In vitro polyploidy induction offers the possibility of quick multiplication over in vivo methods, and is therefore particularly interesting for slowly growing plants. Three different in vitro protocols for the induction of tetraploid Rhododendron simsii hybrids were evaluated. The most successful technique was a daily application of mitotic poison on the apical meristem of seedlings. However, this technique was quite labour intensive.Direct sowing on media enriched with antimitotic agents requires less work but is less efficient. To induce ploidy chimeras starting from an existing genotype, mitotic inhibitors
can be added to multiplication media