Perennial weeds persist over the winter normally as tap roots, root tubers or underground stems known as rhizomes. This page describes the problem and suggests some organic methods for control.

COUCH GRASS, TWITCH - Elymus repens (Agropyron repens)

has tough yellowish wiry rhizomes. Where it has invaded new land the rhizomes may form a matt just under the surface. Slipping a garden fork carefully under this can lift it all up together fairly easily. Take care not to leave any behind.

On land that has been cultivated the rhizomes may go deeper. Removal by hand is then very laborious. A mulch covering such as cardboard or polythene maintained over say 2 growing seasons should reduce the problem considerably. Rotovation is possible on soil types where it won’t be damaging. But it should be done in dry conditions and needs to be repeated over 2 – 3 months whenever regrowth appears. One-time rotovation only worsens the problem by chopping weeds into many pieces. If allowed, couch grass will grow intimately with cultivated plants making them unsightly and weeding difficult. These plants will need to be lifted and the soil sprayed off the root system with water in order to reveal the couch grass rhizomes and remove them all.

BINDWEED - Calystegium sepium

is a climber with spear shaped leaves and white trumpet-like flowers. Underground it produces fleshy white rhizomes. These are very brittle, break easily and re-grow from small pieces. Weed out before planting perennials or shrubs, especially before planting hedges. Bindweed is commonly found along old hedgerows and seems to like walls too.

Bindweed can persist for a long time in the soil. Once I weeded a bed and buried all the bindweed roots deeply together in one hole. As it happened they produced little growth but when, after some years, I revisited the hole I found the Bindweed roots as fresh as the day they were buried. Bindweed doesn’t like disturbance, so keep digging it up and don’t let is see the light of day.

HORSETAIL - Equisetum sp.

consists of erect or horizontal fine stems but no leaves. It may also produce a cone which releases spores. The aerial stems come from underground stems that easily penetrate surfaces such as tarmac and gravel. The plant also propagates from bulbils. This is not a nice weed especially among flowers, but it can be beaten.

The absence of leaves is the plant’s weakness. It relies on the small stem surface area to gather sunlight. Therefore competition with plants that cast deep shade will set it back. With a potato crop for example, the gardener can remove the horsetail during cultivating and harvesting and the potato plants provide strong competition in between. Ridding it from the flower garden may require a temporary change of plan.

GROUND ELDER - Aegopodium podagraria

buds are at ground level and can grow into a dense leaf cover held 6”–18” above ground. The leaf cover casts deep shade and soil becomes dry. The flowers, if left, are white umbels but germinating seedlings are virtually insignificant.

Ground Elder spreads by underground stems (rhizomes).

The picture shows white stems growing horizontally and grey stems growing straight down before buds appear. The roots are fine fibrous and grow out from nodes on these stems.

The weed is often found near old tips used to dump weeds. It can easily find its way under a fence.

If you tackle this by forking it out be sure to remove all the underground parts. It can be reduced by continual cutting and by a sheet mulch, and see Tagetes minuta.

Tagetes minuta

has been noted for combating, Ground Elder, Bindweed, and Couch Grass. It probably works by producing growth inhibitory root exudates. In the UK it is a half hardy annual. T. minuta grows 4-8’ high and is also known as Stinkweed, Wild Marigold or Marigold. But in California T. minuta is itself listed as a noxious weed. Problems may be avoided by cutting down flowers well before seed dispersal.

LESSER CELANDINE – Ranunculus ficaria

has a rosette of kidney shaped leaves and pretty yellow buttercup flowers with some petals paling to white. I stupidly introduced this into my garden from a local woodland. It formed a neat clump increasing in size. But the real trouble began when I decided to weed some of it out. When grown as a wild flower, confine to the shade and don't disturb it. It emerges early and its dense cover will smother later wild flower seedlings.

Lesser Celandine can reproduce from root tubers and bulbils. The root tubers break apart easily on weeding. The bulbils are fleshy buds in the leaf axils capable of growing new plants. You should never add Lesser Calandine or connected soil to the compost heap. If digging up include the plant within a soil ball and treat all this as contaminated. But the plant dies after submerging in water for some time.

The plant completes its lifecycle by early summer when it dies down. So if you specialize in shrubs, fruit or planting out summer bedding you may wish to tolerate it for the pretty yellow spring flowers. But when cultivated it spreads.

Never weed the plant after flowering in early summer, it’s a waste of time. The root tubers will have developed and be ready to break apart and spread. The leaves yellow quickly beneath a polythene or cardboard mulch. But the plant is capable of producing long leaf stalks through several inches of loose organic matter. I’m currently experimenting with using a flame weeder on Lesser Celandine and have hopes that it will succeed if done early enough. Watch this space.

DANDELION - Taraxicum sp.

roughly translated means lion’s tooth and refers to lance shaped leaves with large toothed margins. The leaves form into a rosette surmounting a tap root. Some gardeners use Dandelion leaves as a herb.

The plant produces yellow composite flower heads that develop into feathery balls of seeds. Dispersal by wind should be stopped.

The tap root goes straight down deep, but may branch if previously cut by weeding. Attempts to remove it often leave some root behind. The picture shows how regrowth occurs from old root.

When the soil is soft, use a garden spade and fork to dig as deep as possible. Carefully loosen soil around plant root with fork before lifting. The Weed & Planting Knife is probably the best small tool for effective removal. Use in lawns to cut straight down deep around the root. Also try a Dandelion Weeding Tool - a notched blade on a long metal rod. I don't find weed gripping tools of any use (they may work better in sandy soils).

Dandelions that grow in mown lawns have leaves are appressed to the ground that avoid being cut. This habit smothers the grass. But in long grass the leaves grow erect, being wider and with few or no teeth.

Dandelion is more difficult when growing next to paths or between pavings. After cutting leaves, try placing a pile of stones over the plant. If it grows through the stones cut it off at ground level and replace the stones.

CREEPING, COMMON OR CROW FOOT BUTTERCUP - Ranunculus repens

the common buttercup has a 3 lobe stalked leaf arising in a rosette. Animals eating the leaves suffer a reaction from poisons it contains.

It spreads by seeds and, similar to strawberry plants, by surface stems called stolons that root at the nodes. But its fibrous roots don’t persist and it is easy to clean out using a daisy grubber or ordinary claw grubber.

DOCKS - Rumex sp.

have large rather leathery oblong leaves on an erect stem. They also have a deep tap root. They can be lifted with the garden spade but take care not to put them directly on the compost heap - instead wash soil off and place in a plastic bag with other perennial weeds. Removing the top 6” of root will prevent re-growth.

NETTLES - Urtica sp.

have heart shaped leaves with a serrated margin and are covered with stiff stinging hairs. The flowers are small of an inconspicuous pale green. The stringy roots are bright yellow but look out for cream / purple underground stems that extend the plant. These are just beneath the surface.

A nettle patch is valuable for wildlife.

To save being stung avoid brushing against them and either wear gloves or grasp the nettle firmly.

The plant is pretty easy to remove using a garden fork. First knock down the top to about 1 feet with a sharp sickle or hedge clippers. This prevents tall stems brushing onto you as you dig.

Nettles also drop hundreds of seeds around the plant. Remove top growth to compost heap before flowers turn to seed. Don’t compost flower or seed heads directly.

Nettles are rich in nutrients and health enhancing chemicals. They make a good compost accelerator. You can even make liquid nettle feed in the same way as liquid comfrey feed.

THISTLES - Asteraceae

have spiny leaves, some forming a tight rosette in the first year and in the second year extending an erect stem with flowers. The stem is a sturdy tap root which can be dug out with the aid of a garden spade and gloves.

Thistles are susceptible to root aphids and these also infect lettuce which, belong to the same plant family. Eradication is also important to prevent seed dispersal.

Further information on weeds

BOOKS ON ORGANIC WEED CONTROL

For more information try these books.

Controlling Weeds Without Chemicals Jo Readman

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