Where Petasites is growing amongst plants, e.g. herbaceous perennials, carefully lift valuable plants and free them of the weed before replanting.
Winter heliotrope (Petasites fragrans) cannot stand efficient cultivation so thorough and repeated digging, rotovating or deep hoeing will eliminate it. Improving drainage will also reduce the weed’s vigour.
Where cultivation is not possible consider covering the affected areas with a weed membrane or thick, light-excluding bark mulch for at least 6 months.
Repeated strimming or mowing will eliminate the weed from empty ground.
Vigilance is needed to remove any seedlings as they appear.
- Apply glyphosate as a spot treatment to individual plants or spray areas that have been cleared of cultivated plants
- Glyphosate is a non-selective weedkiller applied to the foliage, where it is translocated throughout the weed. Tougher formulations are worth trying (e.g. Scotts Roundup Ultra, Bayer Garden Rootkill Weedkiller, Bayer Garden Super Strength Weedkiller or Doff Maxi Strength Glyphosate Weedkiller)
- Being non-selective it is essential to avoid spray drift onto neighbouring plants. It is important to have good leaf coverage so that as much chemical is absorbed as possible
- Protect cultivated plants with sheet polythene or by pegging them out of the way, and take care to avoid spray drift. The gel formulation (Scotts Roundup Gel) may be easier to apply in such a situation
- Sprays are most effective if applied mid-summer or later when the plants are growing strongly. There may be re-growth the following spring necessitating further treatment
In rough grassland:
Apply a selective weedkiller which contains triclopyr (SBK Brushwood Killer) as this would leave the grass unharmed. This herbicide is systemic, travelling from the weed foliage down into the root system
However as it is non-selective any broad-leaved plants will be damaged (e.g. wild flowers) and so should only be used in grass where such action is acceptable.
Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 1a and 4)
Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale
Weeds: non-chemical control