Noxious weeds are plants that have been introduced to our region from other parts of the world. I make a distinction between introduced species, which, even though they are introduced they typically are not aggressively outcompeting native vegetation. You won't find dandelions, chicory, or even clover on this page. This page is concerned with noxious introduced species which threaten the native biodiversity because they are aggressive and have no/little natural enemies. Introduced weeds will be found on the other pages on this site according to their species for the purpose of identification, they are always noted as being Introduced species.
What Can We Do About Noxious Weeds?
A NOTE OF CAUTION: Be sure you have a positive identification and are not removing a similar looking native species. Noxious weeds tend to be dissimilar enough that this is usually not a problem, however when specimens are young and/or not in bloom it can be difficult to distinguish some plants.
1. Early detection and removal. If there are few plants then remove them, leave in place if the seeds have not developed yet, or remove in a bag if in bloom.
2. Manual Removal - Remove by cutting at the base this will only kill some plants and usually only when drought-stressed. Then use grazing goats to kill off emerging sprouts, this will need to be done for a period of a couple months at least for most weeds, and for some you will need to periodically remove more plants as seeds can be "banked" in the soil for up to 30 years in the case of Scotch Broom for example. Plastic Mulches can be used in small localized areas to kill off emerging sprouts. Fire can be used for some species but may encourage further germination in others, and may be difficult to control.
3. Do Not Grow Noxious Weeds on Your Property or allow them to grow where it is possible to eliminate them (ie: don't assault your lawn with chemicals to remove the dandelions but do manually remove the scotch broom or Himilayan blackberry and then replant native vegetation).
4. Re-sow or Re-plant with Native Vegetation upon removal of noxious weeds and in any recently cleared or disturbed areas, monitor sites periodically long after removal to ensure there were none that were missed or banked in the soil. This will prevent future infestations from becoming established and the native wildlife populations will thank you!
5. Track and Report the Movement of Noxious Weeds in your area, particularly where entering sensitive habitats such as forests, wetlands, etc.
6. Join Weed Warriors on the Sunshine Coast, a new volunteer based noxious weed removal group being created right now. For the first few years I plan to focus on Scotch Broom and Japanese Knotweed If you are on Vancouver Island check out Broombusters if you would like to volunteer in a volunteer Broom removal project going on there.
Himilayan & Evergreen Blackberries
Rubus discolor & R. laciniatus
Description: Spiny, trailing, arching (erect when short0 stems to 10m long, often rooting at the ends forming new plants. Covered with curved prickles. Alternate evergreen/ deciduous leaves are trifoliate, or 5 - foliate with 10-25cm wide oval leaflets. (Outer & background leaves in the picture) R. laciniatus is the Evergreen Blackberry shown in foreground and center) with much more deeply and jaggedly toothed leaves that are more purplish on the tops but greenish underneath. It grows in similar conditions with the Himilayan. Both produce large 1-2cm berries that are sweet and delicious.
Ecology: Grows at low elevations in disturbed sites and streamside areas. Often in recently cleared and disturbed sites. Very abundant.
Notes & Remediation: This introduced invasive shrub has become widely naturalized, often competing with native shrubs such as the salmonberry, thimbleberry, wild raspberries and others. This weed is very difficult to remove as it has very tough roots that are difficult to remove. This picture was taken next to a sidewalk in Gibsons, BC. While it is a noxious weed, much of our wildlife has adapted to feed on the blackberries as a food source. The problem is however that the blackberry reduces biodiversity due to competition and this results in a less varied and therefore less nutritious diet for our native wildlife.
Do not allow this weed to grow in your yard; where you see a small plant getting established somewhere destroy it and prevent it from becoming a permanent resident. The plant must be removed by the roots, and all of the roots, care must be taken to get all runners that have also rooted.
Scotch Broom
Cystisus scoparius
Description: Deciduous unarmed spindly shrub of the pea family, grows to 3m tall. Typical yellow pea flowers with a strong sweet fragrance. Produces black pea like seed pods to 5cm long containing numerous seeds, in the summer on a warm day you can often hear them popping open, sometimes hundreds at a time, depending on where you are. The seeds remain viable for up to 40 years in the soil making this weed very difficult to control once it spreads into an area.
Ecology: Grows in dry, open and disturbed sites. Widely abundant on roadsides and power lines throughout southern coastal BC. It's range is still expanding in our region.
Notes: This shrub was introduced from 3 original plants brought to Vancouver Island in 1850 by a Scottish immigrant. Now Scotch Broom has covered Vancouver Island and the Sunshine Coast, as well as the lower mainland. In May and June on the Sunshine Coast roadsides, power lines and empty lots literally look like a sea of yellow. Obviously this has resulted in severe competition with native species. This threat is particularly severe for rainshadow flora in the rare Coastal Douglas Fir ecosystem that occurs only in heavily developed areas such as Southern Vancouver Island, Nanaimo area and the Gulf Islands. Scotch Broom is a serious noxious weed with absolutely no benefit for native wildlife which do not feed on any part of the plant. Only aggressive, long term measures will help control this weed.
Remediation: All new plants seen establishing an area should be disposed of immediately. Large plants should be cut down before it goes to seed, pruning shears, or sometimes a small saw, will be necessary. Repeat removals from the same site in subsequent years will be necessary as the seeds remain viable for long periods of time Eventually native vegetation will grow up, this should be encouraged by planting native species that would have grown in the area originally before the land was cleared. Other alternatives include introducing a beetle species that feeds exclusively on the broom seeds. This is currently being experimented with in Washington State. The bottom picture is of my son who cut down and burned the broom at the last rental home we lived in.
For information on volunteering for broom removal on Vancouver Island check out www.broombusters.org, I hope to start a Sunshine Coast chapter/version of Broombusters sometime this year (2006), if you live on the Sunshine Coast and would like to assist me then please contact me or see Weed Warriors on the Non-Profit page for more information.
Gorse
Ulex europaeus
Description: Spiny deciduous shrub of the pea family with angled, hairy branches, it grows to 3m tall. Alternate 3 leaflets on young plants turn into the spines seen on mature plants. Typical yellow pea flowers smell like coconut and turn brown with age.
Ecology: Grows in dry, open and disturbed sites close to the ocean and human disturbance. Often found growing alongside of Scotch Broom, which it often is mistaken for at first glance due to its shrubby growth and yellow pea flowers, the two are easily differentiated however by gorse's abundant spines covering all of its branches, Broom is unarmed.
Notes & Remediation: This spiny shrub comes from Europe and can be very invasive once established. The good news is that unlike Scotch Broom seeds Gorse seeds only last about 3 years in the soil making small populations relatively easily removed using mechanical means followed by grazing or weeding as sprouts appear over the next 3-5 years. This picture was taken in Sechelt BC in an empty lot where it is starting to spread up the highway, if caught now this population could be prevented from spreading.
Hedge Bindweed
Convolvulus sepium
Description: A rhizomatous perennial with twining stems that form a hedge-like growth over other vegetation. It has 4-6cm arrowhead shaped leaves and large showy white or pinkish flowers that are 4-7cm long.
Ecology: Prefers moist and wet habitats, roadsides, thickets, disturbed areas, yards, etc. Often found growing with Himilayan blackberry and other noxious weeds.
Notes & Remediation: A pernicious weed that is very difficult to eradicate once established due to its deep, spreading rhizomes. It can choke out native vegetation and compete with those that remain for nutrients. Remove by carefully digging its rhizomes out of the soil, if the area is a disturbed or cleared site you can also try solarizing it with black plastic mulches. This picture was taken in the ditch outside of my house in Sechelt, BC, July 2001.
Japanese Knotweed AKA False Bamboo
Polygonum cuspidatum
Description: Large (1-3m) herbaceous perennial with erect or somewhat descending branches on leafy hollow cane or bamboo like stems. Egg shaped leaves are somewhat squared off at the base and are pointy at the tips. Produces numerous tiny whitish flowers in small panicles in the upper leaf axils.
Ecology: Found in moist ditches and waste places, disturbed areas around human settlements, often populations start from people throwing out their yard refuse in the local empty lot where it takes root and spreads. Still spreading in our area, has not even come close to reaching the full range of where it can grow.
Notes & Remediation: Can be confused with Giant Knotweed P. sachalinense but those leaves are less pointy a the tips and are more heart shaped and it grows to 4m tall. Himilayan Knotweed P. polystachyum has oblong lance to egg shaped leaves that are typically heart shaped with 2 small lobes at the base. All 3 species have been found growing in our area outside of gardens where they originated. All 3 species are to be considered noxious weeds and should be eradicated, all 3 species have been found growing in our area. This is an EXTREMELY noxious weed in our area, it has now spread all up the highway on the sunshine coast, it grows everywhere and is even out-competing broom and occasionally competes with Himilayan Blackberry. If you have it growing in your garden, please, please do not allow it to grow as it spreads aggressively. Dig it out by its roots and burn it. DO NOT dump it anywhere, I have found so many populations in the wild resulting from people cutting them out of their gardens (because it is so aggressive) and dumping them up various logging roads where the locals dump their yard refuse. Separate your yard refuse, any noxious species should always be burned or disposed of at a garbage dump, to prevent the spread of noxious weeds. See Weed Warriors on the Non-Profit page for information on a Sunshine Coast based volunteer noxious weed removal group being organized by Lyrae to remove Broom and Knotweed from the roadsides all up and down the Sunshine Coast.
Holly
Ilex sp.
Description: Shrub or small tree with smooth grey bark, white wood. Leaves are evergreen, very glossy green and leathery with undulate margins and spiny teeth. Staminate and pistillate flowers typically on separate plants, produces berry-like drupes, red in clusters that persist through the winter.
Ecology: Typically found in yards and gardens but has now escaped into the forests in southern coastal BC.
Notes & Remediation: Introduced from Europe as a garden ornamental but has now escaped and spread. While it is not overly aggressive it should still be considered a noxious weed because it is able to escape into the forest where small trees and shrubs are often found growing under the canopy of the forest where they will sprout up into a larger tree when a gap opens in the forest. Because it is able to penetrate the forest canopy if you have it growing in your yard, especially if you live on the edge of a park, waterway, or forest you should cut it down and plant native species instead.
English Ivy
Hedera helix
Description: Spreading vine from thin brown semi-woody trailing stems. Leaves are shiny dark green, evergreen and 3 lobed. Different varieties of English Ivy may have smaller leaves or variegated (dark green and pale green). Stems root where they land on the ground and will climb buildings, trees, etc.
Ecology: Widely used as a garden ornamental, smaller varieties often used in hanging baskets. Has readily naturalized in all forested areas near human habitation. Trailing stems will root where they land on the ground and will climb buildings, trees, etc doing significant damage to buildings and choking out and the trees they infest will eventually be choked out by the ivy and killed.
Notes & Remediation: English Ivy is quite hardy and will grow in a large variety of environments. It has infested large sections of forest in residential areas and vacant lots throughout southern BC. Once established it can be difficult to get rid of. Remove all ivy growing at the base of trees, pulling out the root from the ground and all the roots growing into the bark of the tree. Badly infested trees (up into the canopy) may / may not be salvageable and would have to be climbed in an attempt to pull the roots out of the bark. On the ground rip out all plants buy their roots. If nothing else is growing in the area it is good to kill any rooting pieces with black plastic for at least 3 months. Otherwise, check the area periodically and remove all new plants that take root. Do not purchase hanging baskets with ivy in them, and educate your friends and neighbours, some of whom may still think it is 'cute' to let the ivy grow up their cedar and fir trees in their yards not knowing that this practice will definitely kill the tree.
