The Great or Giant Water Dock (Rumex Hydrolapathum) is the largest of all the Docks. Dock is a generalist name applied to a widespread group of rhubarb-like, broad-leaved perennial herbaceous wayside plants.


It can grow up to 5-6’ high, with several erect, furrowed stems, initially green turning reddish brown, arising from its thick, blackish root, each stem is branched in the upper part, and bear numerous green flowers in almost leafless whorls, turning red-brown from July-September.


The leaves can grow very large, up to 1-3’ long; they’re dull green, not shiny, lance-shaped and narrow, tapering at both ends. The lower leaves towards the base tend to be fuller and more heart-shaped.


Docks can contain quite high levels of oxalic acid, which gives the leaves a bitter acid-lemon flavour. Perfectly alright if eaten in small quantities, but problematic if eaten in large amounts since the oxalic acid can lock-up other nutrients in the food, especially calcium, precipitating possible mineral deficiencies.

Rumex hydrolapathum

The Great water Dock had medicinal properties, E. R. Rohde in The Old English Herbals published in 2010 says:

‘It is interesting to find that Turner identifies the Herba Britannica of Dioscorides and Pliny (famed for having cured the soldiers of Julius Caesar of scurvy in the Rhine country) with Polygonum bistorta, which he observed plentifully in Friesland, the scene of Pliny’s observations. This herb is held by modern authorities to be Rumex aquaticus (Great Water Dock).’


It was also used as a stomach tonic, recipe: 2 oz. of the root sliced placed into 3 pints of water, with a little cinnamon or liquorice powder, and boiled down to a quart and a wineglassful taken two or three times a day.


It’s further claimed in a number of herbals that the astringent qualities of the root render it good in addressing diarrhoea, the seeds (as with the other Docks) having been used for the same purpose. Whilst the green leaves are reputed to be an effective application for ulcers of the eyes.

Culpepper said of the Docks:

‘The seed of most kinds, whether garden or field, doth stay laxes and fluxes of all sorts, and is helpful for those that spit blood. The roots boiled in vinegar helpeth the itch, scabs and breaking out of the skin, if it be bathed therewith. The distilled water of the herb and roots have the same virtue and cleanseth the skin from freckles…. All Docks being boiled with meat make it boil the sooner…’

Further reading:


More Canal Flora plant portraits HERE.


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