The effect of bottom heat on rooting Pinus patula and Pinus elliottii x Pinus caribaea stem cuttings in South Africa

Abstract

Five trials, testing the effect ofbottom heat on rooting, were set between January 1995 and December 1996 on P. patula and P. elliottii x P. caribaea cuttings as a method of improving root strike. In four out of five trials rooting percentages improved with the addition of bottom heat at optimal temperatures and in all trials, where root dry mass was assessed, bottom heat had a positive influence on root dry mass irrespective of season. The increase in root dry mass ranged between 97% and 166 %. In one trial, where cuttings were set in the warmest months of the year, rooting remained unchanged. Rooting declined for those treatments where average media temperatures were raised to extreme levels (>30° C). Optimum media temperatures, during the period of root initiation, were found to range between 25°C and 28°C. Rooting media temperature was also found to influence the amount of stem decay and basal callusing. Future research should concentrate on the relationship between moisture and heat requirements during rooting.