In many ornamental plant species the light spectrum can, to a varied extent, modify growth and flowering. The literature offers information on the inhibition of growth of seedlings and cuttings of ornamental plants exposed to blue light. In this paper was investigated the effect of light of a varied spectral composition on the growth of scarlet sage (Salvia splendens) seedling. The plants were cultivated in the growth chamber at the 16-hour and 20-hour day. The following kinds of light were used: daylight – similar in its spectral composition to natural light, blue and mixed light – with the same share of daylight and blue light as well as with 75% share of blue light. The intensity of the quantum irradiance in the range PAR was the same for all the experiment combinations and it was 110 μmol · m^-2 · s^-1. The scarlet sage grown in mixed light with the advantage of blue light was lower than the plants produced in daylight both at the 16-hour and 20-hour day.

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