Don’t expect the “Weed Police” to knock on your door if you dig up a noxious weed and share it.

But a noxious weed technician with the Oregon Department of Agriculture says we all share a responsibility to watch out for these deceptive invaders just the same.

These invasive species can cause massive economic damage, impact recreation and harm agriculture.

“A weed can be any plant growing where you don’t want it,” says Beth Myers-Shenai, “but a noxious weed is any plant designated by the Oregon State Weed Board that is deemed injurious to public health, agriculture, recreation, wildlife or any pubic or private property.”

She works on weed control projects around the state trying to contain the most troublesome ones. She spends her time in winter managing the the WeedMapper database and website (www.weedmapper.org)

Besides providing maps of known infestations of the most serious weed pests in Oregon, the WeedMapper site contains detailed information on each weed with photographs to assist in identification.

Noxious weeds have caused $83 million in economic damage to Oregon lands alone and $27 billion nationally, Myers-Shenai says.

Weed designation

Noxious weeds and their control are classified with a designation of A, B or T.

n “A” weeds have no ecological importance and come in small enough infestations to make eradication/containment possible.

Infestations haven’t occurred here yet, but their presence in neighboring states makes future infestations in Oregon seem imminent.

These are high priority weeds and the state wants them gone from Oregon. Please call 1-866-INVADER if you suspect you have found any of these weeds.

n “B” weeds are weeds of ecological importance that are regionally abundant, but which may have limited distribution in some counties.

Gardeners are asked to stop sharing these plants and clip all seed heads. If you would like more information on how to control these weeds, please contact your local county weed program or extension agent, or refer to the Pacific Northwest Weed Management Handbook.

n “T” stands for target. Targeted weeds are a priority for eradication — those that represent an ecological threat to the state of Oregon — and are species that can come from either the A or B list. Please call 1-866-INVADER if you suspect you have found any of these weeds.

‘A’ weeds

Giant hogweed (Heracleum mantegazzianum), orange hawkweed (Heracium aurantiacum L.), and Paterson’s curse (Euchium plantagineum) are examples of “A” designated weeds that gardeners find favor with because they are pretty. However, don’t be fooled.

1. Giant hogweed is a public health hazard — causing dermatitis and blisters to the skin from exposure to the sap or smoke when burned (sounds like poison oak to me). This weed looks similar to Queen Anne’s Lace and cow parsnip but it is much taller. Queen Anne’s Lace comes in at a mere 2 feet, cow parsnip at 6 to 8 feet, whereas giant hogweed is a robust 10 to 15 feet. (The record is 20 feet!)

The leaf shape is also a bit different, but the stem of the giant hogweed is readily identified by its purple blotches and blistery stem. It is spread by people sharing it and from seeds scattered around the mother plant forming a colony. Seeds float down waterways to colonize elsewhere.

2. Orange hawkweed easily inhabits moist grasslands and forest openings. (Found only in a few places in Oregon so far.)

Gardeners find its brilliant orange color appealing but should beware. Its aggressive growth is derived from its ability to spread by rhizomes, stolons or seeds and its allelopathic compound (toxic substance) that practically eliminates all other vegetation around it in older stands.

Myers-Shenai said some nurseries are mistakenly selling this under different names. However, it is more often spread by trading plants or by seed caught in equipment and tires.

It is also easily spread by daughter plants much like strawberries have (above and below the surface) and by seeds that are light and can be blown a long way.

3. Paterson’s curse is an aggressive drought tolerant plant whose origin and spread was found in mixes of wild flower seed (adjacent to cropland in Linn County) and contaminated equipment or hay (pastureland in Douglas County).

The problem is its ability to generate rapid growth and produce a new crop of seeds within a few weeks of germination.

The plant also contains pyrrolizidine alkaloids similar to those found in tansy ragwort which cause chronic liver damage in livestock.

‘B’ weeds

The butterfly bush (Buddleja davidii), yellow flag iris (Iris pseudacorus), and garlic mustard (Alliaria petiolata) are examples of “B” weeds commonly traded by gardeners.

1. The butterfly bush can be found in nurseries if it is a named horticulture variety (like some ivy). It is liked because it is very attractive to beneficial insects like butterflies and bees and to most gardeners it does not appear to be a threat because it may not spread in their yard. However, if placed in its “comfort zone,” it can pose an ecological threat to dry-land meadows, open spaces and dunes. It also invades reforested sites, resulting in a loss of forest productivity. It can be spread by flood events and seeds.

2. Yellow flag iris displaces native plants including sedges and rushes along waterways including irrigation canals and flood control ditches. This can reduce the carrying capacity of wetlands for waterfowl and disrupt other ecological relationships. Removal is expensive and control in heavily infested areas can be cost prohibitive.

3. Brooms include Scotch, Spanish, French, and Portugese. Research and testing of bio-controls (plant specific natural predators) have come up with seed eating beetles and weevils whose larvae burrow into the seed pod so that the plant doesn’t mature.

(Side note: It is hard to tell the difference between brooms and gorse as they have similar pea-like flowers, but to help you, gorse has leaves that are spine-like and its oil is very volatile — and that is the reason Bandon burned down not once, but twice!)

‘T’ weeds

A “T” weed is one that we feel is worth the effort to spend time and money to control, i.e. there are still large areas of the state that have not been invaded by it, Myers-Shenai says.

But it has the potential to move to those places easily unless we put forth the effort to contain or eradicate it where it has invaded, she says. Targeted weeds in Oregon are a high priority to develop and implement a statewide management plans for. These weeds are species selected from both the A or B list.

1. Garlic mustard is a B and T weed that got started here as a culinary herb. Since then has been moved around by human movement most likely on tires or shoes. Its defense mechanism is an allelopathic compound that inhibits plants around it from growing. This weed is problematic in only a few pockets in Oregon — so far — the Columbia Gorge area around Corbett and in the West Hills of Portland where it has gotten a foothold in the forest understory as it likes shade or sun. There is also a small pocket in Jackson County along the Rouge River.

2. Purple loosestrife (Lythrum salicaria L.) is a B and T wetland shrub that’s vigorous growth crowds out marsh vegetation required by wildlife for food and shelter.

Weeds without the “T” designation either have already spread to most of their potential habitat in the state, do not have spread mechanisms to move quickly or easily, or, in the case of “A” weeds are not in the state yet, she noted.

Quarantine

Right now it takes a quarantine to regulate how a plant can be sold. A quarantine is established against any noxious weeds “A” or “B” listed by Oregon law — with few exceptions. Quarantined plants apply to whole plants, plant parts, and seeds. These are prohibited from being propagated, transported, purchased, or offered for sale in the State of Oregon.

Remember: Don’t unwittingly dig up a noxious weed — easily identified on the weedmapper website (www.weedmapper.org) — and sell it at plant sales or give it to friends.

The take home message Myers-Shenai wants to pass on is this: “Be responsible growers. Don’t trade or share suspect plants. And don’t put weeds like ivy or knotweed in your compost pile.”