A Joshua Tree propagates both by pollination and
by sending out long underground roots and sprouting new plants from
those roots. In general pollination is better because they can spread
over larger areas. The trees rely on the a specialized moth for
pollination and no other insect or bird transfers the pollen from one
flower to another. Without the moth's pollination, the Joshua Tree
could not reproduce, nor could the moth, whose larvae eat the Joshua
Tree seed. The white or greenish flowers can appear from March to May,
but they require just the right combination of temperature and moisture,
and several years may pass without a major blooming.
