September 



IRISH GARDENING. 



133 



Tree Growth in Bog Land. 



To the current issue of the Journal of the Depart- 

 ment of Agriculture Mr. A. C. Forbes contributes 

 an interesting- and sugfg-estive article under the 

 above title. He begins by telling- us that "the area of 

 bog in Ireland amounts to about 934,000 acres, or nearly 

 5 per cent, of the total surface. The greater part of this 

 area lies on the West coast and through the Central 

 Plain, and consists of sphagnum bog- many feet in thick- 

 ness, and completely saturated with water throughout. 

 In addition to this 'high ' hog, as it is termed, which is 

 utilised at the present time for fuel generally throughout 

 Ireland, a very large area of mountain land, especially 

 in the west and north, is covered with a layer of wet 

 peat, varying in depth from a few inches to several feet, 

 and in the case of hollows and depressions, forming 

 practically the same class of peat as that found on the 

 deeper bogs at lower levels." 



.•\s to the utilisation of bogf land for crops many 

 attempts have been made, and, although to some extent 

 successful in the case of partially cut-away bog 

 lands, all attempts at the cultivation of high bog have 

 ended in failure. In the former case drainage and 

 manuring are possible and more or less effective, 

 but in the latter, owing to the presence of so much 

 sphagnum or bog-moss, it is impossible to drain, and 

 so manuring is useless, and hence the soil remains 

 poor, while the presence of acid renders it a most 

 unfit medium for the roots of either ordinary cultivated 

 crops or forest trees. 



There is convincing evidence, however, to prove that 

 at one time in Ireland trees grew over the bog-lands, as 

 the stumps of Scots pine and birch are frequently found 

 in the peat, their positions clearly indicating that they 

 grew and died there, and not on the mineral soil below 

 the peat. If ti-ees gfrew there once on a time, why not 

 now? Mr. Forbes answers the question in this way : — 

 " The difficulty." he says, "lies in explaining, however, 

 the equally obvious fact that the trees which existed 

 over such wide areas of bog- throughout the British Isles 

 again disappeared. While it is possible that their de- 

 struction ma}- have been partially brought about by the 

 agency of early races of men. the definite sequence in the 

 layers of peat and tree stumps, which has been recently 

 established beyond a doubt by various investigators, 

 points to a climatic change rather than anything else. 

 Geologists have good grounds for belief that alterna- 

 tions of wet and dry periods have occurred since the 

 deeper bogs commenced to grow. The tree growth 

 corresponds to a dry period, the disappearance of this 

 growth to a wet cycle. As the bog dries, and the 

 natural bog flora dwindles awaj', a certain amount of 

 weathering takes place on the surface, involving the 

 decay and disappearance of the sphagnum, and exposing 

 the black and more solid peat below. As the latter is 

 gradually converted into vegetable mould or black 

 earth, it becomes capable of supporting a growth of 

 grass, bracken, various species of trees, &c., and, in 

 time, may acquire a complete covering of forest growth. 

 A return to wetter conditions, enabling the sphagnum 

 to again cover the surface beneath the trees, restarts 

 the bog into growth, and a growth of timber which has, 

 perhaps, existed on it for hundreds of years is gradually 



killed out by the saturation and souring of the surface, 

 and the bog again becomes treeless. In the above 

 manner it is conceivable that bogs might show a suc- 

 cession of forest crops separated by growths of peat, 

 and indicating that drainage, or the lack of it, as the 

 case may be, was the only determining factor in the 

 changes which have taken place." 



Another reason for the poverty of high bog lies in the 

 fact that the water of saturation contains such an ex- 

 tremely low percentage of minerals that trees are starved 

 out tor the lack of them. The deeper the bog the poorer 

 it is in minerals, hence as the accumulations of peat 

 deepen the tree flora alters. For example, the Scots 

 pine in a growing bog^ is succeeded by the birch, which 

 requires a lower percentage of minerals, and when in 

 turn the birch disappears its place is taken by the still 

 less exacting- willows. 



The initial difficulty, then, in planting high bog is to 

 get rid of the stagnant water that saturates the mass, 

 and the author shows how difficult it is to do this unless 

 at very great expense. In partially cut-away bog, where 

 the newer and more spongy deposits have been removed, 

 the task is not so difficult, and there are many places 

 in Ireland where trees are growing upon peat ten to 

 twenty feet deep. 



As to the species of tree suitable for bog-planting Mr. 

 Forbes says that while they are many in number only a 

 few "succeed in recently drained bog. Birch, poplar, 

 alder, pines and spruces, and occasionally silver firs, 

 larch, Douglas firs. Thuiagigantea, &.c.,mayall be planted 

 on partly cut-away bog with a fair prospect of success, 

 but much depends upon the progress made in the con- 

 version of the peat into vegetable mould. The most 

 successful on high bog are birch, mountain pine, mari- 

 time pine, Black and White American spruces, Sitka, 

 and Colorado spruce. With the exception of birch, 

 Sitka spruce, and maritime pine, none of these is likely 

 to produce commercial timber. Birch grown in large 

 quantities might form a profitable crop on peat in the 

 long run, as its powers of reproduction from seed and 

 stool shoots are good. So far as can be judged from 

 present appearances, Sitka spruce may prove to be the 

 most successful of all trees for growing into timber on 

 high bogs, but more time is required to confirm this 

 opinion. Maritime, Corsican, Weymouth, Austrian and 

 Scots pines may all be seen growing into .small timber 

 on high bog, and the first named is probably the most 

 successful. The tree, however, most commonly asso- 

 ciated with Irish bogs is Scots pine. Partly owing to 

 the freedom with which natural seedlings come up on 

 bog, partly to its power of surviving under the acid 

 surface conditions when planted, this species is far 

 more universally represented than any other. In spite 

 of its comparative longevity, however, it is no greater 

 success as a timber tree than others, although it grows 

 to large dimensions on cut-away bog. No species has, 

 however, yet produced a crop of timber on high bog 

 which could be considered as clearly establishing the 

 fact that bog-planting is a financial success, and, until 

 this has been demonstrated beyond all doubt, it would 

 be unwise to regard it in any other light than that of 

 an experiment, or as a means of reclaiming useless 

 land. 



" Apart from the financial point of view, it is possible 



