Establishment and winter survival of Leucaena spp. and Gliricidia sepium in the cold subtropics.
A summary account of field trials in Florida with L. diversifolia accession K156 and, L. diversifolia × L. leucocephala accession K743 (both of which are reported as better adapted to cool climates than L. leucocephala itself), L. leucocephala accession K8 and G. sepium (which is better adapted to acid soil conditions than L. leucocephala). Seeds of all Leucaena spp. were hot water scarified, and seeds of all species inoculated (with leucaena and peanut inoculant) before hand sowing 2.5-5 cm deep in 6×3 m rows in June 1986. The site was a fine sand soil fertilized [with PK] before planting. Emergence date, plant ht., flowering date, frost tolerance and winter survival were recorded. Emergence of G. sepium was best, at 57%. Only 2% of L. diversifolia emerged, possibly because of dry soil conditions (no irrigation was done). Av. ht. 8 wk after planting was the same for all species. G. sepium grew hardly at all after the initial phase, with most plants reaching <1 m in ht. and older leaves becoming chlorotic and leaflets dropping off, suggesting nitrogen deficiency. Only one plant flowered (L. diversifolia × L. leucocephala) but there was no pod development. The 3 Leucaena spp. were defoliated by a series of frosts (min. -4°C) in Jan., but all resprouted. G. sepium took much longer to resprout, and was also damaged (defoliated) earlier by temperatures of <4°C in Dec. Survival in May 1987 was best in L. leucocephala (92%) followed by L. diversifolia × L. leucocephala (85%), G. sepium (66%) and L. diversifolia (50%, from an emergence of only 4 plants).