Great Water Dock
Rumex hydrolapathum
Family: Polygonaceae
What it is like
Rumex hydrolapathum is a PERENNIAL growing to 1.8 m (6ft). See above for USDA hardiness. It is hardy to UK zone 6 and is not frost tender. It is in flower from July to September, and the seeds ripen from August to September. The species is hermaphrodite (has both male and female organs) and is pollinated by Wind. It is noted for attracting wildlife. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil and can grow in water.
Height (m): 1.8
Where it is found
Near ponds and streams, also in shallow water, avoiding acid conditions.
Western Europe, including Britain, from Scandanavia south and east to Spain, Italy and S. Russia.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 1
Young leaves - cooked. Seed - raw or cooked. It can be ground into a powder and used as a flour. The seed is small and rather fiddly to harvest.
Seed: includes nuts, cereals, peas and beans.
Medicine
Rating: 1
The root is antiscorbutic and strongly astringent. It is harvested in early spring and dried for later use. The green leaves are said to be an excellent application for ulcers of the eyes.
Antiscorbutic: A plant rich in vitamin C that is used to counteract scurvy.
Astringent: Produces contraction in living tissue, reducing the flow of secretions and discharges of blood, mucus, diarrhoea etc.
Ophthalmic: Treats eye complaints.
Other
Rating:
The roots contain tannin. In cultivated plants, those grown on dry land contained 6 - 8% tannin whilst those grown in water contained 12.4 - 21.6%. The dried and powdered root makes a good tooth cleaner. Dark green to brown and dark grey dyes can be obtained from the roots of many species in this genus, They do not need a mordant.
Dye: Plants that provide dyes.
Tannin: An astringent substance obtaied from plants, it is used medicinally, as a dye and mordant, stabilizer in pesticide etc.
Teeth: Plants used to clean and care for the teeth.
Attracts Wildlife: Plants noted for attracting wildlife
How it is grown
Requires a moist or wet soil, also succeeding in shallow water. Avoids acid conditions in the wild. A very important food plant for the caterpillars of many species of butterfly.
Propagating it: Seed - sow spring in situ. Division in spring.
Best place to grow: Pond; Bog Garden;
Habit: Perennial
Hardiness: 5-9
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: Semi-shade, no shade
Moisture: Moist, wet, water
Things to keep in mind
Plants can contain quite high levels of oxalic acid, which is what gives the leaves of many members of this genus an acid-lemon flavour. Perfectly alright in small quantities, the leaves should not be eaten in large amounts since the oxalic acid can lock-up other nutrients in the food, especially calcium, thus causing mineral deficiencies. The oxalic acid content will be reduced if the plant is cooked. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition.