It was shown through the example of two-year-old seedlings of Betula pendula Roth and B. pubescence Ehrh that silver birch and downy birch differ from one another in the strategy of metabolites distribution already at early ontogenetic stages. In B. pubescence, more metabolites are retained in the crown during active cambial growth. Trunk tissues are powerful attracting centers for photoassimilates in both silver birch forms. A high metabolic status is the background for the formation of the conducting system. An accumulation of carbohydrates in B. pendula var pendula results in the formation of thick-walled xylem vessels with strong lignified cellular walls. An intensive accumulation of sucrose in B. pendula var. carelica takes place in the phloem. Supposedly, an increase in sugar content in the phloem of Karelian birch in the period of active cambial growth can disrupt the cambial activity, resulting in the formation of structural anomalies of wood.