Lagerstroemia cold hardiness

The assessment of the crop's cold hardiness is based on the root system's ability to survive soil freezing and the resilience of the aerial shoots to cambium damage. Most species are sensitive to temperatures below -10...-15°C, whereas modern hybrids, such as 'Tonto' or 'Sioux', can withstand frosts down to -23°C (zone 6a/6b). If the aerial part dies back, the plant often recovers from the roots, which allows it to bloom on current-season growth.

The plant's cold hardiness directly depends on wood maturation during the summer period. A lack of accumulated growing degree days results in shoots failing to lignify, which critically reduces resistance to sub-zero temperatures. For this reason, agrotechnical practices such as pruning are completed by August to prevent the stimulation of immature shoot growth before winter.