98 
PURE AND MIXED PLANTING. 
PURE AND MIXED PLANTING. 
The eucalypts are all light demanders. If we plant rapid growers and slow 
growers together, the former will overtop and suppress the latter. A similar result 
will follow if we plant rapid growing conifers and slow growing eucalypts 
together. There are two cases in which successful mixing is possible. The first 
is that where the trees included, whether all eucalypts or conifers and eucalypts, 
make equal annual height growth and can all keep their growing crowns clear. 
Such a mixture is ornamental, hut offers only doubtful economic advantages. The 
second case is that where the mixture consists of tall light-topped eucalypts and 
an under storey of some shade bearer. Here the difficulty is to find the shade 
bearer. In parts of Australia Pinus 'pinaster has been suggested as an under 
storey tree. We in New Zealand have talked about Cupressus macrocar pa in this 
connection. Trial plantings competently conducted in several localities will be 
needed in forming a safe judgment in either case. 
The practical test of all planting is the reaping. Small plantations of trees 
about farms and homesteads will probably he always managed somewhat 
irregularly. In the case of larger plantations and forests it appears to be an 
economic necessity that the trees shall be clear felled in successive blocks or sections. 
The whole of the product on each section must be removed within a limited period 
and the ground promptly restocked. Selective felling is very costly, and, unless 
skilfully done, very wasteful. If all the trees on a section are equal in maturity, 
they may all be cleared away in the same year. If they are at differing stages of 
maturity, the owner will be put to the expense and loss of selective felling. Even 
the reservation of seed trees for natural restocking of the ground is difficult and 
often not satisfactory. Only the experienced forester knows how to do it. 
But there are other aspects of the problem besides those that are severely 
practical and economic. Trees are living things with a long history of adaptation 
behind them. Where a species has been growing for thousands of years in association 
with certain other species and genera we must consider well before we isolate it 
or give it alien companions. In the unspoiled Eucalyptus forests of Tasmania 
and south-eastern Australia we see two well established forms of plant society in 
close contiguity to each other. The several species of Eucalyptus indigenous to a 
region, together with a few other large trees, blend in a society of giants. In any 
given locality one species may predominate, but others are nearly always present. 
That this blending of the giants has some mutual benefits may at least be assumed 
as probable. Spread out in all directions beneath the great timber trees is another 
society, whose units, representing many genera, are usually small and slender. 
Mingled with this undergrowth are many shade bearing acacias of humble 
dimensions. A forest floor so clothed and furnished is a natural laboratory 
producing humus and fixing nitrogen. It contributes immediately and continuously 
to the health and vigour of the great timber yielders, and assures for the soil 
perpetual fertility. 
Looking impartially at both the practical and biological aspects of our 
problem, we seem to be warranted in making three definite inferences as follows:— 
(a) Pure planting or nearly pure planting in sections will be found most 
convenient when the time comes to fell the trees and market the product, (b) 
