De­cep­tively dan­ger­ous weed

The Glengarry News - - The Opinion Page -

Knowl­edge is power when it comes to deal­ing with nox­ious weeds such as wild parsnip.

Wild parsnip (Pasti­naca sativa) is an invasive plant na­tive to Europe and Asia. It was likely brought to North America by Euro­pean set­tlers, who grew it for its ed­i­ble root. Since its in­tro­duc­tion, wild parsnip has es­caped from cul­ti­vated gar­dens and spread across the con­ti­nent.

Wild parsnip, which is also known as poison parsnip, is a mem­ber of the car­rot/pars­ley fam­ily. It typ­i­cally grows a low, spindly rosette of leaves in the first year while the root de­vel­ops. In the sec­ond year it flow­ers on a tall stalk and then dies. The plant can form dense stands and spreads quickly in dis­turbed ar­eas such as aban­doned yards, waste dumps, mead­ows, open fields, road­sides and rail­way em­bank­ments. Its seeds are eas­ily dis­persed by wind and wa­ter, and on mow­ing or other equip­ment.

Like gi­ant hog­weed and other mem­bers of the car­rot fam­ily, it pro­duces sap con­tain­ing chem­i­cals that can cause hu­man skin to re­act to sun­light, re­sult­ing in in­tense burns, rashes or blis­ters.

In North America, scat­tered wild parsnip pop­u­la­tions are found from British Columbia to Cal­i­for­nia, and from On­tario to Florida. It has been re­ported in all provinces and ter­ri­to­ries of Canada ex­cept Nu­navut. The plant is cur­rently found through­out eastern and south­ern On­tario, and re­searchers be­lieve it is spread­ing from east to west across the province.

Flow­ers grow in yel­low­ish-green clus­ters.

Im­pacts of wild parsnip

The plant can form dense stands that out­com­pete na­tive plants, re­duc­ing bio­di­ver­sity.

Stem, leaves, and flow­ers con­tain chem­i­cals that can in­crease skin sen­si­tiv­ity to sun­light and cause se­vere der­mati­tis.

Wild parsnip re­duces the qual­ity and saleabil­ity of agri­cul­tural for­age crops such as hay, oats, and al­falfa.

Chem­i­cal com­pounds in the plant are known to re­duce weight gain and fer­til­ity in live­stock that eat it.

How to iden­tify wild parsnip

Grow­ing up to 1.5 me­tres tall, the sin­gle green stem is two to five cen­time­tres thick and smooth with few hairs.

Com­pound leaves are ar­ranged in pairs, with sharply toothed leaflets that are shaped like a mit­ten.

Yel­low­ish green flow­ers form umbrella-shaped clus­ters 10 to 20 cen­time­tres across.

Seeds are flat and round.

What to do

If you have small clus­ters of wild parsnip on your prop­erty (fewer than 100 plants), you may be able to man­age the plant your­self. Wear pro­tec­tive cloth­ing and dis­pose of plants care­fully, as de­scribed be­low. To re­move larger in­fes­ta­tions (thou­sands of plants), you will likely need a pro­fes­sional ex­ter­mi­na­tor and re­peated treat­ments over sev­eral years.

Wear pro­tec­tive cloth­ing, in­clud­ing water­proof gloves, longsleeve­d shirts, pants and eye pro­tec­tion. A dis­pos­able spray suit over your nor­mal cloth­ing pro­vides the best pro­tec­tion. Spray suits are com­mer­cial-grade water­proof cov­er­alls. Af­ter work­ing around the plant, re­move your pro­tec­tive cloth­ing care­fully to avoid trans­fer­ring any sap from your cloth­ing onto your skin. Wash your rub­ber gloves with soap and wa­ter, then take off your spray suit or outer cloth­ing. Wash your rub­ber gloves again and then take them off. Fi­nally, take off your pro­tec­tive eye wear. Put nondis­pos­able cloth­ing in the laun­dry and wash your­self im­me­di­ately with soap and wa­ter.

For a small in­fes­ta­tion in a yard or gar­den (fewer than 100 plants), dig out as much of the tap­root as you can with a sharp shovel or spade. Dig­ging is most ef­fec­tive in the spring when the soil is moist and the tap­root is more eas­ily re­moved. Fol­low-up dig­ging will be re­quired every few weeks to deal with re-growth (if the tap­root was not com­pletely re­moved) or missed plants.

An­other method of con­trol is to cover the dug or mowed ar­eas with black plas­tic to smother new growth of all plants.

HARDY NEME­SIS: Poison parsnip, which can cause se­vere skin dam­age, con­tin­ues to spread across ru­ral ar­eas.

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