Various cultural factors influence the biological and economic potentials of Eucalyptus grandis and slash pine as biomass energy crops for southern and northern Florida, respectively. On muck soil, superior E. grandis progenies may produce up to 70 dry Mg ha−1 in 24 months. However, coppicing success on muck soil has been inconsistent. Clones superior in frost-resilience and vigor and propagated as rooted cuttings have increased productivity potential on sandy soils. Break-even costs GJ−1 range from just under US$2 for E. grandis short-rotation intensive culture (SRIC) on muck soils (10 000 trees ha−1 with a 6-year rotation, i.e. seedling/coppice/coppice cycles of 2 years each) to US$4.00 GJ−1 on sandy soils. Planting density, but not coppice rotation, is sensitive to the discount factor. Through 8 years, slash pine yields responded well to soil amendments on typical sites and to high planting densities. Fertilization and vegetation control increased productivity some seven times over conventional culture through 5 years. For slash pine SRIC, higher discount rates increased initial stocking levels and shortened rotations. Break-even costs for slash pine are within the range of values estimated for E. grandis.