Salix (willow) includes over 300 species, found mostly in
the arctic to temperate northern hemisphere. None of the Salicaceae
are native to Australia. The leaves are generally simple, alternate
and narrow. The female and male flowers are on different stems.
The seeds are small (< 2 mm) with a white tuft (coma). They only
germinate in saturated soil, but willows proliferate asexually through
underground stems. The plant form ranges from dwarf shrubs (tundra)
to tall (20 m) streamside trees.
Pollen light micrograph:
Generally small, 20 - 25 µm, prolate, reticulate pollen grains,
with a pronounced margo. The reticulation (both muri and lumina)
decreases in size near the furrow, often producing a psilate margo
parallel to the furrow. The muri of the reticulation varies from very
sharp to broadly rounded, and the lumina generally decrease in size at
Pollen scanning electron micrograph (SEM)
The APMRU micrograph clearly displays the distinctive margo,
and the football (rugby!) shape of the willow grain.
Production and Dispersal:
Willows are both wind and insect pollinated, even within single
species. Their pollen production and dispersal are moderate.