Accelerated Production of Tree-form Crapemyrtle

Abstract

Most cultivars of crapemyrtle are vigorous growers under nursery conditions; however, some cultivars begin flowering by early summer, resulting in suppressed vegetative growth, particularly height growth, a problem often compounded by heavy fruit set later in the growing season. Pruning of inflorescences is labor-intensive and results in rapid re-bloom. For production of standard (single trunk) or multi-trunk tree-forms of crapemyrtle with 112 cm to 183 cm of clear trunk, pruning exacerbates the problem by stimulating new shoot formation, often from the main trunk. The effects of production light level on growth of crapemyrtle were evaluated as a means of accelerating the development of tree-form crapemyrtles. Plant height of ‘Fantasy’, ‘Carolina Beauty’, and ‘Tuscarora’ was greater when grown under 50% or 80% shade than when grown in full sun. Trunk diameter or caliper of Dynamite™ v i and ‘Tuscarora’ was greatest when grown in full sun, while production light level had no effect on caliper of ‘Carolina Beauty’. Dynamite™, ‘Muskogee’, ‘Natchez’, and ‘Tuscarora’ grown in Oregon were taller than plants in Alabama, while plants generally had less caliper in Oregon. ‘Muskogee’ and ‘Natchez’ in both locations were generally taller when grown under 50% shade than plants in full sun. Caliper of ‘Natchez’ in both locations was less when plants were grown under shade, while caliper of ‘Muskogee’ and ‘Tuscarora’ was not affected by production light level. Flowering of crapemyrtles grown under shade in Alabama was delayed or suppressed in each experiment, while no plants in Oregon flowered the first year of production. In another study, the effects of production light level on coppicing and coppice timing were evaluated as means of accelerating the development of tree-form crapemyrtles. Coppiced plants were generally taller when grown under lower light levels, while coppicing crapemyrtle while dormant resulted in greater height and stem cross-sectional area than delaying until the growing season, with no effect on survival. Visually, coppiced plants had more uniform shoot diameters and less branching than non-coppiced plants. Dynamite™ and ‘Potomac’ grown in tree shelters were taller at the end of two experiments, while caliper was minimally affected. All plants grown in tree shelters flowered later than unsheltered plants and appeared to have straighter, more upright trunks with minimal lateral shoot development.