Ground-elder

Perennial, spreading mainly by creeping underground stems, sometimes by seed. Although they have been found down to 30 feet or more in cave systems, the roots usually form a network just below the surface, so they are quite easily dug up. However every last trace must be removed because any small fragments will regenerate. This is why this weed is very difficult to eliminate as it is usually growing among other plants. It is premature to declare victory in the battle with Ground-elder without allowing a few years to pass. Vigilance is required for at least this amount of time for some re-emergance, particularily if it has been allowed to grow unchallanged for some time. The roots will have been widespread and it will have cast some seed which may germinate as new plants.
It is a member of the Umbellifer family so can act as an alternate host for the Carrot Fly Grub.
It was introduced to Britain from Continental Europe, possibly by the Romans, as a pot-herb and a medicine against rheumatism and gout (hence the common name). The leaves are made up of several leaflets, each on a short stalk and the main the leaf stalks are triangular in section. They can be boiled like spinach (as they still are in Scandinavia), or fresh young ones can be added to a salad - too much has a laxative effect. The dried root can be ground into a flour for baking.
In early summer upright stems can reach up to 100 cm and these carry the small white flowers which are are borne in umbels with 15 to 20 spokes.
A variegated variant is sold as an ornamental plant to be used as ground cover, but it should only be used where it can be isolated as it can become invasive, especially when it reverts to the natural green form.
Dig out as much of the white to buff-coloured cylindrical roots as possible using a fork. This will probably have to be repeated many times. It does not survive frequent mowing, so grassing over an infested area for a few years might work, but usually it resides in hedgerows which retain a reservoir of roots to reinfest the garden, so it is difficult to eradicate by cultivation. Be careful when accepting plants from another garden, as they can come with stowaways - if they have come from an area known to have Ground-elder tease out the roots to see if others are present and remove anything not attached to the plants. Affected plants can also be uprooted in the late autumn or early spring when they are dormant to remove infesting roots. Plunge the plant in a bucket of water to remove the soil and reveal the unwanted roots, then replant immediately so that they do not dry out. If the area is badly infested the plants could be replanted somewhere else temporarily, so that the weeds can be dealt with.
If it is coming from adjoining property a physical barrier burried to about 30 cm should deter it. After digging treat any regrowth with a systemic herbicide or if very patient, weekly visits to remove any plants which emerge. However this may take a long time and even after no regrowth for some months, a new plant can suddenly appear - possibly from seed. Any regrowth must be removed or treated immediately to exhaust the roots and prevent new ones from developing.
Never add the uprooted material to the compost heap, unless it has been allowed to dry out completely. Better to put in the recycling bin.
Companion planting with the annual Tagetes minuta (Muster-John-Henry) is said to inhibit growth so a barrier planting may slow the progress of the Ground-elder - this may just be the shading effect of the Tagetes as it can grow to 2 metres. Weedkillers to use:-
Glyphosate, systemic action, taken down into underground parts, spray or paint on depending on the situation. Use when the plants are growing well and are moving their sap at a higher rate. The greater the area of leaf that can be treated the better and resist the temptation to remove any topgrowth for at least two weeks after application - do remove flower spikes.
Dichlobenil applied in early spring, kills emerging shoots for up to a year among established woody plants or at the base of a mature hedge.

Nicholas Culpepper
(17th century astrologer-physician)
"Upon experiment it is found to heal the gout and sciatica. It is also used for aching joints and other cold pains."