August, 1908. J 



111 



Saps and Exudations. 



Another important question in regard 

 to rubber planting is that of dis- 

 tance between the trees. Considerable 

 difference of opinion exists in this regard, 

 and as is the case with Hevea planters, 

 distances varying from 6x6 feet to 30 x 30 

 feet have their advocates among planters 

 of Castilloa. 



I have concluded from experiments 

 conducted with a view towards ascertain- 

 ing the relation of distance between the 

 trees, and the weekly, monthly and 

 annual increment of trunk growth, that 

 as soon as the roots of the trees touch 

 and become intermatted the growth of 

 the trees is impaired. But on the other 

 hand, we know that if the Castilloa trees 

 are planted very far apart their growth 

 is stunted, and, when the trees become 

 older, their bark is exposed to the heat 

 of the sun and to evaporation caused by 

 dry winds passing through the planta- 

 tion. The result of this is that the bark 

 cracks, the latex vessels shrivel, and no 

 latex can be obtained. We then say 

 that the trees are " sunburned." 



The question then arises : at what 

 distance are we to plant ? I decidedly 

 condemn too close planting, as it leads to 

 a disproportionately whip-like growth 

 of the trunk. I would also emphatically 

 warn against too open planting. I think 

 the error of the latter practice is con- 

 clusively proven by the following in- 

 stance that has come under my observa- 

 tion. Two years ago I visited a large 

 Castilloa plantation on which the trees 

 had been planted 21x24 feet apart. The 

 trees were five years old, and investiga- 

 tion disclosed the fact that a great 

 percentage of the trees, especially those 

 which had been growing on dry knolls 

 or exposed places, had a bark very 

 rough, scaly and full of longitudinal 

 fissures. The inner bark, in which the 

 latex vessels are situated, was very dry, 

 and the latex in the ducts had coagu- 

 lated. In many places on the bark 

 exudation of latex had taken place, and 

 big drops or tears of latex had formed 

 scrap rubber. The only way in which 

 this condition of the trees could be 

 remedied, was to allow the weeds to 

 grow up and underbush to develop. 

 This vegetation shades the trunk, and in 

 due time the bark is formed and the old 

 is thrown off. This process takes at 

 least two years, and is successful only in 

 case the cambium has not been injured. 



In deciding about the distance at 

 which to plant we have to take the 

 following two primary factors into con- 

 sideration. The trees must not stand so 

 close as to impede the growth of each 

 other, and they must not be far enough 

 apart to leave the trunks exposed to sun 

 and wind. 



From the above we obtain an indica- 

 tion pointing towards the method we 

 ought to follow, i.e., close planting and 

 subsequent gradual thinning, according 

 to the requirements of the trees. Be- 

 sides fulfilling some of the conditions 

 leading to a successful development of 

 the rubber stand, the method of close 

 planting has other advantages. It 

 permits of a thorough system of selec- 

 tion which is not possible under the 

 method of open planting in permanent 

 situations. From a financial point of 

 view close planting i-, decidedly superior 

 to any other method. It has been 

 proved that by proper management the 

 intermediate rubber trees, which are not 

 supposed to remain permanently in the 

 stand, can be made to produce a suffi- 

 cient quantity of rubber to render the 

 system very profitable, before the 

 permanent trees can be considered pro- 

 ductive. By close planting the danger 

 of failures in the stand is reduced almost 

 to nil, and this is important to the 

 planter, as filling up failures in a young 

 forest is both expensive and precarious. 



There is always a temptation to leave 

 too many trees, in order to provide for a 

 big side crop, but this should naturallv 

 be resisted. A heavy thinning comes to 

 the assistance of the best specimens of 

 growth, and it must on no account be 

 omitted or postponed. It is extremely 

 difficult to lay down any definite rules 

 as to thinning operations, but it has 

 been conclusively proved that the 

 general rules applied in scientific for- 

 estry in regard to silvicultural operations 

 are fully applicable to the cultivated 

 rubber trees. Rubber planting is 

 nothing else than silviculture, and we 

 should take our lessons from ordinary 

 common sense, and from results obtained 

 from the extensive experience of the 

 forest planter, naturally with due atten- 

 tion paid to the particular condi- 

 tions obtained in tne Tropics and the 

 peculiar nature of the rubber tree. 



The method of propagating Castilloa 

 first employed was to sow the seeds in 

 nurseries, and when the seedlings were 

 four to six months old they were trans- 

 planted. "Very often, however, trans- 

 planting was not done before a year 

 after sowing. The plants were , then 

 from 5 to 12 feet high. The seedlings 

 were cut five or six inches below the 

 surface, and topped, leaving a pole some 

 three feet long. Tied into bundles these 

 poles were carried to the field. With a 

 pointed stake, holes were made in the 

 ground about one foot deep, and the 

 pole placed in the hole and the soil 

 pressed close to the stem. When this 

 planting was done carefully, and if rain 

 fell within the next two or three days, 



