Modern studies emphasize the extraordinary importance of silicon nutrition of plants in the formation of plant resistance to biotic and abiotic stress. The aim of the research is to evaluate mineral nutrition and detox effect from Si-K foliar top-dressing, which was tested for urban plants Aésculus hippocástanum L. and Tilia cordata Mill. The paper contains data describing that foliar top-dressing with Si-K concentrate causes better detox effect from Pb and Cd. In Aésculus hippocástanum foliage: Pb concentration was 14 times reduced and Cd concentration was 2 times reduced. In Tilia cordata foliage the Cd concentration was 2 times reduced and Pb concentration was 1.9 times reduced. In Tilia cordata flowers the Cd concentration was 2.5 times reduced. It was noted increasing in biogenic elements: zinc in Aésculus hippocástanum foliage, copper – in Tilia cordata foliage. It’s can be explained by the genetically determined needs of these plants and the ability of silicon to contribute to meeting these needs.