The paper presents mathematical model of stalk elastic strain. The author executed the calculations of elastic strain for single stalk and layer of stalks. The plant stalk cross-section was treated as a thin-walled slightly curved ring. On the ring the concentrated force was applied. That force imitated action of a blade. The calculation of strain vs. force was based on Castigliano theorem. There were presented two cases of static cutting according to energetic methods of elastic strain calculating. One of them presents elastic behavior of the single stalk under concentrated load and the second one behavior of the layer of stalks. In both cases there were calculated deflections of the rings. After favorable empiric verification, the results of the calculation may be useful in the analysis of stalk material cutting effects.