TREES FOR WATER CATCHMENT AREAS 155 



in height growth and gets above the frost zone. Alder has 

 one great advantage in that it is scarcely ever attacked by- 

 rabbits, and may be planted without the expense of wire 

 netting. It has been found useful in planting pit-mounds, 

 slag-heaps, etc.; and this illustrates the fact that alder, while 

 most successful in wet soils, is not confined to that situation, 

 as it grows even in chalk. 



The wood of alder is at the present time of little im- 

 portance ; but it is still used for making clog-soles, backs of 

 brushes, mop and rake handles,inferior cigar boxes, hat blocks, 

 etc. It is very durable under water, and may be used for piles. 



Grey Alder. — The grey or white alder {Alnus incana) 

 is not a native of Britain, but is widely spread on the 

 continent, attaining its largest size, about 70 feet in height, 

 in Sweden. It is considerably hardier than the common 

 alder, and is remarkable for its vigorous growth in youth 

 and its indifference to the nature of the soil. It grows 

 on gravel and on cold clay, and flourishes in the frostiest 

 localities. It is used in the Swiss Alps for preliminary 

 planting in difficult situations at high altitudes, where as 

 soon as it has formed canopy, it is underplanted with beech 

 or silver fir, which are destined to be the final crop. It 

 may be used for a similar purpose in this country, especi- 

 ally for killing grass in low-lying frosty situations. When 

 this is effected, the grey alder may be heavily thinned, and 

 common spruce or Sitka spruce be planted under the 

 protection of the trees that are left. Grey alder can 

 also be used in planting pit-mounds, gravelly borders of 

 streams, disused quarries, etc. As a permanent crop, it is 

 best treated as coppice on a long rotation, of about 

 30 years. Grey alder has been used with great success 

 in the planting of pit-mounds in Belgium and France, but 

 has not done quite so well as the common alder on the 

 mounds in Staffordshire. Here it is, however, making good 

 fertilising nodules on its roots, and is expected ultimately 

 to thrive well. See Martineau, in British Association Report, 

 Newcastle-on-Tyne, 1916, p. 494. 



