It is intended to provide a flower color crossing method whereby a
specific flower color is passed to the next generation of delphinium and
a flower color crossing method whereby a dichromatic flower color is
passed to the next generation of delphinium. It is also intended to
provide a method whereby perpetual delphinium can be efficiently obtained
in a warm place and a method of determining a delphinium flower color
based on the ratio of main inherent colorants in the sepal. It is found
out that a specific flower color can be passed to the next generation by
using a full-color delphinium as a pollen parent or a seed parent and
carrying out allogamous crossing and, at the same time, a dichromatic
flower color can be passed to the next generation thereby. By growing a
delphinium seedling under such conditions as allowing its germination in
a petri dish at a temperature of about 15.degree. C., a method of
efficiently obtaining perpetual delphinium in a warm place is found out.
By analyzing delphinium flower colors and inherent colorants, a numerical
formula for determining a delphinium flower color is established. A
crossing method for obtaining purple or pale purple delphinium flowers
containing novel anthocyanin as the main component is found out. Also, a
method of isolating and purifying the novel anthocyanin colorant is found
out.