Bulb cultures of Leucojum aestivum and L. aestivum ‘Gravety Giant’ were subcultured in medium containing the precursor 4’‐O‐methylnorbelladine (MN) at various concentrations [0 (control), 0.15 and 0.3 g/L]. The cultures were conducted in bioreactor RITA® and lasted for 15, 30, 40 and 50 days. The growth rate and the alkaloid accumulation in bulblets were studied. For this latter purpose, a purification method was developed. It comprised a highly selective solid phase extraction using on the one hand, UPTI‐CLEAN SI and SCX cartridges for plant extracts and on the other hand, 2H cartridges for culture media. Pure alkaloidal fractions were, thus, analyzed by LC‐ESI‐MS allowing the quantitative evaluation of galanthamine and lycorine from culture extracts. Precursor feeding along with temporary immersion conditions was found to significantly improve the accumulation of both galanthamine and lycorine. The maximal concentrations of galanthamine (0.81 mg/g DW) and lycorine (0.54 mg/g DW) in L. aestivum bulblets were reached, respectively, after 40 days of culture with 0.15 g/L of precursor and after 30 days of culture with 0.3 g/L of precursor. In L. aestivum ‘Gravety Giant’ bulb cultures, 0.3 g/L of precursor was the best condition for both galanthamine (0.6 mg/g DW after 50 days) and lycorine (1.13 mg/g DW after 30 days).