Resumo. Nutritional restriction and the occurrence of frost in southern Brazil often affects the growth of forest stands. In order to quantify the initial growth and resistance to frost of Toonna ciliata plants, in crops intercropped with Eucalyptus grandis in different fertilization, an experiment was conducted at UFSM, campus Frederico Westphalen, Brazil. The experimental design was a randomized block design with three replications, in factorial 2 x 2 x 3: two forest species (Eucalyptus grandis Hill ex Maiden and Toona ciliata M. Roem var. australis), two types of stands (single and intercropped) and three types of fertilizer (NPK, NPK + Si and NP slow-release + K + biostimulant). The growth of plant height was measured at different dates, up to 346 days after planting. At the end of this period, it was quantified the diameter at breast height and dry mass of shoots. The assesment of the level of damage to the plants and the degree of resistance to frost was with grading based on the entire plant and tree canopy. The data were submitted to variance analysis and when significant (p ≤ 0.05), we proceeded to compare the treatment by means of Tukey test (p ≤ 0.05). The two forest species were tolerant to frost, but with greater damage to the leaf area in plants Toona ciliata against the Eucalyptus grandis. The cultivation Toona ciliata under protection the Eucalyptus grandis has not diminished the damage to frost in the first year of field deployment. The use of slow-release fertilizer, Si and biostimulant did not contribute to increasing growth and resistance to frost the plants of the two forest species.