Difference between cow parsley, hogweed and giant hogweed

One of the benefits of living in Cornwall is that you're never far from a public footpath - but while hedgerows full of spring wildflowers can look picturesque, not everything lurking in them is as pretty as it seems.

Hiding in plain sight is a plant that is often overlooked but can cause red blisters and sore skin even if the sap is simply brushed against.

For while giant hogweed bears a striking resemblance to its harmless relative common hogweed, as well as the often confused cow parsley, it is in fact a much nastier proposition and should be given a wide berth.

Here's how to tell the difference:

Cow parsley

Characterised by umbrella-like clusters of white, frothy flowers, cow parsley is a familiar sight along roadsides, hedgerows and woodland edges and can grow up to one metre tall.

The Wildlife Trusts describes the plant on its website as: "A hollow-stemmed, tall plant that grows rapidly in the summer before dying back.

"It likes shady habitats in particular, and can be found decorating woodland edges, roadside verges and hedgerows with masses of frothy, white flowers.

"These flower umbels (umbrella-like clusters) appear from May until June."

Cow parsley has large, flat umbrellas of small, white flowers, and large, fern-like leaves.

When crushed between the fingers, the leaves produce a strong, aniseed-like scent.

One of several common members of the carrot family, this is the most abundant, and the earliest-flowering of the plants known as umbellifers.

Common hogweed

Photo: Acabashi/Wikimedia Commons

Commons Common hogweed is a native plant (unlike giant hogweed) which can be found in abundance in hedgerows and on verges at this time of year in particular.

The Wildlife Trusts describes it as a member of the carrot family, displaying large, umbrella-like clusters of creamy-white flowers between May and August that are attractive to insects, although it can flower all year round.

The charity said: "Hogweed displays large, white umbels of flowers, and has hollow, hairy stems.

"Its leaves are broad, hairy and divided. It is not as tall as giant hogweed."

Giant hogweed

Photo: Natubico/Wikimedia Commons

As its name suggests, giant hogweed it a large plant with distinctively ridged, hollow stems that can grow to up to five metres.

Introduced by the Victorians as an ornamental plant for lakesides and gardens, it is an invasive weed of riverbanks, where it prevents native species from growing.

It is most common to find it between June and August, although people have already reported seeing it in Cornwall this year due to a particularly warm spring.

It likes damp conditions, especially in hedgerows near rivers and springs.

The Wildlife Trusts said: "It escaped into the wider countryside and gained notoriety in the 1970s as an alien species that favours damp spots like riverbanks.

"At this time, many children started to display blisters as a result of touching the plant's sap while using the stems to make pea-shooters or telescopes; sunlight makes the skin sensitive to the irritants in the plant, causing the skin to redden.

"Today, it is widely acknowledged that neither gardeners nor conservationists should attempt to cut the plant down (exposing its sap) as its toxins can cause serious, recurring skin damage."

The charity describes it as: "An immensely tall umbellifer (member of the carrot family) that displays large, white, umbrella-like clusters of flowers.

"Its hollow stem is ridged and purple-spotted, and its leaves are large and divided."