Crack willow

Salix × fragilis · Salicaceae · also Brittle willow

A broad, fast-growing willow to 25 m whose brittle twigs snap with an audible crack and root wherever they wash up, so a single tree can colonise a whole river. In Britain it is a familiar pollarded riverside tree. In New Zealand and Australia it chokes waterways, diverts flow, drops leaves that deoxygenate streams and displaces native riparian trees: it is banned from sale, propagation and distribution under the NZ National Pest Plant Accord 2020 and is a Weed of National Significance declared in every Australian state.

Broadleaf, loses its leaves in winterFast growingFull sunNeeds steady water

Where it stands

Native

This tree evolved here, and local wildlife depends on it.

  • 🇹🇷 Türkiye · WCVP records the hybrid as native to Türkiyesource

Adapted

Introduced, but it handles this climate and has not shown a habit of spreading.

  • 🇩🇪 Germany · Introduced per WCVPsource
  • 🇬🇧 United Kingdom · Long naturalised and planted along rivers; introduced per WCVPsource

Prohibited

Selling or planting it is banned here.

  • 🇦🇺 NSW, Australia · Willows (except weeping, pussy and sterile pussy willow) are a Weed of National Significance declared in all states and territoriessource
  • 🇦🇺 SA, Australia · Weed of National Significance; declaredsource
  • 🇦🇺 TAS, Australia · Weed of National Significance; declaredsource
  • 🇦🇺 VIC, Australia · Weed of National Significance; declaredsource
  • 🇳🇿 New Zealand · Listed in the 2020 National Pest Plant Accord: an unwanted organism banned from sale, propagation and distribution; also on DOC's 2024 list of environmental weedssource

Care

Do not plant in New Zealand or Australia; in its naturalised European range pollard every 5 to 15 years in winter to keep it safe. Control is by cut-and-paint or stem injection of herbicide, leaving dead trees standing a year before removal so banks do not collapse; broken twigs re-root, so bag and remove them. Replace with local native riparian species.

Benefits

Holds soilFlood tolerantFast canopyPollinators

Good for

Streambanks

Watch out for

Invasive elsewhereWeak woodLarge roots