Giant hogweed vs cow parsley vs hemlock: telling the umbellifers apart
Three white-flowered umbellifers — one is harmless, one is toxic, one will burn you. Here is how to know which is which.
Three white-flowered umbellifer species cause most of the misidentification calls we get every May. Two are British natives, one is an invasive nightmare. The good news is the differences are obvious once you know what to look at.
Cow parsley (Anthriscus sylvestris)
Native, harmless, knee-to-waist height, very common in May hedgerows. Leaves are fine and ferny; stem is smooth, hollow and a clean green. Flowers are small, white, in flat-topped umbels.
Hemlock (Conium maculatum)
Native, deeply toxic if eaten, up to 2 metres. The defining feature is the smooth stem with distinct purple blotches and a foul, mousy smell when crushed. Don't eat it; it will not burn you on contact.
Giant hogweed (Heracleum mantegazzianum)
Invasive, dangerous, up to 5 metres. Stems are 5–10 cm thick, bristly with coarse purple hairs. Leaves are vast — often over a metre across. Flower heads can be 60 cm in diameter. Sap causes severe phytophotodermatitis on contact with skin and sunlight.
Frequently asked questions
- How quickly do giant hogweed burns appear?
- Reddening can start within 15 minutes of UV exposure to sap-contaminated skin; full blistering develops over 24–48 hours.
- Is cow parsley dangerous?
- No. Cow parsley is a harmless native and an important food plant for many insects. It is, however, easy to confuse with hemlock at a quick glance — never forage from the umbellifer family without expert guidance.
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The survey team
PCA-certificated surveyors, Japanese Knotweed Elimination
PA1 / PA6A certificated surveyors who carry out the site visits, write the management plans and sign off the reports issued to lenders and solicitors.
Reviews the technical, legal and lender statements in this article.
What this page can't tell you
- Guidance is general. Identification, treatment choice and timescales can only be confirmed by a site visit — photographs alone are indicative.
- Lender and insurer requirements vary by institution and change over time. We state what is typically accepted, not what any named lender will accept on your case.
- Guarantee (IBG) eligibility depends on the plan chosen, the survey findings and the underwriter's acceptance. It is not automatic.
- Legal points summarise published law and guidance current at the review date. They are not legal advice.
Last reviewed · Questions on anything stated here: 07582 869979
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