First, consider whether this can be done using non-chemical means such as digging out. Where these methods are not feasible, chemical controls may need to be used.
The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
Docks are difficult for gardeners to control by cultural methods once established.
Try digging isolated specimens out as only the top few inches of rootstock have powers of regeneration and if 12-15cm (5-6in) can be removed, usually there is no regrowth. Docks are especially vulnerable in spring so digging out at this time should be more effective.
Selective weedkillers in lawns:
- Dock seedlings can be killed by spraying with lawn weedkillers based on 2,4-D or MCPA (Vitax LawnClear 2 or Weedol Lawn Weedkiller), but they become fairly resistant to these weedkillers once they have established a fleshy rootstock
- Lawn weedkillers based on mecoprop-P may check the growth of docks but not completely kill them
- Apply lawn weedkillers in late summer after cutting off the flowering heads to prevent seeding, then re-spray leaves that re-grow 14 days after cutting back
Selective weedkillers in rough grassland:
- Use 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. wildflowers) and so should only be used in grass where such action is acceptable
- Glyphosate is a more effective treatment for established docks
- Apply when growing strongly from mid-summer onwards
- Glyphosate is not selective and any spray coming into contact with grass around the docks would be killed or severely checked
- Ready-to-use sprays or a gel formulation (Roundup Gel) can make application to individual weeds more accurate
- 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. Roundup Ultra, SBM Job done Tough Weedkiller (soluble sachet only), Resolva Pro Xtra Tough or Ecofective Rootblast Super Strength 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
- Sprays are most effective if applied from early June to mid-August
- As this weed is so persistent several applications may be necessary
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, b and 4)
Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale
Weeds: non-chemical control