Genus Betula Species nigra Cultivar 'BNMTF' Dura-HeatÂ® Common Name Dura-HeatÂ® River Birch Patent ID Height 40 to 50 Feet Spread 30 to 35 Feet Habit Multi-stemmed tree, upright to rounded crown. Moderate to rapid growth rate. Zone 4 to 9 Culture Full sun to partial shade. Flower Flower Color Foliage Wedge shaped, lustrous dark green turning buttery yellow in fall. Deciduous. Category: Shade Tree Description Holds up better than other birch cultivars during heat stress common in the south.