The experiment was carried out at the Department of Ornamental Plants in the Agricultural University in Lublin in the years 2000–2002. The plant material was corms of Acidanthera bicolor var. murielae Perry with a circumference of 8–9 cm, which in number of thirty was planted on a plot 1.2 m², at 8 cm of depth in the second week of May. According to the scheme of experiment: linuron 1.000 kgּha^-1, pendimethalin 0.990 kgּha^-1 and napropamide 1.500 kgּha^-1 were applied one week after planting the corms of the research plant. Next day some plots were mulched with 5 cm thick layer of pine bark or peat. The experiment included also a control set without herbicides and mulches, which it was hand weeded and a control set with delay hand weed performed three week late compared with the rest plots. At the end of vegetative stage the measurement was carried out on 10 plants of each plot including: length of flower stem, number of flowers and length of spike. It was noted that linuron, pendimethalin and napropamide did not injury to plants of Acidanthera bicolor. Application of linuron and pendimethalin beneficially influenced on number of flowers (respectively by 9.65 and 9.72 piecesּplant^-1), length of flower stem (respectively by 102.54 and 101.52 cm) and length of spike (respectively by 40.14 and 40.28 cm). Besides application of napropamide had a positive effect on received of greater number of flowers (9.40 piecesּplant^-1) and longer spike (39.60 cm). Delay of hand weed about three weeks had a negative effect on yield and quality of flowers of the research plant which formed the smaller number of flowers and the shortest flower stems and spikes (respectively by 8.4 piecesּplant^-1, 96.2 cm and 35.4 cm). It was received the longer flower stems in combinations where applied of pine bark or peat as a mulch (respectively by 100.88 and 100.23 cm) in comparison with combination without mulch (97.96 cm). There was no noted considerably influence of organic mulches on number of flowers in spike and length of inflorescence.

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