The Control of Docks

The following notes derive from our own field scale studies, demonstrations & contracts. While we offer advice, we are also aware of the almost infinite variability of sites, weather, and management conditions.

Some examples of tasks, which can be suitable for handwork gangs

Docks (or Scotch thistle) in new seeds that are due to be conserved.
Docks (or any thistle) in cereal /vegetable crops (and around the edge)
Docks or any thistles (esp. Creeping & Scotch) in permanent pastures, banksides, fence-lines.
Ragwort anywhere, but especially on pasture (either protected by status or not).
Bracken in pasture, or spreading into heather (the latter very tricky),
Nettle clumps invading pastures.

DOCKS (Rumex sp) Some preventative measures

What encourages them to grow and spread?
Any section of a dock root is capable of producing buds and roots, especially when exposed to a good measure of light and moisture. The upper 6″ of roots may grow more vigorously, but all sections are potential plants. Dock seeds require particularly strong light to spark, in contrast to budding root sections, which search it out (especially in cultivated soil).

Preventative measures

Uproot them from pastures, leys, fence-lines. If a lower section of root is left in the ground, heal in the hole and keep going. In old pasture these remaining root tips often give up. Do this work before ploughing. Otherwise, plough early, and drag any root clusters to the surface with mounted chisel harrows, and take them off the field. [We sometimes use a reciprocating power harrow with sideways rather than rotary action, which helps to shake roots onto the surface ].Go for crop cover and the quick establishment of autumn sown grass & cereal crops. Don’t drill cereal seed too deeply. [Incidentally, we always use a break crop (forage) when coming out of grass, which gives us another chance to remove dock roots. It also avoids getting leather jackets in the cereal crop]. After potatoes, make sure any dock roots are picked out of the aulms left behind by the harvester.Always be vigilant about removing docks whenever they appear close to fields.

The feeding of contaminated silage or hay to ruminants is bad news. Many dock seeds survive their passage through animals, and get a head-start, by being coated in manure and then randomly deposited on open land.

Preventative measure

1) If you have a batch of contaminated feed, make sure it is only fed in yards or buildings. After mucking out, organize a hot compost for the bedding, which must cook the seeds for a minimum of 3 days at 55 C. Whole piles of dock roots can be treated in this way, and will have an ash-coated appearance if they have been cooked sufficiently.

3) Ruminants let into the aftermath of a hay/silage field, where docks have been left to mature in the fenceline, will nibble the seed heads from choice (and probably do get something useful from them). This can cause the spread of docks to the centre of a field. Even if the seed heads are immature when the animals first go in, they will mature later on, and get eaten. Over wintering, tight grazing and paddled land, will add to the problem.

Preventative measure

Flame-gun the trash under fence-lines, to help locate plants & kill off the surface seeds. Then pull the docks, or if time is short, top or cut off the maturing seed-heads early enough. Autumn/Winter strip-grazing is an ideal time to remove dock roots when they appear in strips, as the fence is moved forward. Grub out the small quantity of easily located roots, daily.

After using ring feeders / hay racks etc, the soil is exposed, allowing the surface seed bank access to light. Seedling docks will be among them. (Incidentally, we think that dock seeds are viable earlier than is generally supposed, and that plastic wrapping may even encourage their maturity ).

Preventative measure

Either feed on a special concreted area, or repair exposed & paddled soil by sowing quick-growing clovers & grass, after harrowing. Try and do this soon after the fodder racks are removed, and the earth has been exposed. If seedling docks do appear later, hook them out using the ships foot nose on the L-Dog.

Strong winds and birds can move dock seeds, and they can appear (unexpected), in lawns, new seeds and pasture.:

Preventative measure

Grub them out a.s.a.p., using the ‘sheeps foot nose. Regular mowing of lawns can persuade seedlings to give up, but in patures and leys, at least three low cuts (before the seed heads mature), would be necessary. Following this with close grazing of sheep during the growing season (only), might contain the problem.

Current L-D research includes: a) looking at the viability of dock seeds at different stages of growth / in wrapped & chopped silage / haylage. b) the long-term effect of chiselling creeping thistle and c) grubbing out ragwort at the rosette stage.
Removing docks with a Lazy Dog ‘A stitch in time saves nine‘

Docks are rarely easy, for a variety of reasons. As 1st year plants, (or plants kept small by regular sheep nibbling), they can be awkward to locate, and fiddly to lift. Docks in old grasses vary in size, so that old and massive root systems (very satisfactory to lift) grow alongside modest 1st or 2nd year plants. In old grassland, there always seem to be more plants than one predicts, and the different characteristics of clay soils, sandy soils, stony conditions, can make it difficult to choose which grubbing nose to use on the tools. Experience provides the best guide to when to change to a fork, and this is helped by another general skill that develops: the accuracy with which an operator can locate the crown of a plant in long grass. Yet another skill, is judging the best distance back from each crown, for inserting the grubbing nose. We often have two tools at hand. One with NO1b (sheeps’ foot), and the other with NO8 (large fork).
Some pulling tips 

1) Pull docks in moist conditions, especially on heavy land which can turn into concrete by the end of May. Young docks growing in sandy soils can get easier to lift, when a small amount of surface compaction or dryness holds the soil together. Always place the grubbing nose (of your choice), well back from the plant. When removing large docks there is no guarantee that the tool will engage the actual root, so support each lift with a wedge of soil (especially in cultivated or sandy conditions).

2) Pull docks in the Autumn/Winter, while strip grazing lambs, and remove the plants in each band of freshly that is freshly eaten. On bigger grassland tasks, we often mark out the field with vehicle wheel markings. This gives each member of the gang a limited area to concentrate on, and ensures coverage of the field. Throw the up-rooted plants into piles for collection later. Always wear thick soled boots & gloves.

3) Develop regular use of the 2nd (lower)handle, when lifting the uprooted plant to waist height for removing it from the fork. Remember to employ the same hand on the 2nd handle, after it has been used to pull back & extract the root (using the top handle), and get out of the garden fork habit of bending to the ground, (which doesn’t come immediately to regular users of a garden fork !). Some bending is inevitable but keep it minimal… and sometimes it’s easiest to swing the tool completely upside down, in order to pull the root cluster from the fork.

The Control of Scotch/Spear Thistle (Cirsium vulgare)

This biannual can infest new seeds, pastures, crop margins and fencelines. Some fields retain a large seed-bank, and surprising proportions of land can be covered by the plant after reseeding. We once calculated that nearly a third of a 6.5 acre pasture was covered in rosettes. After a determined effort with our tools, the same field took one man just two hours to clear of rosettes in following years. Many of these new rosettes sprung from the seed-bank, following winter sheep-grazing.

Anyone who has topped their pastures, will know that Scotch thistle responds to cutting by coppicing and then growing an increased number of seed heads, which are too low for mechanical cutting. Our approach is to uproot this plant at the two leafed or small rosette stage, during autumn, winter & early spring, when the land is moist. The nose for doing this job is the ‘sheep’s foot’ (NO1b). We don’t leave them until late in the Spring, when the ground has hardened and the roots have become long or engaged in subsoil.

The crowns of maturing rosettes divide into several roots during the 2nd year (or end of the first), and each root can produce a viable seed-head, if it is left exposed in the ground. So we try and get them young. There’s no need to remove the uprooted plants from the field or crop (as with docks & ragwort), so just leave them on the surface to wither & die.

Method

The first year of grubbing out a badly infested pasture or ley, can seem like an impossible task, and it is not really a job for one person (unless he is known to be fond of his own company). Always try to work in gangs (minimum two), and organize some kind of methodical line. We often use the tyre marks of vehicles to make parallel lines, so that the whole field is walked methodically. It’s sensible not do too much on the first day, because the technique doesn’t come immediately. Two good hours might well be enough. The ultimate aim is to uproot each and every potential flowering rosette from the ground, and after the first batch of uprooted thistles have withered away, follow up is necessary, to deal with missed plants. If the team keeps going and completes this first year attack, huge improvements will be seen in the following season. We recently cleared 12 acres of 8452 rosettes in 2.25 man-days (using inexperienced labour and five separate visits to the field).

Preventative measures

1) Less tight grazing and paddling of land, leads to less thistles.

2) After the first clearance of a field, a conservation crop allows the land to repair and shade any lurking seed-bank. Hay crops are an old ploy to discourage thistles.

3) It will always worth be checking over the field, after it has been grazed. A ten minute visit to stock can be combined with a little weeding, if the tools are at hand [The Lazy Dog & ‘sheeps-foot’ nose, the Chisel Hoe, the Weedhook.].

4) Thistles are not able to grow in tree-shaded areas of fields, but do grow in hedge bottoms, where the light creeps in. We remove these awkward plants late in the 2nd year, by cutting them off at ground level with a weedhook, and bonfiring them.

5) Do everything to keep on good terms with your neighbours, because Scotch thistle seed blows a long way. Best to offer help and spend an hour with a weedhook in the fence-line.

CREEPING THISTLE (Cirsium arvense) & THE NEW CHISEL HOES

‘Chisel out two, and get a weaker one back’

This rhisome-connected thistle can be attacked within 2/3 weeks of the first appearance of rosettes in early April. By May rosettes are about 6″ high (in North Yorkshire), and we chisel them just below the ground, where the stem is still white. If they are cut higher up, in the green part of the stem, vigorous tillering occurs at ground level (as happens after normal mowing or topping). Chiseling them just below ground level, forces the plant to re-shoot from another point along its’ rhisome. This regrowth will appear quite quickly, but it is a weakened form of the plant, less prickly, shorter and unable to achieve seed head maturity (except sometimes in really wet growing areas). Research tells us that the vigour of this plant is almost totally dependant on moisture, and that fertility levels are relatively unimportant.

What are the immediate advantages of chiseling creeping thistle?

1) Pastures are cleared earlier, allowing access to a greater eating area for animals.

2) Animals do not prickle their noses in their search for clean grazing. This helps to eliminate orf in sheep.

3) The softer, less prickly re-growth, rarely reaches sufficient maturity to seed.

4) After chiseling, the induced re-growth weakens the plant rhisome from year to year, and on banksides (or any place where moisture is low), the annual improvement is dramatic.

5) On flat, well drained pasture, the cumulative effect of repeated chiseling, not only leads to clearer grazing, but weakens the plant annually.

The plant does not like being chiseled at any stage of its’ development right up to the appearance of seed heads, and there is no doubt that thistle beds that have had this treatment, will show the greatest improvements in the following season. If possible, repeated chiseling in the first season is worth doing, especially in the wet areas.

Mowing or Topping: this form of control can be effective long term, but only when it is carried out when the majority of thistle rods are approaching budding. Don’t do this it too late (and cause the seeds to mature on the ground), or too early ( and cause ground level tillering). Later cutting causes greater weakening of the rhisome.

Our all-steel chisel hoe has been developed over many seasons. It was
designed to be as light as possible and to enter the ground easily, using its’ own weight. This does not happen with shock absorbing wooden shafted tools. We use both hands and a rotary motion of the arms, and in dense thistle beds, achieve a strike rate of 35 rosettes a minute. We regularly sharpen the hoe blade with carborundum.

The Control of Creeping Thistle (Cirsium arvense)

The species has fewer spines on the margins of the first leaves than the other thistles.

One of the worst weeds, it occurs abundantly in grassland, arable and waste land throughout the British Isles spreads by far-creeping roots which can really regenerate new plants from small pieces, and to a lesser extent by seed

Spear Thistle (Cirsium vulgare)

Spear thistle is a common biennial of the grassland and waste places throughout the British IslesThe most distinctive feature of this thistle is the second true leaf which can be very large and is a dull dark green with dense vertical whitish hairs on the upper surface.

Marsh Thistle (Cirsium palustre)

A biennial weed of wet pastures, common throughout the British Isles.
This thistle differs from the other species in having longer spines on the margins of the first true leaves and broader, less tapered leaf bases.

Thistle

There are three types of thistle common in Ireland:

(1) Creeping Thistle (Cirsium arvense)

(2) The Spear Thistle (Cirsium vulgare)

(3) The Marsh Thistle (Cirsium palustre)

The Creeping Thistle

The creeping thistle is one of our most troublesome noxious weeds. It thrives equally well in reasonably fertile grassland and in tillage ground, but it is usually absent on soils of low fertility. Winter poaching and overgrazing in Spring encourages the spread of thistles. In grassland its prickly nature prevents animals grazing close to the base of plants. Stock forced to graze on heavily infested pastures may suffer skin eruptions about the mouth.

The creeping thistle is a perennial plant, the overground parts of which die down at the end of each growing season. It produces large numbers of seeds which have a very low vitality and only a small percentage are capable of germinating. In any event seed is not necessary for propagation, because the underground portions which resemble roots produce shoots which can give rise to thistle plants. When these are allowed to grow unchecked, they in turn produce their own roots which spread out underground, so that an ever-increasing area of land is infested each year. This spread of roots is extremely rapid, a small portion of a root being known to produce 18 m (60 feet) of root system in two years.

Control

Cutting

The root system of creeping thistle is, in fact, a reserve of food to enable the plant to survive the winter and produce plants the following Spring. The object of cutting is to exhaust the food reserves in the roots. If cutting is postponed until the plants have reached the flowering stage, the roots will have accumulated the additional reserves of food, and cutting then serves little useful purpose.

To eradicate the creeping thistle cutting must be systematic. Cut when the plants are 10-15 em (4-6 inches) high, usually early in June. At that stage the food reserves in the roots are at a very low ebb. Further efforts by the roots to produce fresh shoots will further deplete the food reserves. The fresh shoots should also be cut down and even a third cutting may be necessary. Cutting as outlined should eradicate the creeping thistle in about three years. There is no evidence whatever to support the belief that if cutting is delayed until autumn, rain will penetrate the hollow stem of the plant and cause the roots to decay.

Spraying

On tillage and young leas, where soil disturbance has led to an abundance of young thistles, MCPA salt used at 1.4 kg per hectare, MCPB salt or 2-4D13-amine used at 2.25 kg per hectare, or 2-4-D amine used at 0.70 kg per hectare are all effective. On established pastures effective chemical control is more difficult. MCPA or 2-4-D amine used at 1.4 to 1.68 kg per hectare will give good control of top growth, but respraying is usually necessary. Both MCPA and 2-4-D amine retard clover growth, but MCPB and 2-4-DB do not suppress clovers. Best results are generally obtained if spraying is carried out in the early flower bud stage when the weeds are growing vigorously.

Spear and Marsh Thistles

Both these thistles are biennial plants. They are spread by means of fertile seeds which germinate in late summer or autumn and produce plants in rosette form close to the ground. In the following season the centre of the rosette grows up into one or more branched stems reaching heights of up to 1 m (3 feet). Both plants carry pale purple flowers and when seeds have been produced the plants die off. Seeds are scattered over wide areas by means of wind drift.

Control

Since these plants depend entirely on their seed for regeneration, control is much easier than in the case of creeping thistle. Prevention of seeding is of crucial importance. This can be achieved by spudding out rosettes at a depth of about 5 em (2 inches) below ground-level or when spudding cannot be done, by cutting the stems while the flower heads are in the unopened bud stage. Cutting in consecutive years or spot treatment with a hormone type spray may also be used to control these thistles.

MAFF advice on control of injurious weeds specified in the Weeds Act 1959

Injurious weeds can be controlled using a number of chemical and cultural means. Care should be taken to choose the most appropriate method for each site circumstance. This applies particularly to sites of special conservation interest where control of the injurious weeds may risk damaging rare or valuable flora and fauna. In these situations expert advice should be sought before any action is taken.

Injurious Weed Control using Herbicides

N.B. This document is kept under review to check the continuing validity of the herbicide recommendations, and revisions are issued as necessary.

The application of herbicides is subject to regulations which must be observed when using products. These are summarised in theCode of Practice for the Safe Use of Pesticides on Farms and Holdings (available from MAFF Publications, quoting reference PB3528).

Instructions for use including operator and environmental protection, the crops or plants on which the product may be used, maximum dose, harvest interval and other details are shown on the product label. Each time a product is used you must READ THE LABEL AND FOLLOW THE INSTRUCTIONS. Some products are only available to operators who hold a certificate of competence as recognised by the Ministry of Agriculture, Fisheries and Food.

Non Selective Herbicide Treatment

Control of injurious weeds can be undertaken using a non-specific herbicide such as glyphosate either as an overall spray or using a height selective applicator or spot treatment.

Selective Herbicide Treatment

Injurious weeds can be controlled using selective herbicides. Although most products are generally used as an overall spray, some can also be applied through a selective height applicator or as a spot treatment to improve their selectivity.

The following shows the most favoured active ingredients for the control of each injurious weed specified under the Weeds Act 1959. These active ingredients may be available alone or in mixtures with other chemicals and qualified advice should be obtained to determine the most appropriate product especially when mixed populations of weeds occur.

N.B. Herbicides (marked *) are referred to by active ingredient not product name

• SPEAR THISTLE (Cirsium vulgare)

Spear thistle occurs widely on lowland and upland grassland and waste places. The weed competes effectively with crops for water, light and nutrients. It is biennial and only spreads by seed. Mature plants are normally 30-50 cm tall, with flowers from July through to late autumn. Large numbers of seeds are produced which can be blown by wind across farm and field boundaries.

CONTROL The plants can be cut each year before mid-July to prevent shedding of viable seed. It is also possible to remove them by digging. Long-term control is possible from herbicide treatment; spear thistle is susceptible to clopyralid* and moderately susceptible to MCPA* herbicides. Where clover is an important constituent of the sward, a mixture of MCPA* and MCPB* herbicides is more appropriate.

• CREEPING OR FIELD THISTLE (Cirsium arvense)

Creeping thistle can quickly dominate vegetation in grassland or waste ground. The weed forms dense patches which suppress crop plants.

Mature plants extend 30-100cm in height, with flowers from July into late autumn each year. The plants produce only a few viable seeds which can be blown by wind. However, invasion is more often by spread of the plants’ underground root systems.

CONTROL Cultivation is not an effective means of control as the number of root pieces which can throw up new shoots is increased. Control on arable land therefore is usually by use of a range of herbicides depending on the field crop grown.

On grassland, cutting at flower stem extension but before opening of the flower buds will prevent seed spread for a particular season. Repeated cutting at the same growth stage over several years may “wear down” an infestation.

MCPA* herbicide applied during the early bud stage will kill the aerial parts of the plant, but repeat treatments the following year may be necessary for complete control. One application of the herbicide clopyralid* is normally sufficient to achieve an acceptable level of control.

• BROAD-LEAVED DOCK (Rumex obtusifolius) AND CURLED DOCK (Rumex crispus)

Broad-leaved dock thrives in high nitrogen environments, open swards and where there is heavy treading by stock. Curled dock occurs more commonly on arable and waste land.

Both species produce many seeds which can remain viable in soil for decades. Buds on pieces of tap-root broken by soil disturbance or treading will produce new plants. The two species are similar in appearance but leaf shape differs, as reflected in their names. Hybrids are common between the species and this can hinder identification. Flowering for both species is from late June until early autumn with inflorescences reaching over 100 cm in height.

CONTROL

Broad-leaved Dock

Curled Dock

• COMMON RAGWORT (Senecio jacobaea)

This is the only ragwort species specified in the Weeds Act 1959; other species of Senecio are not so widespread as common ragwort. Flowering is from late June onwards to early autumn when the characteristic yellow inflorescences usually extend between 30-100 cms in height.

The weed occurs in neglected grass fields, on uncropped ground and sand dunes. It prefers light soils of low fertility, particularly in over or under- grazed pasture. Common ragwort is biennial when undisturbed but can develop perennial characteristics following cutting or treading.

POISONOUS TO LIVESTOCK Cattle and horses are particularly susceptible to poisoning by common ragwort but sheep are also susceptible. Palatability of the weed increases when plants are conserved in hay or silage or treated with herbicide. An added problem is that livestock cannot easily reject fragments of ragwort in conserved herbage and its poisonous alkaloids are unaffected by the conservation process.

CONTROL Although short-term action can be undertaken to clear existing plants, reinfestation will be rapid unless overall husbandry is improved, particularly for uncropped ground and grassland.

Cutting: Cutting and stem removal at the early flowering stage reduces seed production but does not destroy the plant. Cut plants left lying in the field are a serious risk to grazing animals and may still set seed. These should be removed and burned within theCode of Practice for the Protection of Air (available from MAFF Publications, quoting reference PB0618).

Pulling (and digging): Pulling or digging can also prevent seed spread but may not give long-term control. Plants should be removed and burned within the Code of Practice for the Protection of Air (see above).

Herbicides: No single herbicide treatment will completely eliminate a ragwort infestation due to successive germinations of the weed. Treatment with selective herbicides can be made to the plant rosettes usually late spring and in the autumn before frost damages the foliage. The most effective material for overall spraying is 2,4-D* but this will damage clover and a number of other plant species.

WHICHEVER METHOD OF CONTROL IS SELECTED, REMEMBER NOT TO TURN GRAZING ANIMALS INTO THE FIELD UNTIL ANY TREATED RAGWORT PLANTS HAVE DIED AND DISINTEGRATED. DO NOT ALLOW RAGWORT TO BE HARVESTED IN HAY OR SILAGE FOR LIVESTOCK FEED.

Revised May 2000

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The Control of Bracken

Bracken is now a menace, because over the last century it has hugely increased its coverage of heather and pasture, and because it continues its increase exponentially. A hundred years ago, many villagers were pig owners or small scale stockmen, who cut bracken for animal bedding, and for whom access to choice bracken beds was competetive. The areas nearest to the villages may well have been cut twice (annually), and it is thought that this cutting once kept it under control. Other reasons for its most recent spreading could be the ability of the plant to fix nitrogen from a polluted atmosphere, or its use of higher fertility levels (from larger sheep flocks).
All manner of mechanical means have been tried to tame it during the last 50 years, and yet there still remain areas of disagreement. Some scientists advocate crushing the fronds in late July, others advocate 2 cuts each year, while still others, suggest only one late cut. The truth is that large, long-term experiments with machinery are rare, and that most land-owners use the chemical Asulox to control it. This practice seems likely to continue, despite the expense, and despite the lack of research into many aspects of chemicals short/long term effects (see report of E.P.A.). Of course, bracken itself contains noxious chemicals, and releases carcinogenic spores in August, which means that destroying it by hand or mechanical means, is not always a safe option, and that masks are worth wearing.

On our sheep-stray area of moorland, bracken has been contained by the use of Azulox (in the past). Our current non-chemical strategy mainly involves blade-strimming in late June/July, and repeated hand chiselling in isolated beds. Deep chisel hoeing and hoiking, is much more damaging than cutting (and decreases the shoot numbers), but it needs determined labour & lots of time. Chiselling in long heather can be awkward, so we sometimes resort to pulling the young ferns by hand.

Generally speaking, mechanical mowing or crushing is slow and difficult, and in some awkward areas of terrain, even small-scale crushers are limited to where they can go. The effect of this mechanical work is mostly to contain the problem. If it is relentless, then less foliage is produced, and spreading can be controlled. If the foliage of any rhisome plants is damaged often enough, energy levels are weakened, so that repeated attacks in the same season must be more damaging than a single one, in late July. With bracken, this is an opinion that is well supported by other peoples research.