Much of the information in this section is based on Ranwell (1972a), Venner (1977), and Ellis (edit. 1983).

Sea buckthorn is a very thorny shrub, growing usually as a bush up to 3m (10′) tall, but occasionally found as a tree up to 6m (20′) tall.

Its spiny branches and narrow, linear leaves, greyish- green on the upper surfaces and silvery below, are unmistakable.

Sea buckthorn is dioecious, ie male and female flowers are borne on separate plants. This difference is easiest to see on older plants in winter, as the flower buds of male plants are large while those of females are small. The females bear pale yellow to bright orange berry-like fruits which tend to hang on the branches through the winter.

Sea buckthorn

Pollen records suggest that sea buckthorn was formerly widespread in Britain on nutrient-rich soils exposed at the end of the last glaciation, but with the spread of forests it was pushed to a few isolated dry sandy sites on the east coast of Britain between Kent and East Lothian. It may possibly be native to a few west coast sites as well. Starting in the mid-18th century it was introduced for erosion control purposes on many sites around the coasts of Great Britain and Ireland as well as inland. Although it has since died out in some places, it has continued to spread in others and has colonised new sites from-bird-sown seeds. Since the early 1950s sea buckthorn populations have exploded due to the virtual end of rabbit grazing, possibly aided by increasing soil nutrient levels due to fallout from air pollution.

Reasons for control

Sea buckthorn may be controlled in order to:

  1. Prevent it invading open and fixed sand dune communities, where it suppresses other lower-growing plants and leads to permanent changes in dune habitats
  2. Restrict or eliminate it on sites of scientific interest where it is not native but has been introduced deliberately or accidentally in the past, in order to maintain or restore more truly natural conditions.

FACTORS TO CONSIDER

  1. Sea buckthorn appears well suited to most semi-natural dune habitats other than permanently flooded hollows, dune heaths and the arctic-alpine conditions of the northernmost British dunes. Wherever it invades, it is liable to replace existing plant communities. Because of this, the Hippophae Study Group recommended that while it be allowed to develop to maturity in its most natural and interesting east coast sites, it should be managed to provide greater diversity of shrub species on most of its altered west coast sites and that it be eliminated from or prevented from establishing itself on most other sites. (See Ranwell, 1972a, pp46-9, for management recommendations for individual sites.)
  2. Sea buckthorn has a number of positive uses in addition to consolidating and protecting exposed sandy areas (see here for planting methods). It provides material for brushwood fencing, thatching and dead and live hedges. It can be planted as an aid to dune afforestation. It provides shelter for picnic sites and car parks and can also be used to reclaim waste land.
  3. Dense sea buckthorn stands have little value for most wildlife but they do provide nest sites for a variety of birds (especially warblers in young stands) and cover for foxes, rabbits and small mammals. They are important winter feeding areas for fieldfares and other thrushes. Where other scrub species are lacking, it is worth retaining some sea buckthorn habitat and cutting the stands in rotation to diversify their age structure.
  4. Sea buckthorn tolerates a variety of soils but it is most prolific on well-drained soils with adequate lime. On lime-poor soils it grows poorly and is prone to insect attack. Seedlings germinate only where the soil salinity is under 0.05%. Mature plants are more salt tolerant but they cannot penetrate the dune-salt marsh transition zone. Sea buckthorn is a nitrogen-fixing species which can colonise nitrogen-poor soils. The decaying roots of cut plants release the nitrogen in a form which can be used by nettles (Urtica dioica) and other nitrogen-demanding species, so the plant community which results from sea buckthorn clearance is unlikely to be the same as that which precedes it. The dense leaf litter can also have an adverse effect on the germination of duneland species.
  5. Sea buckthorn is light demanding and is killed soon after being overshadowed by taller trees or fast-growers such as elder (Sambucus nigra).
    Sea buckthorn seedlings cannot survive the shade of the parent plants and mature specimens tend to become bare underneath from overshadowing branches. In some places old (eg twenty years or more) stands seem to be dying of their own accord. It seems likely that other species, protected from winds and grazing animals by the sea buckthorn, may invade and diversify many unmanaged stands and lead eventually to the development of woodland conditions.
  6. It is possible to restrict the spread of newly introduced sea buckthorn by insuring that only individuals of one sex are planted. It is best to use all males, since if females are used there is some danger of fertilisation from self-seeded male plants or pollen blown into the area from outside. At Holkham NNR, Norfolk, it has been found that old female bushes occasionally develop fertile seed even when the flowers are carefully isolated from pollination. Sexes of young plants are hard to distinguish, so it is important to weed out any plants of the wrong sex as soon as you notice them.
  7. Even single-sex stands spread vigorously by suckering around the periphery, unless controlled. At Braunton Burrows. Devon, plants have been known to spread 2.1m (7′) in every direction in a single _year and at Yellowcraig, East Lothian, vegetative spread is estimated to be as much as 4.3m (5 yds) per year (East Lothian County Council, 1970, p22).
  8. Once plants of both sexes are present over a large area, the only answer to their continued spread is total eradication. In the long run this is less laborious and more effective than any attempt to restrict the spread and multiplication of colonies or to selectively cut female plants to stop seed production (Venner, 1977).
  9. Sea buckthorn clearance is a job for cold weather and experienced, well-equipped workers. Protective clothing is essential. Heavy-duty hedging gauntlets and a safety helmet with visor and ear protectors, or at least a hat and goggles, are especially important. Anyone felling or spraying should also wear a tough jacket such as a ‘Barbour’ jacket and heavy leather ‘chaps’ (trousers cannot turn the thorns). Wear the jacket over the saw harness, when using a scrub cutter, to stop branches catching in the straps. Wear leather boots, not wellies which are liable to puncture. Resist the temptation to strip off and hope for the best – you are likely to end up at hospital with a thorn in too deep for DIY removal.
    If you can’t afford full equipment for the entire work group, be sure at least that the power tool user is properly clad. Volunteers who are helping to clear up behind the power tool user should take great care and work slowly to reduce the risk from thorns.

Control methods

A variety of control methods may be used on sea buckthorn, depending on the age and density of plants, the size of the stand and problems of regrowth. On many sites a varied programme is most effective. For example, at Braunton Burrows, the yearly programme, now mainly completed, involved cutting in winter, burning felled material in spring, and spraying regrowth and stands of first year seedlings in late summer and autumn. Scattered first-year seedlings are sprayed or are pulled up by hand as the opportunity allows. However, the effectiveness of treatments varies greatly from one part of the country to another. On a few sites, such as Whitford NNR, Gower, regrowth is nil and a straightforward cutting programme has been enough to virtually eliminate the plant. By contrast, at Murlough NNR, Co. Down, neither cutting nor spraying have been found effective, and large areas have had to be grubbed up (see below).

Where you combine winter cutting with summer-autumn foliar spraying, be sure to fell only as big an area as you can later treat by spraying. Otherwise unsprayed regrowth may get out of hand and have to be cut a second time.

Cutting

Advantages:

  1. Cutting is selective and thorough.
  2. Cutting is the easiest way to get rid of large plants where a mower or bulldozer is unavailable or site access is difficult.

Disadvantages:

  1. Cutting is labour intensive and may be costly.
  2. On sites where sea buckthorn regrows after cutting, stumps or regrowth must be treated with herbicide. This adds to the costs and overall work commitment. Old plants (eg 3m, 10′ high) are often killed by cutting, especially in damp conditions. But regrowth is likely from plants 1-2m (3′-6′) high, while smaller plants tend to sucker profusely after cutting.
  3. Clumps which are cut may regenerate rapidly around the edges. The peripheral stolons are stimulated by the cutting of the older part of the plant.

Procedural points:

  1. Use a bow saw or power chain saw on large plants which have lost their lower branches and a scrub cutter on plants with stems under about 100mm (4″) diameter which are well furnished with low branches and are hard to get at using other tools. Cut small, whippy stems with pruning shears or dig them up by the roots.
  2. Cut sea buckthorn near ground level unless the stumps are to be grubbed up afterwards, in which case stems should be cut off at about 1m (3′) level so they can be more easily pulled or winched out.
  3. When using the scrub cutter, cut with a scythe-like motion to fell the small stems of young colonies and the margins of the main stands. Once you have opened up a ‘face’, work around the stand in an anti-clockwise direction (if the scrub-cutter blade turns anti-clockwise), cutting uphill on steep slopes or round and round an level ground. Hold the cutter in front and to your left and advance along the ‘face’ to the right so that the cut stems fall clear of you after you have passed. Cut with the part of the blade between 12 o’clock and 3 o’clock as you view it. Rest after each swath, or let someone else take over cutting for a while. It is dangerous to work too long without a break.
    After finishing a swath, throw or fork the cuttings clear to leave a space at least as wide as the height of the next shrubs to be cut. This insures an unimpeded work area when cutting the next swath. Where the sea buckthorn has been bent by the wind or is tangled with brambles or climbers, work slowly, cutting each stem into lengths and pulling it out from the face by hand. Anyone helping to clear up while the scrub cutter is in use should stay at least 5m (15′) away from the operator.
    Carry 8 or 10 sharp scrub cutter blades with you each day, since they can dull in as little as half an hour in sandy conditions. It is not practical to sharpen these blades in the field, and a dull blade is tiring and dangerous to use.
  4. You can reduce the extent of suckering from cut stands by chopping through the horizontal roots at the margins of the stand with a spade.
  5. Dispose of cuttings by piling them in windrows for burning or to rot down or by re-using them elsewhere for dune stabilisation or access control purposes. It is essential to clear up the cuttings if you plan a follow-up spraying programme. A bulldozer can be used to pile up the cuttings quickly and safety. On ground too steep for the ‘dozer’, volunteers can pitchfork the cuttings downhill to the machine.
    Leave cuttings for several weeks to dry out. It is best to cut the oldest stands first to give them the longest time to season. They will then burn easily without sparking and leave only a small line of ash. Avoid burning on a very windy day. Cuttings also need to season if they are ‘planted’ in dead hedges, to insure that the replanted stems do not root. Finish burning by the end of March, otherwise the brush piles will be occupied by nesting birds.

Grubbing-up

Advantages:

  1. Grubbing-up, if done with care, largely prevents problems of regrowth although spot-treatment is often necessary for surviving suckers.
  2. Grubbing-up can be done by hand or machine depending on the size of the problem.

Disadvantages:

  1. Grubbing-up by hand is slow.
  2. Uprooting by machine is unselective and can damage the soil and produce erosion. However, this may be balanced by the benefit gained from disturbing the seed bank buried within the soil.

Procedural points:

  1. First-year seedlings are soft and spineless and can be pulled up by hand. With older seedlings and suckers you need a spade, garden fork or mattock to get up the roots, which regrow into new plants if they are left in the ground.
    For small, shallow-rooted plants one person should dig around the root-plate while another pulls on the stem. Larger plants may need to be hauled free using a hand winch.
  2. The root system may extend up to 2m (6′) beyond the visible margin of the clump. Regrowth from the periphery is vigorous, so care must be taken to remove as much as possible. This is not easy however, as the roots are slender and brittle.
  3. Shake as much of the soil as possible from stumps and roots so that it falls back in the hole. This makes the plant material lighter and easier to burn and also reduces soil disturbance.
  4. A bulldozer or tractor with front plate can push over stems of almost any size. The machine must have a closed cab to protect the operator, who should push the material into windrows or leave it in place for volunteers to cut and drag away. At Ainsdale NNR, a low ground pressure bulldozer has been used successfully to uproot bushes and push them into a pile for burning. This method has proved quick and cheap, with good recovery of desirable dune species, and has been the standard method for some years.
  5. At Murlough NNR, a tractor-mounted ‘grubber’ was used, which could clear the roots down to their normal maximum depth of 500mm (18″). Large stumps, or those on steep slopes, were removed with tractor and chain. Inaccessible areas were cleared by hand using mattocks.
  6. Dispose of grubbed-up material in the same way as with cuttings.

Burning standing material

Advantages:

  1. Where live sea buckthorn can be burnt it is a low-cost method of disposal.
  2. Burning can clear sizeable areas quickly.

Disadvantages:

  1. Burning is hazardous and must be done with great care to prevent it getting out of hand.
  2. Burning is very destructive to wildlife, especially ground flora and fauna. If at all possible, burning should be done in winter or early spring (by the end of March at the latest), before the main flowering and nesting season. This is also usually required by stubble-burning (swaling) regulations. But at this season live sea buckthorn is much harder to set alight than in dry periods. If summer burning is essential, it may be possible to get the permission of the County Agricultural Executive Committee.
  3. Dead, unsightly stems are likely to remain standing after a burn and should be cleared if amenity is an important consideration.
  4. Regeneration can occur from burnt and apparently dead stems.

Procedural points:

  1. Carry out burning only in a very light breeze. The burn should run into the wind for control.
  2. Station people around the are with fire beaters to make sure that the fire does not get out of hand.
  3. Burn only a small area (eg 1 acre, 0.4 hectare) at any one time, for safety and to minimise destruction of wildlife.

Herbicides

Advantages:

  1. Herbicidal treatment can be effective in controlling growth. However, for complete eradication, repeated spraying of regrowth over many years may be needed, as the plant may continue to sprout from underground stems.
  2. Treatment can be done by one or two people.

Disadvantages:

  1. The effects of herbicides on the environment are not fully understood and some herbicides may be hazardous to the operator. It is essential to take great care, especially when handling and mixing concentrates. If a volunteer group cannot equip itself with adequate protective clothing and insure a high degree of safety awareness, it should not use herbicides.
  2. Chemicals and spray equipment are fairly costly.
  3. Dead material remains standing and is unsightly unless cut down. Small stems of young plants may be left standing to form a windbreak which can reduce soil erosion on dunes.

Procedural points:

  1. Before its ban by many authorities, 2,4,5-T was formerly used effectively on some dune sites to control buckthorn. However, at Murlough NNR, it was found that stump application appeared to encourage the plant to spread more rapidly around the periphery of the clump, and use was therefore abandoned.
  2. Results from experimental work at Saltfleetby NNR (Marrs, in Doody, 1985) have indicated that Garlon 2 is likely to be the most effective herbicide available at present for controlling sea buckthorn. Garlon 2 has been used successfully at Ainsdale NNR, to spot-spray bushes in May and June. Treatment is used to kill regrowth from cut stumps, and to control the spread of clumps where it is desirable to keep the older central part for nesting birds and passerines. Further details on Garlon 2 are available from ICI Plant Protection, Woolmead House, Bear Lane, Farnham, Surrey GU9 7UB.
  3. Glyphosate, a translocated non-selective herbicide, has been tried at Murlough NNR. It was found that unless every leaf was sprayed, the effect was patchy, as the herbicide did not appear to be translocated throughout the plant.
  4. Ultra-low volume sprayers are not generally recommended, as although these save on transporting large volumes of water to possibly inaccessible areas, their small droplet size means they can only be safely used on very still days.
  5. Ammonium sulphamate may be used on larger plants where foliar treatment is impractical. It comes in crystal form and is distributed as ‘Amcide’ by Battle, Hayward and Bower Ltd, Victoria Chemical Works, Allenby Road Industrial Estate, Lincoln LN3 4NP. Frill-girdle standing stems near ground level and apply the neat chemical to the cut area. You can also use ammonium sulphamate on cut stumps, either neat or diluted in water, within forty-eight hours of cutting. Dilution should be at a rate of 41b of chemical per gallon of water (0.4kg/l). A wetting agent (eg household detergent) may be added to aid penetration. Wet the stumps thoroughly down to the ground and either mark them with a dye or frill them with a billhook to show that they have been treated.
    Ammonium sulphamate is highly corrosive to most metals. Use a plastic bucket to carry the neat chemical or diluted herbicide for painting on stumps, or pour the solution out of an all-plastic watering can with a plastic rose.

Mowing

Advantages:

  1. Mowing is quick and efficient.
  2. Mowing is suitable for a wide range of plant sizes, depending on the available machinery.
  3. In most cases, mown material can be left in place to rot down.

Disadvantages:

  1. Regrowth is likely except from old plants or on sites where sea buckthorn does not flourish. The effect of mowing may be to produce a ‘carpet’ of suckers the next year. Even annual mowing may not eradicate the suckers and new seedlings will rapidly invade the area unless rank grasses grow up which choke them out.
  2. Mowing is relatively unselective.
  3. Mowing machines cannot be used on very steep terrain. Heavy-duty machines may cause unacceptable erosion on fragile dune soils, even on slopes where they would otherwise be able to operate.

Procedural points:

  1. For control of young suckers and seedlings, an ordinary rotary mower is suitable on regular, firm ground while a ‘Flymo’ is better on rougher ground.
  2. Where large areas are to be mown or where the stems are too big for a small mower, a tractor-mounted flail or reciprocating mower-arm works well. See Hedging – Machine trimming for details.
  3. Even trees up to 3.6m (12′) tall can be cut up with a tractor-mounted heavy-duty rotary mower such as a ‘Bush-hog’, provided the tractor has a front plate and can push the tree over first. The tractor must have a closed cab to protect the operator. For details, see Wittering (1974).

Treatment after clearance

It is most important that efforts are made to encourage the return of typical duneland species after the clearance of sea buckthorn, and also that vigilance is maintained in clearing regrowth and seedlings of buckthorn.

  1. Rake up and burn as much as possible of the leaf litter formed over the years by the buckthorn.
  2. At Murlough NNR, it has been found that by ploughing the surface of the dune, the dormant seed bank of duneland species is activated. A good response from winter annual plants has occurred by clearing buckthorn in the summer, so allowing the newly ripened seed to germinate quickly. The seed of winter annuals appears to have a short period of viability in the soil.
  3. By the September following a winter of clearance at Murlough NNR, 79 species of flowering plants were recorded in the 2 1/2 hectare area previously dominated by buckthorn. Growth of many species was luxuriant, due to the high nitrogen status of the soil. Among the many interesting species were several normally found only on the strand line. Some ‘weed’ species also occurred, a few being new to the reserve. In the spring and summer of the following year there was a spectacular display of flowers in the cleared areas. Flowering dune annuals dominated, with only a few ‘weed’ species surviving from the previous year.
  4. Regeneration of dune vegetation was poorest in the areas where the sea buckthorn had been over 15 years old. This may be due to the thick leaf litter producing acids which destroyed the buried seeds. On the less altered soils cleared of younger buckthorn, the recolonising vegetation is developing towards the typical community of nutrient-deficient soils. For a full account, see Ellis (edit. 1983).
  5. Ranwell (1972) states that mowing and removal of clippings is necessary on restored areas to reduce the nutrient levels.

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