Giant Hogweed Seedling Emergence

The Scottish Invasive Species Initiative has been running a sheep grazing trial since 2019 to investigate how land managers can use grazing pressure as a control method for substantial giant hogweed infestations. As part of the trial we will be producing a guidance document detailing best practice for land managers.

There are two key factors to implementing a successful grazing regime. First is the correct grazing pressure - created both by the number of sheep and the length of time the sheep are on the site. This is being investigated through our sheep grazing trials near Macduff, at the bottom of the Deveron catchment in Aberdeenshire.

The second factor is the time of year sheep are deployed on site as it is important to ensure they are grazing at the peak times for seedling emergence. However, little is known about the emergence time of giant hogweed seedlings in Scotland - and this is where our trial comes in!

1m² plot in the seedling emergence trial, May 2021, in the River Lossie catchment in Moray

The Trial

When do giant hogweed seedlings emerge in simulated grazing conditions?

The trial ran across 10 river catchments across north-east Scotland from March - October 2022, with project and partner staff and volunteers taking part. Participants visited their 1m² plot monthly to count the number of giant hogweed seedlings and remove them to simulate grazing. So what were the results? Follow the link below to find out.

Seedling emergence study

Thank you to everyone who participated in the study! Results from this trial will directly inform seasonal management plants for giant hogweed control, including our Macduff sheep grazing trial.

Giant hogweed seedlings of various size and morphology