Epilobium angustifolium

The plant is 50 to 150 cm tall, upright, usually unbranched and hairless.

The pink to purple flowers stand in a long terminal raceme, with petals up to 15 mm long.

Info Flora gives the flowering period of fireweed in Switzerland as June to August.

The Czech Pladias database records fireweed as insect pollinated with selfing, flowering June to September in Czechia.

Fireweed is protandrous: each flower passes through a male phase before a female phase, as a Canadian study of its pollen schedules notes.

In Switzerland it grows in open forest sites, rock debris and on banks, from the colline to the subalpine and sometimes alpine belt.

A University of Bayreuth species sheet lists its habitats as clear cuts, forest clearings, tall herb communities and forest tracks.

In a Polish study the nectar sugar concentration stayed constant through anthesis at 47 percent on average.

The same study found that female phase flowers produced on average 1.4 times more nectar than male phase flowers, and the nectar shifted from sucrose rich to hexose rich.

Near Wuerzburg, Germany, fireweed flowers produced on average 2332 micrograms of sugar in 24 hours and were visited by Bombus terrestris workers.

The Bavarian forest institute LWF says fireweed is common on forest clearings and is an important nectar and pollen source in late summer.

The Bavarian forest institute LWF advises that smaller forest gaps should sometimes be left to themselves, so that plants such as fireweed can establish.