192 NATURAL REGENERATION 



underplanted with other trees, the undercrop will not be 

 mature by the time the Ash has to be cut ; but when grown 

 as a pure crop, it may often be partially cleared and an 

 undercrop of Ash obtained naturally. Both crops can then 

 grow as a two-storied high forest of Ash. When the older 

 trees are ready to be felled, in say 30 years' time, it will 

 be possible to obtain another undercrop of Ash in a few 

 years' time. Thus a perpetual two-storied high forest 

 may be grown. This natural regeneration of Ash will 

 hardly be possible on very moist soils, as there is almost 

 certain to be a strong growth of nettles and other weeds on 

 such soils, however dense the overwood of Ash may be kept. 



Ash may also be regenerated under the selection or 

 group systems ; and of these two, the latter is preferable. 



Sycamore and Norway Maple would seldom be profitable 

 as pure woods or as forming the greater part of a mixture. 

 They are not usually valuable enough when young ; there- 

 fore they should only be introduced sparingly by planting. 



Each of these trees, however, produce abundance of seed, 

 and readily regenerate naturally, if the soil be suitable. 



The Natural Regeneration of Corsican Pine or Scots 

 Pine is rare under a shelter wood, and should not be 

 attempted ; for the young trees are intolerant of shade, and 

 do not require the shelter. Also, when growing under mother 

 trees, they are very liable to fungus attacks of Hysterium 

 pinastri the leaf-shedding disease, and of Botrytis cinerea. 



Then again, any seedlings that have once suffered from 

 shade, never recover. 



If, however, it is attempted, only about 12 trees per acre 

 should be left, and these must all be removed by the time 

 the young crop is 3 or 4 years old. 



In most cases, the soil under a pure crop of Scots Pine 

 will be covered with rank grass, unless the crop were only 

 about 40 years old. This strong grass will appear even on 

 soils, which, when originally planted, were so poor as to 

 produce only heather ; since the soil will have become better 

 aerated, and somewhat enriched in plant food. 



The best method of naturally regenerating Scots Pine 



