Weed control is the botanical component of
pest controlPest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy....
, stopping weeds from reaching a mature stage of growth when they could be harmful to domesticated
plantPlants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants,...
s and
livestockLivestock are one or more domesticated animals raised in an agricultural setting to produce commodities such as food or fiber, or labor...
by physical and chemical methods. In order to reduce weed growth, many "weed control" strategies have been developed in order to contain the growth and spread of weeds.
The most basic is ploughing which cuts the roots of annual weeds. Today, chemical weed killers known as
herbicideA herbicide is a substance used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant hormones...
s are widely used.
The effects of weeds on other plants
Weeds can compete with productive crops or pasture, or convert productive land into unusable scrub. Weed are also often poisonous, distasteful, produce burrs, thorns or other damaging body parts or otherwise interfere with the use and management of desirable plants by contaminating harvests or excluding livestock.
Weeds tend to thrive at the expense of the more refined edible or ornamental crops. They provide competition for space,
nutrientA nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. Nutrients are the substances that enrich the body. They build and repair tissues, give heat and energy, and regulate body processes...
s, water and light, although how seriously they will affect a crop depends on a number of factors. Some crops have greater resistance than others- smaller, slower growing seedlings are more likely to be overwhelmed than those that are larger and more vigorous.
OnionOnion is a term used for many plants in the genus Allium. They are known by the common name "onion" but, used without qualifiers, it usually refers to Allium cepa. Allium cepa is also known as the "garden onion" or "bulb" onion...
s are one of the crops most susceptible to competition, for they are slow to germinate and produce slender, upright stems. Quick growing, broad leafed weeds therefore have a distinct advantage, and if not removed, the crop is likely to be lost. Broad beans however produce large seedlings, and will suffer far less profound effects of weed competition other than during periods of water shortage at the crucial time when the pods are filling out. Transplanted crops raised in sterile seed or potting
compostCompost is a combination of food material and other organic material that is being decomposed through aerobic decomposition into a rich black soil. The process of composting is simple and practiced by individuals in their homes, farmers on their land, and industrially by cities.Compost soil is...
will have a head start over germinating weed seeds.
Weeds also differ in their competitive abilities, and can vary according to conditions and the time of year. Tall growing vigorous weeds such as
fat henFat hen or fat-hen is a common name for various plants with succulent or juicy leaves, often species that are used as a vegetable:* Aristolochia rotunda * Atriplex prostrata...
(
Chenopodium album) can have the most pronounced effects on adjacent crops, although seedlings of fat hen that appear in late summer will only produce small plants.
ChickweedChickweed, a common name, can refer to:* Cerastium - Mouse-ear Chickweed* Holosteum - Jagged Chickweed* Moenchia - Upright Chickweed* Paronychia - Chickweed* Stellaria pro parte - Chickweed...
(
Stellaria media), a low growing plant, can happily co-exist with a tall crop during the summer, but plants that have overwintered will grow rapidly in early spring and may swamp crops such as onions or spring greens.
The presence of weeds does not necessarily mean that they are competing with a crop, especially during the early stages of growth when each plant can find the resources it requires without interfering with the others. However, as the seedlings’ size increases, their root systems will spread as they each
begin to require greater amounts of water and nutrients. Estimates suggest that weed and crop can co-exist harmoniously for around three weeks, therefore it is important that weeds are removed early on in order to prevent competition occurring. Weed competition can have quite dramatic effects on crop growth. Harold A Roberts cites research carried out with onions wherein "Weeds were carefully removed from separate plots at different times during the growth of the crop and the plots were then kept clean. It was found that after competition had started, the final yield of bulbs was being reduced at a rate equivalent to almost 4% per day. So that by delaying weeding for another fortnight, the yield was cut to less than half that produced on ground kept clean all the time." (
The Complete Know And Grow Vegetables, Bleasdale, Salter and others, OUP 1991). He goes on to record that
"by early June, the weight of weeds per unit area was twenty times that of the crop, and the weeds had already taken from the soil about half of the nitrogen and a third of the potash which had been applied".
PerennialA perennial plant or perennial is a plant that lives for more than two years. When used by gardeners or horticulturalists, this term applies specifically to perennial herbaceous plants...
weeds with bulbils, such as
lesser celandineLesser celandine, is a low-growing, hairless perennial plant, with fleshy dark green, heart-shaped leaves. The plant is found throughout Europe and west Asia and is now introduced in North America...
and
oxalisOxalis is by far the largest genus in the wood-sorrel family Oxalidaceae: of the approximately 900 known species in the Oxalidaceae, 800 belong here...
, or with persistent underground stems such as couch grass (
Agropyron repens) or
creeping buttercupRanunculus repens is a flowering plant in the buttercup family, native to Europe, Asia and northwestern Africa....
(
Ranunculus repens) are able to store reserves of food, and are thus able to grow faster and with more vigour than their annual counterparts. There is also evidence that the roots of some perennials such as couch grass exude allelopathic chemicals which inhibit the growth of other nearby plants.
Weeds can also host pests and diseases that can spread to cultivated crops. Charlock and Shepherd’s purse may carry
clubrootClubroot is a common disease of cabbages, radishes, turnips and other plants belonging to the family Cruciferae . It is caused by Plasmodiophora brassicae, which was once considered a slime mold but is now put in the group Phytomyxea. It has as many as nine races. Gall formation or distortion takes...
, eelworm can be harboured by chickweed, fat hen and shepherd’s purse, while the
cucumber mosaic virusCucumber mosaic virus is a plant pathogenic virus in the family Bromoviridae .It is the type member of the plant virus genus, Cucumovirus . This virus has a worldwide distribution and a very wide host range . In fact it has the reputation of having the widest host range of any known plant virus...
, which can devastate the
cucurbit familyCucurbitaceae is a plant family commonly known as melons, gourds or cucurbits and includes crops like cucumbers, squashes , luffas, melons and watermelons...
, is carried by a range of different weeds including chickweed and groundsel.
However, at times the role of weeds in this respect can be over-rated. As far as
insectInsects are arthropods, having a hard exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae. They are the most diverse group of animals on the planet and include more than a million species that are already described. Insects represent more than half of all...
pests are concerned, often the species that live on weeds are not the same as those that attack vegetable crops;
"Tests with the common cruciferous weeds such as shepherds purse have shown that they do not act as hosts for the larvae of the cabbage root flyDelia radicum, known variously as the cabbage fly, cabbage root fly, root fly or turnip fly, is a pest of crops. The larvae of the cabbage root fly are sometimes known as the cabbage maggot or root maggot...
. One exception was found to be the wild radish, but this is not usually a weed of established vegetable gardens" (Roberts,
The Complete Know And Grow Vegetables). However pests such as
cutwormThe term cutworm is used for the larvae of many species of moth. Most cutworms are in the moth family Noctuidae, however, many noctuid larvae are not cutworms. Cutworms are notorious agricultural and garden pests. They are voracious leaf, bud, and stem feeders and can destroy entire plants...
s may first attack weeds then move on to cultivated crops.
While charlock, a common weed in southeastern
USAThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, may be considered a weed by row crop growers, it is highly valued by beekeepers, who seek out places where it blooms all winter, thus providing pollen for honeybees and other pollinators. Its bloom is resistant to all but a very hard freeze, and even that will only kill it back briefly. By feeding an array of pollinators during a seasonal dearth, it can redound to the farmer's advantage. Many weeds are likewise highly beneficial to pollinators.
Methods
In domestic gardens, methods of weed control include covering an area of ground with several layers of wet newspaper or one black plastic sheet for several weeks. In the case of using wet newspaper, the multiple layers prevent light from reaching all plants beneath, which kills them. Saturating the newspaper with water daily speeds the decomposition of the dead plants. Any weed seeds that start to sprout because of the water will also be deprived of sunlight, be killed, and decompose. After several weeks, all germinating weed seeds present in the ground should be dead. Then the newspaper can be removed and the ground can be planted. The decomposed plants will help fertilise the plants or seeds planted later.
In the case of using the black plastic sheet, the
greenhouse effectThe greenhouse effect is the heating of the surface of a planet or moon due to the presence of an atmosphere containing gases that absorb and emit infrared radiation. Thus, greenhouse gases trap heat within the surface-troposphere system...
is used to kill the plants beneath the sheet. A 5-10 cm layer of wood chip
mulchIn agriculture and gardening, is a protective cover placed over the soil, primarily to modify the effects of the local climate. A wide variety of natural and synthetic materials are used.- Purposes :...
on the ground will also prevent most weeds from sprouting. Also, gravel can be spread over the ground as an inorganic mulch. In agriculture, irrigation is sometimes used as a weed control measure such as in the case of paddy fields. Many people find that although the black plastic sheeting is extremely effective at preventing the weeds in areas where it covers, in actual use it is difficult to achieve full coverage.
Knowing how weeds reproduce, spread and survive adverse conditions can help in developing effective control and management strategies. Weeds have a range of techniques that enable them to thrive;
AnnualAn annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
and
biennialA biennial plant is a flowering plant that takes two years to complete its biological lifecycle. In the first year the plant grows leaves, stems, and roots , then it enters a period of dormancy over the colder months. Usually the stem remains very short and the leaves are low to the ground, forming...
weeds such as
chickweedChickweed, a common name, can refer to:* Cerastium - Mouse-ear Chickweed* Holosteum - Jagged Chickweed* Moenchia - Upright Chickweed* Paronychia - Chickweed* Stellaria pro parte - Chickweed...
, annual meadow grass, shepherd’s purse, groundsel,
fat henFat hen or fat-hen is a common name for various plants with succulent or juicy leaves, often species that are used as a vegetable:* Aristolochia rotunda * Atriplex prostrata...
,
cleaverThe word cleaver has a number of uses:*Cleaver is a large form of knife.*Cleaver , in descriptive geology, is a ridge of rock that separates a unified flow of glacial ice from its uphill side into two glaciers flanking, and flowing parallel to, the ridge.*Cleaver is a burr-bearing plant *Cleaver ...
,
speedwell-Places named Speedwell:* Speedwell, Bristol, in England* Speedwell Island, one of the Falkland Islands* Speedwell, Tennessee, an unincorporated town in Tennessee-Other:* Speedwell Cavern...
and hairy bittercress
propagatePlant propagation is the process of artificially or naturally distributing plants.-Sexual propagation :Seeds and spores can be used for reproduction . Seeds are typically produced from sexual reproduction within a species, since because genetic recombination has occurred plants grown from seed may...
themselves by seeding. Many produce huge numbers of seed several times a season, some all year round. Groundsel can produce 1000 seed, and can continue right through a mild winter, whilst Scentless Mayweed produces over 30,000 seeds per plant. Not all of these will germinate at once, but over several seasons, lying dormant in the soil sometimes for years until exposed to light.
PoppyA poppy is any of a number of colorful flowers, typically withone per stem, belonging to the poppy family. They include a number of attractive wildflower species with colorful flowers found growing singularly or in large groups; many species are also grown in gardens...
seed can survive 80-100 years, dock 50 or more. There can be many thousands of seeds in a square foot or square metre of ground, thus and soil disturbance will produce a flush of fresh weed seedlings.
See also
Bradley Method of Bush RegenerationThe Bradley Method of Bush Regeneration is a method of weed control in natural areas of bushland, developed by sisters Joan and Eileen Bradley, in Sydney, Australia in the mid 1960s.The Bradley method makes practical use of well known ecological principles...
, which uses ecological processes to do much of the work.
"Stale seed bed" technique
One technique employed by growers is the ‘
stale seed bedA false or stale seed bed is a useful organic weed control technique which involves creating a seedbed some weeks before seed is due to be sown...
’, which involves cultivating the soil, then leaving it for a week or so.
When the initial flush of weeds has germinated, the grower will lightly
hoeA Hoe is an agricultural tool used to*agitate the surface of the soil around plants, to remove weeds*pile soil around the base of plants ;*create narrow furrows and shallow trenches for planting seeds and bulbs;...
off before the desired crop is planted. However, even a freshly cleared bed will be susceptible to airborne seed from elsewhere, as well as seed brought in by passing animals which can carry them on their fur, or from freshly imported
manureManure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen that is trapped by bacteria in the soil...
. The organic solution to the problem of spreading annual weeds lies in regular, properly timed weeding, preferably just before flowering (fortuitously, this is also the time at which they will be of the most value in
compostingComposting is the purposeful biodegradation of organic matter, such as yard and food waste. The decomposition is performed by micro-organisms, mostly bacteria, but also yeasts and fungi...
).
This technique is also quite often used by farmers who let weeds germinate then return the soil before crop sowing.
PerennialA perennial plant or perennial is a plant that lives for more than two years. When used by gardeners or horticulturalists, this term applies specifically to perennial herbaceous plants...
weeds also propagate by seeding; the airborne seed of the dandelion and the rose-bay willow herb are parachuted far and wide. But they also have an additional range of vegetative means of spreading that gives them their pernicious reputation. Dandelion and dock put down deep tap roots, which, although they do not spread underground, are able to regrow from any remaining piece left in the ground. Removal of the complete tap root is the only sure remedy.
The most persistent of the perennials are those that spread by underground creeping
rhizomeIn botany, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
s that can regrow from the tiniest fragment. These include couch grass,
bindweedBindweed may refer to:* Convolvulus, a genus of about 250 species of flowering plants* Calystegia , a related genus of about 25 species of flowering plants* Black bindweed, a fast-growing annual flowering plant...
, ground elder,
nettleNettle is the common name for between 30-45 species of flowering plants of the genus Urtica in the family Urticaceae, with a cosmopolitan though mainly temperate distribution...
s, rosebay willow herb,
Japanese knotweedJapanese Knotweed is a large, herbaceous perennial plant, native to eastern Asia in Japan, China and Korea...
,
horsetailEquisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. They are commonly known as horsetails....
and
brackenBrackens are a genus comprising several species of large, coarse ferns. Ferns are vascular plants that have alternating generations, large plants that produce spores and small plants that produce sex cells . Brackens are in the family Dennstaedtiaceae, which are noted for their large, highly...
, as well as creeping thistle, whose tap roots can put out lateral roots. Other perennials put out runners that spread along the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
surface. As they
creep along they set down roots, enabling them to colonise bare ground with great rapidity. These include creeping buttercup and ground ivy. Yet another group of perennials propagate by
stolonIn biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.-In botany:...
s- stems that arch back into the ground to reroot. Most familiar of these is the
brambleBrambles are thorny plants of the genus Rubus, in the rose family . Bramble fruit is the fruit of any such plant, including the blackberry and raspberry. The word comes from Germanic *bram-bezi, whence also German Brombeere and French framboise...
.
All of the above weeds can be very difficult to eradicate- thick black
plastic mulchPlastic mulch is a product used, in a similar fashion to mulch, to suppress weeds and conserve water in crop production and landscaping. Certain plastic mulches also act as a barrier to keep methyl bromide, both a powerful fumigant and ozone depleter, in the soil. Crops grow through slits or...
es can be effective to a degree, although will probably need to be left in place for at least two seasons. In addition, hoeing off weed leaves and stems as soon as they appear can eventually weaken and kill the plants, although this will require persistence in the case of plants such as bindweed. Nettle infestations can be tackled by cutting back at least three times a year, repeated over a three year period. Bramble can be dealt with in a similar way. Some plants are said to produce root exudates that suppress
herbA herb is a plant that is valued for flavor, scent, or other qualities. Herbs are used in cooking, as medicines, and for spiritual purposes....
aceous weeds.
Tagetes minuata is claimed to be effective against couch and ground elder, whilst a border of
comfreyFor the place, see Comfrey, MinnesotaComfrey is an important herb in organic gardening, having many medicinal and fertilizer uses.- Description :...
is also said to act as a barrier against the invasion of some weeds including couch.
Use of herbicides
The above described methods of weed control avoid using chemicals. They are often used by farmers. However, these methods may damage a fragile soil by restructuring it, hence are not always used. They are those preferred by the organic gardener or
organic farmerOrganic farming is the form of agriculture that relies on crop rotation, green manure, compost, biological pest control, and mechanical cultivation etc.....
.
However weed control can also be achieved by the use of herbicides. Selective herbicides kill certain targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often based on plant
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
s. Herbicides are generally classified as follows;
- Contact herbicides destroy only that plant tissue in contact with the chemical spray. Generally, these are the fastest acting herbicides. They are ineffective on perennial plants that are able to re-grow from roots or tubers.
- Systemic herbicides are foliar-applied and are translocated through the plant and destroy a greater amount of the plant tissue. Modern herbicides such as glyphosate
Glyphosate is a broad-spectrum systemic herbicide used to kill weeds, especially perennials. It is typically sprayed and absorbed through the leaves, injected into the trunk, or applied to the stump of a tree, or broadcast or used in the cut-stump treatment as a forestry herbicide...
are designed to leave no harmful residue in the soil.
- Soil-borne herbicides are applied to the soil and are taken up by the roots of the target plant.
- Pre-emergent herbicides are applied to the soil and prevent germination or early growth of weed seeds.
In
agricultureAgriculture is the production of food and goods through farming and forestry. Agriculture was the key development that led to the rise of human civilization, with the husbandry of domesticated animals and plants creating food surpluses that enabled the development of more densely populated and...
large scale and systematic weeding is usually required, often by machines, such as
liquidLiquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material. The surface is a free surface where the liquid is not constrained by a container....
herbicideA herbicide is a substance used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant hormones...
sprayerA sprayer is a device used to spray a liquid.In agriculture, a sprayer is a piece of equipment that applies herbicides, pesticides, and fertilizers to agricultural crops...
s, or even by
helicopterA helicopter is an aircraft that is lifted and propelled by one or more horizontal rotors, each rotor consisting of two or more rotor blades. Helicopters are classified as rotorcraft or rotary-wing aircraft to distinguish them from fixed-wing aircraft because the helicopter achieves lift with the...
(such as in the USA), to eliminate the massive amount of weeds present on farming lands.
However there are a number of techniques that the
organic farmerOrganic farming is the form of agriculture that relies on crop rotation, green manure, compost, biological pest control, and mechanical cultivation etc.....
can employ such as
mulchIn agriculture and gardening, is a protective cover placed over the soil, primarily to modify the effects of the local climate. A wide variety of natural and synthetic materials are used.- Purposes :...
ing and carefully timed cutting of weeds before they are able to set seed.
(See also section below on UK legislation regarding the control of certain weeds)
Organic methods
Typically a combination of methods are used in organic situations.
- Drip irrigation
Drip irrigation, also known as trickle irrigation or microirrigation, is an irrigation method which saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and...
: Rubber hoses and other methods are used to bring water directly to the roots of the desired plants. This limits weed access to water.
- Manually pulling weeds: Labourers are used to pull weeds at various points in the growing process.
- Mechanically tilling around plants: Tractors are used to carefully till weeds around the crop plants at various points in the growing process. Besides tilling, other mechanical weed control methods also exist
- Ploughing: Ploughing includes tilling of soil, intercultural ploughing and summer ploughing. Ploughing through tilling of soil uproots the weeds which causes them to die. In summer ploughing is done during deep summers. Summer ploughing also helps in killing pests.
- Crop rotation: Rotating crops with ones that kill weeds by choking them out, such as hemp
Hemp is the name of the soft, durable fiber that is cultivated from plants of the Cannabis genus, cultivated only for industrial use....
, Mucuna pruriensMucuna pruriens is a tropical legume known by a multitude of common names .-Common names:* Velvet bean* Cowitch* Cowhage* Juckbohne * Picapica* Kapikachu* Yerepe * Atmagupta...
, and other crops, can be a very effective method of weed control. It is a way to avoid the use of herbicides, and to gain the benefits of crop rotation.
- Weed mat: A weed mat is an artificial mulch
In agriculture and gardening, is a protective cover placed over the soil, primarily to modify the effects of the local climate. A wide variety of natural and synthetic materials are used.- Purposes :...
, fibrous cloth material, bark or newspaper laid on top of the soil preventing weeds from growing to the surface.
Wood
Besides those kinds of weeds which are of an herbaceous nature, there are others which are woody, and grow to a very considerable size; such as
broomBrooms are a group of evergreen, semi-evergreen, and deciduous shrubs in the subfamily Faboideae of the legume family Fabaceae, mainly in the three genera Chamaecytisus, Cytisus and Genista, but also in five other small genera . All genera in this group are from the tribe Genisteae...
,
furzeGorse, furze, furse or whin is a genus of about 20 species of spiny evergreen shrubs in the subfamily Faboideae of the pea family Fabaceae, native to western Europe and northwest Africa, with the majority of species in Iberia.Gorse is closely related to the brooms, and like them, has green stems...
and
LantanaLantana is a genus of about 150 species of perennial flowering plants, native to tropical regions of the Americas, Africa and existing as an imported plant in numerous areas, especially in the Australian-Pacific region. The genus includes both herbaceous plants and shrubs growing to tall...
s. The first may be destroyed by frequent ploughing and harrowing, in the same manner as other perennial weeds are. Another method of destroying broom is by pasturing the field where it grows with grazers.
The best method of extirpating furze is to set fire to it in frosty weather, for frost has the effect of withering and making them burn readily. The stumps must then be cut over with a hatchet, and when the ground is well softened by rain it may be ploughed up, and the roots taken out by a harrow adapted to that purpose. If the field is soon laid down to
grassPasture is land with low-growing vegetation cover used for grazing of livestock as part of a farm, or in ranching or other unenclosed pastoral systems. Prior to the advent of factory farming, pasture was the primary source of food for grazing animals such as cattle and horses...
, they will again spring up; in this case, pasturing with grazers is an effectual remedy. The thorn, or bramble, can only be extirpated by ploughing up the ground and collecting the roots.
In June, weeds are in their most succulent state, and in this condition, after they have lain a few hours to wither, cattle will eat almost every species. There is scarcely a hedge, border, or a nook, but what at that season is valuable.
UK legislation concerning weeds
The
Weeds Act, 1959 is described as
"Preventing the spread of harmful or injurious weeds", and is mainly relevant to
farmerA farmer is a person who raises living organisms for food or raw materials.- Definition :The term farmer usually applies to a person who grows field crops, and/or manages orchards or vineyards, or raises livestock or poultry such as chicken and cows...
s and other
ruralRural areas are large and isolated areas of a country, often with low population density.About 91 percent of the rural population now earn salaried incomes, often in urban areas...
settings rather than the
allotmentAllotment gardens are characterised by a concentration in one place of a few or up to several hundreds of land parcels that are assigned to individuals or families...
or
gardenA garden is a planned space, usually outdoors, set aside for the display, cultivation, and enjoyment of plants and other forms of nature. The garden can incorporate both natural and man-made materials. The most common form is known as a residential garden. Western gardens are almost universally...
scale grower.
There are five ‘injurious’ (that is, likely to be harmful to agricultural production) weeds covered by the provisions of the Weeds Act. These are:
- Spear thistle (Cirsium vulgare)
- Creeping or field thistle (Cirsium arvense)
- Curled Dock
Curled Dock , also known as Curly Dock, Yellow Dock, Sour Dock, Narrow Dock, sometimes as "narrow-leaved dock" , and ambiguously as "garden patience", is a perennial flowering plant in the family Polygonaceae, native to Europe and western Asia.The mature plant is a reddish brown colour, and...
(Rumex crispus)
- Broad leaved dock
Rumex obtusifolius, commonly known as Broad-leaved Dock, Bitter Dock, Bluntleaf Dock, Dock Leaf or "butter dock", is a perennial weed, native to Europe but can now be found in the United States and many other countries around the world.- Identification :Rumex obtusifolius is easily recognizable by...
(Rumex obtusifolius)
- Common ragwort (Senecio jacobaea) (nb, this weed is poisonous to livestock
Livestock are one or more domesticated animals raised in an agricultural setting to produce commodities such as food or fiber, or labor...
. Livestock should not be allowed to graze where ragwort has grown until it is eradicated, and any traces have disintegrated. Ragwort should not be allowed to be harvested in hay or silage for feed).
DEFRA provide guidance for the treatment removal of these weeds from infested land. Much of this is oriented towards the use of
herbicideA herbicide is a substance used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant hormones...
s, the majority of which may not be acceptable to the
organic producerOrganic farming is the form of agriculture that relies on crop rotation, green manure, compost, biological pest control, and mechanical cultivation etc.....
(apart from non-synthetic substances like
sulphurSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
, which in some circumstances are accepted within
Soil AssociationThe Soil Association is the UK's leading organic campaigning and certification body. A membership charity, it campaigns against intensive farming methods in favour of local, seasonal and organic food and farming. The association developed the world’s first organic certification system in 1967...
standards) but in most cases there are manual techniques that can be used such as digging out the roots,
mulchIn agriculture and gardening, is a protective cover placed over the soil, primarily to modify the effects of the local climate. A wide variety of natural and synthetic materials are used.- Purposes :...
ing out or carefully timed cutting before seeds are able to spread.
Primary responsibility for weeds control rests with the occupier of the land on which the weeds are growing, therefore it is important to be alert to potential weed problems and to take prompt action. However, it should be remembered that most common farmland weeds are not "injurious" within the meaning of the Weeds Act, and many such plant species have conservation and environmental value. When dealing with complaints under the Weeds Act, DEFRA has a duty in law to try and achieve a reasonable balance between different interests. These include agriculture, countryside
conservationConservation is an ethic of resource use, allocation, and protection. Its primary focus is upon maintaining the health of the natural world: its forests, fisheries, habitats, and biological diversity. Secondary focus is on materials conservation and energy conservation, which are seen as important...
and the public in general. Constructive discussion about problems caused by weeds can often result in effective solutions and avoid the need for DEFRA to take official action. In addition to those weeds covered by the 1959 act, under section 14 of the
Wildlife and Countryside Act 1981The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom which aims to protect the wildlife and countryside of the United Kingdom...
, it can be an offence to plant or grow certain specified plants in the wild (see Schedule 9 to the Wildlife and Countryside Act 1981), including
Giant HogweedGiant Hogweed is a plant in the family Apiaceae, native to the Caucasus Region and Central Asia. It may reach 2-5 metres tall...
and
Japanese KnotweedJapanese Knotweed is a large, herbaceous perennial plant, native to eastern Asia in Japan, China and Korea...
. Problems involving these plants can be referred to the local authority for the area where those weeds are growing as some local authorities have bye-laws controlling these plants. There is no statutory
requirement for landowners to remove these plants from their property.
External links