. The stem is covered with hard white hairs, mostly at the base of the leaflets. The leaves are deeply serrated, large (1 to 1.5 m and 2.5 m for basal leaves), dark green and divided into three broad irregular leaflets. The giant hogweed flowers from June to August. Its flowers are small (about 12 mm), greenish white and grouped in inflorescences formed by 4 to 12 umbels 20 to 150 cm in diameter. The mature fruits are light brown, elliptical flat-winged (or oval and hairy), and range from 6 to 18 mm long and 4 to 10 mm wide.
Each plant produces on average between 30,000 and 50,000 winged seeds (achenes), but some plants can produce up to 100,000 seeds. These oval and hairy achenes have the ability to stay viable 5 to 6 years in the soil, but some may remain viable for up to 15 years. They are transported by wind over short distances (8 to10 meters) or over long distances by streams and rivers. The large taproot (60 cm) allows growth and rapid regeneration of the plant when it is cut. This high productivity and ease of regeneration of the giant hogweed explains its colonization success. This mode of reproduction means that even one single plant has the capacity to establish a whole new colony.
Giant hogweed was introduced in an area mainly for horticultural purposes. We generally find it on private land where it often escapes to colonize other areas, such as embankments by shorelines, ditches, around railways and road encroachments. It can also grow in meadows, on vacant lots and on agricultural land.
This invasive species rapidly develops into very large colonies and threatens our native vegetation. It has recently appeared here in Quebec and has been spotted in several regions, stretching from the Outaouais, to Côte-Nord and the Lower St. Lawrence.
** WARNING **: The hairs and nodules found on the stem and leaves contain a milky, colorless, odorless and highly toxic sap that can cause severe irritation, burns and dermatitis.
The sap of the giant hogweed contains toxic chemicals activated by light, called furanocoumarins. Although the initial contact with the sap is painless, exposure to ultraviolet rays from the sun activates furanocoumarins and can cause serious burns sometimes called phytophotodermatitis. This skin disorder is characterized by redness and local swelling, followed by blistering that can stretch over several centimetres. The healing period usually takes one week, but the lesions often remain sensitive to the sun and leave dark spots, which can last several months afterwards.
It is therefore very important to protect yourself when handling giant hogweed, including covering all parts of your body and wearing eye protection.
Management of the plant
It is very important to limit the spread of the giant hogweed. Never sow, plant, multiply or transport it. Wherever possible, it is imperative to eliminate and destroy the plant’s regrowth.
Before digging it up, the following precautions need to be taken to avoid any exposure to the toxic sap:
- Cover all body parts with non-absorbent protective clothing (pants, long sleeves, and gloves with extended sleeves);
- Remove clothing and gloves by turning them inside out;
- Protect the eyes or all of the face (visor);
- Ensure that nobody is the range where they could be reached by sap droplets or plant debris;
- Use a knife or round shovel to cut the stems and roots;
- Wash all tools that have been in contact with the sap of the plant (pruning shears, clearing equipment, etc.).
Unearthing the plants
Remove all plants from the site and destroy them. If only the stalks are cut and the root survives, the plant can produce new shoots during the same year and the following year. It is important to cut the roots of these plants to a depth of about 20 cm below ground surface using a round shovel or knife with a rigid long handle to unearth it.
Ploughing and planting
A local infestation can be controlled by tilling to a depth of 24 cm and by planting an annual crop until the seed bank in the soil becomes exhausted.
Mow and sow
Cut the plants in mid-June to late August, 2 to 3 times per year over several years. Covering the affected area with mulch or sowing a mixture of grass will help prevent germination of new plants from the rhizomes.
Apply glyphosate or triclopyr on the leaves, or inject the product into the stems. Several applications will be necessary. A permit from the Municipality of Chelsea must be obtained prior to applying any type of herbicides.
Measures to be taken in case of exposure
When skin has been in contact with the sap, promptly remove all of the sap residue by sponging, to avoid spreading it to other parts of the body, wash using a mild soap then rinse thoroughly with water. Cover the affected areas to avoid exposure to light for a least 48 hours.
If any burning develops, avoid exposure to light for at least one week and use sunscreen lotion (minimum SPF 30) for the next six months.
If the eyes are affected, rinse thoroughly, wear sunglasses to prevent exposure to light and see a doctor immediately.
In any case, you should consult a doctor when:
- The eyes are affected;
- The person has a fever;
- The person has significant lesions (larger than a quarter);
- A child has been in contact with the plant.
For any information regarding the health effects and what to do in case of exposure to the sap of the giant hogweed, call Info-Santé at 8-1-1.
In order to dispose of plants that have been cut down, we generally recommend to dry them by placing them in sturdy plastic bags, sealing the bags and placing them in the sun for a minimum of one week.
Another option is to place the plants in paper bags and keep them until the fall or winter when they can be burned safely in an outdoor fire.
Organizations to contact for information
- Call Info-Santé (8-1-1) or contact your doctor
Issues regarding the spread of the plant
Information Centre of the Ministry of Sustainable Development, Environment and Parks
Report the presence of the plant
Network monitoring of invasive alien plants
Ministry of Sustainable Development, Environment and Parks
Municipality of Chelsea
- Isabelle Pitre, 819-827-6227
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