Invasive plants are spreading agressively across Gabriola and all of BC. The Invasive Plant Council of BC web site states: "Often mistaken for wildflowers, invasive plants are spreading through our natural ecosystems, urban landscapes, and agricultural lands at an alarming rate. Invasive plants are spread through several key pathways of invasion including increased international, national, and regional travel and trade; horticulture, gardening, and ornamentals; transportation and utility corridors; seed mixtures (re-revegetation, birdseed, wildflower); recreation; and wildlife, livestock, humans, and pets."
The four worst invasive plants on Gabriola are scotch broom (Cytisus scoparius) in open sunny places; daphne, or spurge laurel (Daphne laureola) in the forest understorey; tansy ragwort (Senecio jacobeae) in sunny spots and along roadsides; and giant hogweed (Heracleum mantegazzianum) in moist areas. Alarmingly, we now also have some scattered infestations of Japanese knotweed (Fallopia japonica), which is becoming a major problem in southern BC. Other invasives include some beloved plants like Himalayan blackberry, periwinkle, holly, ivy, and yellow flag iris, and familiar garden pests such as thistles. This page offer some advice on how to identify and safely remove a few of the worst invaders from public parks, roadsides, and our own land.
Scotch broom (Cytisus scoparius)
Scotch broom is a very invasive bush, common on highway shoulders, roadsides, abandoned logging trails, forest clearings and other open areas on Vancouver Island and the Gulf Islands. It matures into a strong shrub with main stems up to 7.5 cm in diameter. The flowers are pea-like, in bracts, usually yellow in wild Scotch broom. The twigs are green, hairless, and grooved. It will regrow from cut stumps if green bark is present and the cut is clean. After 10 years it begins to die but new generations of seedlings usually replace mature stands. Its seeds are distributed through our highway network by the tires of off-road vehicles and into isolated open areas by birds. It out-competes indigenous plants in reproducing, in taking over space, chemically inhibiting neighbouring vegetation, discouraging browsing, and holding viable seeds till the opportune moment to germinate arrive—sometimes decades later. Broom prefers acid soil and good drainage, but is not particular about soil fertility. It withstands drought. Here is a link to a pamphlet on Scotch broom published by the Invasive Species Council of BC.
Pull your own broom!
Wherever you see Scotch broom on public land (or your own!), do the whole island a favour and remove it before it goes to seed. In May and June it's easy to see because of its beautiful yellow blooms. GaLTT has special tools called Extractigators that help to pull larger plants up by the roots. There are two sizes, depending on the job. You may borrow one by calling Rob Brockley at 250-247-9467. When you pull broom, tamp the soil down afterwards to avoid light getting to seeds in the soil.
Gabriola's regular broom-bashing
Each May, dozens of enthusiastic broom-bashers (volunteers from GaLTT and the Lions Club) meet regularly at Drumbeg Park to continue the major (ongoing) task of pulling out invasive Scotch broom which threatened to overtake the Camas meadow. It's always a pleasure to see the lovely spread of blue Camas lilies (Camassia quamash) and yellow Spring Gold (Lomatium utriculatum) blooming on the broom-free meadow. Also, a few garry oak (Quercus garryana) seedlings can be found in the grass where broom was pulled over the last few years. New broom seedlings are there too though, so it's a constant battle.
Joanne Sales from Nanaimo Broombusters gave Gabriola's Gardening Club this advice in April 2013: Main message—It's best to cut the broom while it is flowering and before it goes to seed.
Mature broom in full bloom (April to June)
Use geared loppers to cut as close to the ground as possible.
Pile on other invasives such as blackberry, or put through chipper.
Mature broom in full bloom with seedpods (July to August)
Use geared loppers and cut close to the ground, but this is NOT a good time to cut in most places because of the danger of spreading seeds.
If you cut, try to catch the seeds and destroy them. Avoid spreading them.
Mature green broom the rest of the year
Pull with Extractigators. Pull grass back over the exposed dirt to prevent light reaching seeds in the soil.
Lopping can produce fan-shaped plants that are more difficult to pull later.
Place broom without seedpods in piles or use a chipper. Dry broom is a fire hazard.
Small seedlings in wet periods
Hand pull and tamp down bare or disturbed soil.
Disperse on ground or place in piles.
Small seedlings in dry conditions or where hand-pulling is difficult.
Use small "Junior" Extractigators and tamp down bare or disturbed soil.
Disperse on ground or place in piles.
Medium sized green broom that's unlikely to bloom.
Use either size of Extractigator but take care to tamp down disturbed soil and cover with grass.
Place on piles or over other invasives such as blackberry.
Mature broom trees
Saw down at any time.
Probably best left where it falls.
Daphne or spurge laurel (Daphne laureola)
Daphne (spurge laurel) is spreading very rapidly through the understorey of Gabriola's forests. Because of its attractive "waxy" blue-green evergreen foliage, it is still sometimes sold as an ornamental shrub and has only recently become recognised as a serious pest. It bears its inconspicuous clusters of yellowish-white flowers very early in the spring, followed by black berries, which are spread by birds and rodents. All parts of the plants are somewhat toxic, but some people are more sensitive to the toxin than others.
To remove daphne, use gloves and try to pull it up from the roots. If you snip small plants, they will continue to grow and branch into a sturdy bush, but if a large plant has all its branches snipped off in late summer, the stress may be enough to kill it.
Pulling large daphne is best done with a tool called an extractigator—Rob Brockley says "you can borrow a GaLTT extractigator at no charge… just give me a call at 250-247-9467."
Do NOT burn removed plants—it releases too many toxins.
Do NOT add them to a residential compost pile if the compost will be used on a vegetable bed.
Seal the plants in dark plastic bags and leave them in the sun to "bake", then put the bag in the landfill or a large composting facility where its toxicity would be much diluted. BC Parks personnel have recently experimented with piling culled daphne on top of other invasive species such as periwinkle to kill them also.
The Commons team has done sterling work pulling invasive Daphne laureola from their land, some of it really large. And they've discovered an added problem—horizontal branches can put down new roots and then send up a new shoot, as you can see in Don Smardon's photo at right.
For more pictures and advice on managing invasive Daphne laureola click here.
Tansy ragwort (Senecio jacobeae)
Invasive tansy ragwort is sreading rapidly on Gabriola, Mudge and Valdes Islands, and blooms from July to September. The plant has clusters of bright yellow daisy-like flowers, is about half a metre tall and has deeply lobed bright green leaves. A single ragwort plant can produce 150 thousand seeds! Here is a link to a pamphlet on Tansy ragwort published by the Invasive Species Council of BC.
Help eradicate it by uprooting and removing the plants before they go to seed. Use protective gloves and make sure you pull out all the root system so that it doesn't regenerate. Bag the culled plants for removal. Do NOT leave the pulled plants on the ground where animals could eat them. They are toxic to cows, horses, and even goats.
A great way to deal with culled tansy ragwort plants is to just stuff them into a black plastic garbage bag and seal it. Leave them to compost in the sealed bag for a few months (to make sure no seeds escape) and you'll get some good, pest-free soil for your garden.
Tansy ragwort does have one good natural enemy—the caterpillar of the cinnabar moth. So if you see any on the ragwort, don't kill them—leave them nearby to feed on any plants you miss.
Giant hogweed (Heracleum mantegazzianum)
Giant hogweed (also known as giant cow-parsnip) is an aggressive invader that was introduced as a garden ornamental. It resembles native cow parsnip but is much larger. It can grow to 6 metres. It is adapted to moist areas, competing with native plants and causing riparian damage by erosion with its shallow root system.
It spreads easily and is hard to eradicate. It reproduces by seeds and from perennial buds at its crown. The seeds are adundant and long-lasting in the soil.
This plant is a persistent problem in Drumbeg Park in the fenced area behind the public toilets, and can be found elsewhere on Gabriola.
Here is a link to a pamphlet on Giant hogweed published by the Invasive Species Council of BC.
WARNING—DO NOT HANDLE THIS PLANT!
Its sap on exposed skin causes hypersensitivity to sunlight, resulting in blistering and dermatitis. Scarring and blindness may result.
Management strategy: Use protective clothing and eyewear. Cut off the flowerheads to prevent seed formation. Excavate the plants by severing the roots at least 8 cm below the soil surface. Dispose of plants in strong garbage bags. DO NOT COMPOST. Return to the site to check for regrowth—followup may be needed for 3 to 5 years.
Chemical controls can be effective using foliar application in both spring and summer, or stem injection during heavy sap flow in spring.
Japanese knotweed (Fallopia japonica)
Knotweeds are among the top ten invasive species listed for eradication in BC. They are native to Asia and were introduced to BC as an ornamental plant. Four species are currently found in BC: Japanese knotweed (Fallopia japonica)—the most common, Giant knotweed (Fallopia sachalenensis), Bohemian knotweed (Fallopia x bohemica), and Himalayan knotweed (Polygonum polystachyum). They are similar in appearance, biology, impacts, and distribution. The leaves of Japanese knotweed (shown at right) are heart shaped and rather like lilac. All the knotweeds have extensive, strong root systems, and stalks rather like bamboo. Here is a link to a pamphlet on knotweeds published by the Invasive Species Council of BC.
Knotweeds reproduce through their roots and stems ("vegetatively"). Once established, they can grow through concrete and are extremely difficult to eradicate. Grazing and cutting must be repeated frequently and over many years to be effective. Usually herbicides are required for eradication.
Pamela Wesley's list of invasives
GaLTT was fortunate to have Pamela Wesley, MSc, Extension and Outreach Coordinator, Coastal Invasive Plant Committee (CIPC) to address the 2009 AGM on the topic of "Managing Invasive Plants on Gabriola Island." You can click the button at left to link to CIPC's website, or phone them at 250-857-2472, or email them. The following list of invasive plants on Gabriola was prepared by Ms Wesley.
Invasive plants reported to be on Gabriola Island
Locations & comments
Drumbeg Pk. Sandwell Pk.
Drumbeg Pk., Gabriola Sands Pk. (Twin Beaches)
(aka morning glory)
Orlebar Pt., South Rd., Martin & Sir William Drive, in
& NE of Drumbeg Pk.
Bertha at Suzanne
Gabriola Sands Pk., Cooper at South near Degnen Bay
Beside roads and in parks
Drumbeg Pk., Gabriola Sands Pk.
Some major infestations
Horseshoe Rd., Bell's Landing
Gabriola Sands & Sandwell Pks., Degnen Bay, Stalker Rd., Whalebone Dr.
Some major infestations
Yellow flag iris*
Descanso Bay & Valley; South Rd., Fenwick, Windecker
* = CIPC priority species
The slides Ms Wesley presented including photos of the plants and suggested means of control are in two downloadable pdf files (about 4GB each): Part I and Part II. Many of these images have copyrights associated with them so should not be copied without permission.