Plants grown to cover over mine residues may die during cold winters during establishment years. In particular, the roots may decay because of a lack of oxygen in wet conditions. Festuca rubra sp. was directly seeded in gold mine residues and grown for four months after which they were transferred to larger pots. They were placed in an environmentally controlled chamber for vernalization during three months. Plants were then exposed to frozen conditions during another three months before thawing. A macropore was hand made to favor aeration in half of the pots. Roots and residues were submitted to computed tomography (CT) scanning before, during and after freezing. Relationships between root system parameters, macroporosity and residue properties will be discussed.