How common is Japanese knotweed in Co. Cork?

The National Biodiversity Data Centre and other recorders have logged 1,490 knotweed records in Co. Cork (1,603 including giant hogweed), the latest in 2025. Records cluster along rivers, railway lines and roadsides, and reflect where people record as much as where the plant grows.

Will a bank lend on a house with knotweed?

Irish lenders have no blanket rule, but valuers now note it, and where it is within seven metres of the house they may ask for a management plan or knock the valuation. UK lenders decline outright. Ask the seller in writing whether it is or was on the property and for treatment records.

What does it cost to deal with?

Herbicide treatment runs three to five seasons at a few hundred euro a year for a small stand. Excavation and licensed disposal for a large stand runs into five figures. Never cut it and put it in the green bin: a fragment regrows.

Japanese knotweed · Co. Cork

Japanese knotweed in Co. Cork: 1,490 public records

Public biodiversity records hold 1,490 Japanese knotweed sightings for Co. Cork, the latest from 2025. A record near the house is a mortgage question, not a gardening one.

1,490

Japanese knotweed records in Co. Cork (GBIF / NBDC)

113

giant hogweed records

2025

most recent record year

Knotweed in Co. Cork

Japanese knotweed spreads along rivers and railways and from dumped garden waste. It goes three metres down and seven metres out, comes up through tarmac and drains, and a piece the size of a fingernail regrows. In Co. Cork, public biodiversity records (via GBIF, mainly the National Biodiversity Data Centre) hold 1,490 knotweed sightings. Counts depend on who was recording: a county with an active recorder scores high.

Records within 2 km of town centres, for the towns we hold detail on:

Cork City	149 records
Cork	144 records
Blackrock	87 records
Bishopstown	85 records
Douglas	67 records
Bandon	43 records
Rochestown	33 records
Ballincollig	28 records
Kinsale	28 records
Glanmire	21 records
Skibbereen	21 records
Clonakilty	17 records

For a house, what matters is a record within about 250 m, and the lane or stream behind the garden. Walk the boundary at a viewing; the stems are hollow, bamboo-like, with red speckles, and the leaves are shield-shaped.

Check one house in Co. Cork

The area tells you the odds. The report tells you about the house.

Enter the Eircode. The free snapshot shows which of the twenty-nine checks flag up. The full report (€24.99, one house, no account) lists knotweed and giant hogweed records within 250 m of the house with year and distance, and tells you what to ask the seller in writing.

Or read the sample report first: a real house, 16 pages.

Other checks for Co. Cork

Questions people ask

How common is Japanese knotweed in Co. Cork?: The National Biodiversity Data Centre and other recorders have logged 1,490 knotweed records in Co. Cork (1,603 including giant hogweed), the latest in 2025. Records cluster along rivers, railway lines and roadsides, and reflect where people record as much as where the plant grows.
Will a bank lend on a house with knotweed?: Irish lenders have no blanket rule, but valuers now note it, and where it is within seven metres of the house they may ask for a management plan or knock the valuation. UK lenders decline outright. Ask the seller in writing whether it is or was on the property and for treatment records.
What does it cost to deal with?: Herbicide treatment runs three to five seasons at a few hundred euro a year for a small stand. Excavation and licensed disposal for a large stand runs into five figures. Never cut it and put it in the green bin: a fragment regrows.

Sources

Area figures, compiled from public records. They describe the town or county, not any one house. The paid report checks the exact Eircode.

Japanese knotweed in Co. Cork: 1,490 public records

Knotweed in Co. Cork

The area tells you the odds. The report tells you about the house.

Other checks for Co. Cork

Other counties

Questions people ask