Destruction of Gorse and Blackberry.

New Zealand Journal of Agriculture, Volume 58, Issue 2, 20 February 1939, Page 111

Destruction of Gorse and Blackberry.

Methods of Eradication and Control

J. E. BELL,

, Instructor in Agriculture, Auckland.

iiiiiiiiiiHiiiiiiiiiiiiiiiiniiiiimiiii I The destruction of gorse I and blackberry is a vital | problem on many farms in New Zealand. While no completely satisfactory method of eradication has yet been found, there are certain steps which may be undertaken to alleviate the position. These methods are freely examined in this article, and many helpful | recommendations are made. I I I I I I II I I I II I 1 11 I ®

ORSE and blackberry are two prickly weeds well endowed by prickly weeds well endowed by nature in their struggle for existence, and they need no formal introduction to the New Zealand farmer. Blackberry grows most vigorously in wet ■ climates and moist soils, being most common in Westland and in the North Island. Gorse prevails everywhere. Both are very difficult to kill, and arguments as to which is harder to eradicate are common. The fight with these weeds is going on continuously. Farms are neglected, becoming therefore infested, and infested farms are gradually won back to freedom from gorse and blackberry —often enough a lifetime struggle. Gorse gained a foothold in Canterbury because the early settlers required stockproof hedges. In the absence of timber and wire, gorse fences, established from seed sown on raised banks, have served and continue to serve a useful purpose. In parts of Auckland Province gorse was sown for the provision of sheep feed and to make live hedges. ' Blackberry was introduced because of the lusciousness of its berries. Both plants grew extremely —better, probably, than in their

native landand in a young colony with a small population they have quickly spread out of control. ; 1- h Protected by Thorns. Gorse and blackberry are perennial plants, and are protected by thorns from man and beast. Blackberry produces long stems which often travel several feet, when they anchor themselves to the

ground anew by means of roots before continuing. Thus, .large bushes of this plant are formed consisting of an almost impenetrable mass of stems and leaves. Birds spread the seed through their liking for the berries. Gorse spreads only by means of its seed, which is notorious for the length of time it will retain its germinating-powers, and from which it yields a heavy annual crop. The chief enemy to the spread of these two vigorous weeds is a good, tight sole of grass. Gorse and blackberry do not encroach rapidly where the pastures are highly productive. '■ Where the pasture is open and poor, gorse and blackberry seedlings establish, and, spreading rapidly, entail a considerable amount of work in their, control. The most common method of controlling blackberry is by cutting it close to the ground, and for gorse by cutting and grubbing. In the past the cutting was usually done with a slasher, but now the scrub bar with the safety release mechanism working behind a tractor has resulted in acres being mown in this way. Gorse stems up to the thickness of a thumb can be cut in this manner. Lately

other methods of control, have arisen. Some farmers have acclaimed these as successful, while others have condemned them as useless. ■ The Plant Itself. Before discussing some of these methods let us examine the gorse-plant. First a seedling with soft clover-like leaves and later a spiney, small plant an inch or so high, it still later grows into a plant with stout, upright, Woody stems with sharp prickles, growing up to 7 ft. or 8 ft. high. In time it grows old and dies. < The plant is easily killed when it is very young and when it is old. The effect of merely cutting it down with a slasher will frequently kill “ old man gorse.” The young gorse-plant can often be destroyed by fire before it flowers and by grazing stock nibbling it close to the ground. ; However, when the gorseplant has flowered once, and particularly when it has flowered twice, it is fully vigorous and much more difficult to kill. Hence we have the conflicting reports on the effectiveness of different methods of gorse-destruction.

Vigorous gorse can be destroyed by grubbing it out, severing the tap root about 1 in. below the crown. Once the tap-root is cut it is preferable to pull the plant out with a gloved hand and replace the turf, for the disturbed soil proves an excellent bed for. the germination of the gorse-seeds which : lie in their thousands wherever gorse has flowered. Whether gorse has been cut or burnt it is a wise plan not to fire it, but to leave the cut vegetation to rot away. A wonderful seed-bed is provided if it is burnt, and thousands of gorse seedlings soon establish on the burn. Left alone, the cut vegetation does smother or - check some of the gorse. If the area is to be grubbed soon after the cutting the dead vegetation may interfere with this operation and may, of ’ necessity, be burnt; if the intention is to plough the area soon after cutting the gorse must be burnt. The burning can, advantageously at times, be delayed until regrowth appears from the old stumps, thus giving the gorse a second setback.

Burning of Gorse.

The burning of standing gorse probably does more harm to the grass and clover competing with the gorse than it does to the gorse itself. . The burning of any gorse where no useful purpose is served and where it is not intended to pursue the eradication process further is foolish. The behaviour of gorse would almost lead one to believe that it was evolved on the farm of the man who did much of his farming operations with the firestick. Every time mature gorse is fired more gorse is brought to life, which, in two years’ time, will be in full vigour of young adulthood. Chemicals have proved to be of little use in gorse-control. A 5-per-cent. solution of sodium chlorate will kill gorse seedlings in the soft-leaf stage, but let them develop spines, and two or three times the concentration is then required to effect a kill. Left until later, chlorate sprays do little harm. Attention has lately been drawn to the flame-thrower as a controllant of gorse. One farmer I know effected good control with one burning-off. The gorse, however, was " old man gorse,” and a match might have been equally effective. This patch of gorse had stock tracks running through it, and there was a good sole of grass, including much paspalum, under the tall gorse. After being burnt the area was shut up for hay, and no doubt the young 1 gorse seedlings, which would germinate profusely after the burn, were smothered by the vigorous grass-growth. Where the flame-thrower has attacked other gorse areas the victory has not been so easy. Figure 2 shows an area of gorse and blackberry which has had six flamethrowings. The farmer, Mr. T. Bowker, of Patumahoe, who has carried out the work, is very satisfied with what has been accomplished, for the gorse and blackberry were 5 ft. high twelve months before taking 'the photograph. The method adopted was : one which did the greatest damage , to the weed with the least expenditure. First, a light touch of the flame-thrower was given to all the accessible plants, and after this had gone brown the area was fired with a match. Flame-thrower’s Use. One of the attributes of the flamethrower is its ability to bring about a burn in this way at any season of the year. This enables the farmer to continue punishing the gorse by burning it at short intervals: A few weeks later, when new growth had- commenced, the flame- ' thrower was used to play on this and to kill the young gorse seedlings which came up. The gorse seedling is killed if just singed with the flame. Later, a fresh

attack was made on the accessible tall growth, followed, as before, by the match and a second playing of the flame-thrower to kill the gorse seedlings and check new growth. When the photograph was taken the area, which consists of about half an acre, had had six flame-throwings and was in a position to be handled by other methods. So far the work has cost 17s. 6d. for the 30 gallons of oil used. Nearly all of the gorse and much of the blackberry has been destroyed, and Fig. 3 shows a close-up of parts where the kill has been good. The more vigorous plants still remain, and blackberry appears to resist the flame-thrower more than gorse. Farmers sometimes take up farms badly infested with gorse. It is always better to tackle small areas at a time than to try and crush all the gorse at once. Grubbing, cutting the gorse, feeding hay on the poorly grassed portions, and top-dressing to thicken up the sward all tend to eliminate the gorse. The first step is to cut the gorse. This operation should take place in the autumn. Leave the gorse to lie and rot. Stock the area next winter with cattle and sheep if available, and feed much hay on the gorse area. The trampling of the cattle will injure the gorse and will make

a seed-bed for the grass and clover seed in the hay. The sheep will nibble at the gorse and keep it in check. Concentration of Efforts. Next spring begin grubbing all plants showing any sign of recovery, and apply a heavy dressing of fertilizer and lime, if necessary, to the area. Next year deal with another small area, going back with the grubber whenever necessary over the area previously tackled. If the work is concentrated in this manner, and the farmer reminds himself that what is in thick gorse cannot become worse infested and is better left alone than tackled in . a half-hearted fashion, then real progress will be made. A large area cut and burnt looks tidy, but is a large accomplishment for only a short time. Farmers hesitate to plough gorseinfested areas because of the danger of making a very fine bed for the gorseseed to germinate in their millions. Once he has ploughed he knows that he must continue with the cultivation until he has germinated almost every seedling and destroyed it. Once it has germinated, the young seedling is easily destroyed by cultivation and by a smothering crop. Autumn-sown crops, such as

Italian rye-grass and oats for winter grazing, are excellent for this purpose. Once the old gorse has been destroyed by the cultivation and the majority of the seeds germinated the area can be laid down to permanent pasture in the autumn. If the permanent grass is sown early . on a good firm seed-bed, with plenty of suitable fertilizer and lime so that it begins growth quickly, enabling the area to be stocked early by numerous grazing animals, the seedling gorse will suffer from the smothering effect of the fast-growing grass and from the trampling and nibbling of the numerous stock. If the grass is slow in developing and the growth is poor the gorse will grow out of the delicate baby stage before the stock are likely to harm it. It can be seen, therefore, that it is particularly important to sow permanent pasture only when conditions are likely to be ideal on gorse-seed-infested ground. Gorse as a Feed. Stock are fond of young gorse. . In the Karaka,' a district to the south of Manukau Harbour, gorse was once drilled on large estates for the provision of sheep feed on land that at that time was too poor to grow other crops. After grazing, the young gorse was destroyed

by ploughing it in. Unfortunately, some of it must have been left, because gorse was afterwards very prevalent in that district. On dry soils in dry climates the sowing of gorse-seed for sheep feed may still be of some value, but the plant has become such a nuisance that the very thought of it is horrifying to most farmers. Once gorse ages it is not liked by stock, which eat only the tender young shoots. Sheep are more fond of gorse than cattle, and are commonly used to control it, but all they do, however, is to keep it somewhat in check, except when it is . a seedling. Unaided by grubber or slasher and good grass-growth, gorse will outgrow the sheep’s efforts to keep it in check. Even in cold climates where feed is scarce in winter the gorse-plant will, besides providing young shoots for the sheep, gradually elongate its main stem and branches, until one day one young shoot grows beyond reach of the sheep. Horses

nibble gorse, but as a controlling factor they are never numerous enough to do much good. Stock, as controllers of gorse, are not very effective, because they will graze it hard only in times of feed-scarcity. At other times the gorse is left well alone, and, with its vigorous growth, it soon makes up for lost time. Grazed gorse protects its stems from damage by grazing stock by the springing-up of numerous branches bearing many. spines, so that it looks like a pin-cushion. Attacking Blackberry. Blackberry is generally attacked with the slasher or mowing-machine. Continual cutting will destroy blackberry, but generally it takes a long time and is then only accomplished with the aid of a good sole of grass. Grubbing does more harm to blackberry than cutting, but it is not so effective on this plant as on gorse. Nevertheless, it probably should be .more regularly employed.,

Heavy harrowing damages blackberry, for it lacerates the stems and is an easy and quick method of attacking blackberry a foot or so high in a pasture. Whatever method of attack is used, success will not be secured unless the grass pasture is encouraged by topdressing. Because of its vigorous growth, one of the best grasses to fight against gorse or blackberry is paspalum, which can be established by feeding paspalum hay on the area, or, better still, by seeding it and Lotus major among the bumt-out areas of blackberry in late November. Seeding is essential. where blackberry has grown so thick that all pasture plants have been smothered. Wherever the pasture is very poor, or where it does not exist, it pays, if possible, to plough blackberry-infested areas. Two or three ploughings with or without crops between will, with the cultivation, eradicate almost all of the blackberry. Cultivations should aim to bring the old blackberry roots to the surface, where

they can be dried and burnt or carted away. When the ground is clean, permanent pasture can be sown.

Sheep are fond of blackberry, and readily eat the young leaves. Blackberry growth is slow from May until September, but it grows rapidly in the spring. Sheep can keep blackberry in control in the winter, but in the spring, when other fodder is plentiful, they do not effect much control, and it is at this time that the farmer desires control.

Control by Goats.

Goats, as shown in Figs. 6 and 7, effect exceptionally good control of blackberry, and in winter will not allow a leaf to develop. In the spring the blackberry does develop a few leaves, but its vitality is low, and in the end goats, plus the top-dresser, will eliminate it. About two goats per acre are required on thickly-infested blackberry country. They eat very little grass while blackberry leaves are available.

The trouble with goats is their tendency to wander and help the neighbour out also. While this is often quite desirable, it does not encourage the purchase of goats for blackberry-control. Blackberry constitutes little difficulty on ploughable areas ; it is on inaccessible and unploughable country that blackberry is a menace. There the goat reigns supreme, and is the best method of eradication.

Blackberry is very frequently a nuisance on roadsides. Top-dressing and stocking cannot help to control the blackberry here, and on many farms cleared of blackberry and gorse the weediness of the roadside remains a problem.

Figure 8 shows the way one goat, tethered by a chain, is keeping the blackberry on the roadside controlled. Note the blackberry on the neighbour’s area, to which the goat is not allowed access. . All who have blackberry on their farms should read the interesting article by Mr. H. Guthrie Smith in the Journal of Agriculture, January, 1929, on “ Blackberry Control by Goats.”

Use of Sodium Chlorate.

The use of sodium chlorate deserves some mention. One spraying of ' a -per-cent, solution of sodium chlorate in May will result in the plant lying dormant for five or six months. Spraying thick blackberry every autumn with a 7-per-cent. solution for three years has resulted in most of the blackberry being killed, and has enabled a fair sole of grass to establish, which, top-dressed and with a few more sprayings, should result in clean pasture. Spraying appears to be more effective in controlling blackberry than does the flame-thrower. The reverse can be said for gorse.

In alluvial swamps blackberry grows to perfection, making masses of growth up to 7 ft. or 8 ft. high. Where the swamp is very wet, Glyceria aquatica (Poa aquatica) established among it will soon destroy the pest. I have watched for several years a . large swamp of 500 acres at Kopuku which was almost completely covered with dense blackberry. The Glyceria aquatica has been established' here and there throughout the swamp. It has taken charge of about half the swamp, having ousted the blackberry. It is still fighting against the remaining blackberry, and in a few years’ time there should be none in this swamp.

Glyceria aquatica is a grass with underground running stems or rhizomes. A plant established among the .blackberry sends out rhizomes in all directions, from which arise a forest of upright stems, bearing seed-heads. A circular patch of Glyceria aquatica soon develops, in which the blackberry is completely destroyed. Along the margin of the Glyceria aquatica and blackberry the fight goes on. The Glyceria aquatica grows up and, leaning against the blackberry with its dense foliage, gradually smothers it. In this way, much in the manner a man advances over blackberry using a plank, this grass will overcome blackberry twice the height of its leaves. Blackberry Smothered.

It advances against blackberry in a face, like a wave rolling over the shore,

the only difference being that the wave in this case is steady in its advancement and does not recede. Once smothered, the blackberry, however tall and thick it was, has no chance to re-appear. The tiny circle grows larger, and so steady is the advancement that the circular shape is often maintained until it is quite large in dimension. Glyceria aquatica can be aided in its attack against blackberry by firing along its line of march in the early spring.

In alluvial swamps which are not very wet, even where the ground is not covered with water over winter, another grass assisted a little by cutting, will quickly smother blackberry . This grass is Phalaris arundinacea or reed-canary grass. This grass will also live where the water lies in the swamp 2 ft. deep in winter, but‘it appears more vigorous where the water is not so deep. Both these grasses are most surely established by plants, but seed sown in the ash of blackberry bushes in the spring often results in good strikes. Both plants are high yielding and palatable.

Glyceria aquatica is the higher yielder and more suitable for swamps where water lies deep over the winter, while Phalaris arundinacea, which is the more palatable of the two, is more suited for areas where water does not lie at all or does not lie deeply over the winter. Both plants withstand fairly heavy frost and, if well grazed, grow all the year round, but their heaviest growth occurs in the summer, when they out-yield other grasses. A swamp of 65 acres at Kopuku, once in dense blackberry and now carrying a dense growth of these two grasses, has been reported to graze over the summer months more than three hundred head of stock, the majority of which were milking cows.

Farmer Avoids Trouble with Club-root.

A farmer on the Taieri has had a paddock under cultivation for the past sixteen years. Every second year it has been in mixed brassicas and mangels. Club-root is hard to find in most parts of the crop. The farmer states that he has not been troubled with club-root in this paddock at any time. His programme is as follows : Following turnips the paddock is sown down to oats and peas for hay. After this has been cut the paddock is ploughed, worked down and sown in early autumn with oats. These are ploughed in during the spring and the paddock sown down with swedes, chou moellier, &c. This completes his two-year rotation. One ton of carbonate of lime is applied annually. All the brassicas are carted out of the paddock, being fed to the stock in stalls or grass paddocks. ■O’ 4" "fr