Engineering Heat and Flood Tolerant Birches Through Grafting

Richard E. Bir and Thomas G. Ranney
North Carolina State University
Fletcher, NC

Tolerance of heat stress and flooding/poor soil drainage have been considered limiting factors in establishing commercially popular white barked birches in some locations. River birch (Betula nigra) has been found to be both more heat and flood tolerant than European (B. pendula), paper (B. papyrifera) and 'Whitespire' (B. populifolia) birches (1, 2).

To test whether river birch is compatible as a rootstock for 'Whitespire' birch, 'Whitespire' scions were grafted onto each of the four species as well as onto 'Whitespire,' grown in containers for one year then planted into a sandy clay loam soil with a mean percolation rate of 0.9 in. per hour at North Carolina State University's Mountain Horticultural Crops Research Station, in Fletcher, NC. Survival and trunk diameter following 3 growing seasons is shown in Table 1.

Plants of 'Whitespire' grafted on river birch were also included in the North Carolina Urban Tree Evaluation Program to determine actual performance under growing conditions in USDA Hardiness Zones 6-8 under a variety of soil drainage conditions. These plants performed well in all sites regardless of heat and soil drainage characterisitics. Ten year old trees have no signs fo graft incompatibility.

Table 1. Tree survival and trunk diameter (in.) following 3 seasons in the field for Betula 'Whitespire' grafted onto River Birch (B. nigra).

Rootstock% SurvivalTrunk diameter (in.)
River100 a2.44 ab
European80 a2.99 a
Paper80 a1.89 bc
Whitespire60 ab1.73 c
Szechuan30 b2.28 abc
Means followed by the same letter within a column are not significantly different, P = 0.05.

Literature cited:

  1. Ranney, T. G. and M. M. Peet. 1994. Heat tolerance of five taxa of birch (Betula): physiological responses to supraoptimal leaf temperatures. J. Amer. Soc. Hort. Sci. 119(2)243-248.
  2. Ranney, T. G. and R. E. Bir. 1994. Comparative flood tolerance of birch rootstocks. J. Amer. Soc. Hort. Sci. 119(1):43-48.
  3. Ranney, T. G. and E. P. Whitman, II. 1995. Growth and survival of 'Whitespire' Japanese birch grafted on rootstocks of five species of birch. HortScience 30:521-522.
  4. Ranney, T. G. and R. E. Bir. 1994. North Carolina urban tree evaluation program. Proc. SNA Res. Conf. 39: 347-348.

Return to Richard E. Bir homepage
North Carolina State University