The great mullein thrives on open, sun-scorched areas, rocks, banks and barriers. First, it grows a rosette with large, light-coloured, wax-like leaves close to the ground. It gathers its strengths like this for one year, sometimes two. Then it grows an impressive stem the height of a person with a yellow blossom on top. The bloom produces up to 100,000 seeds that scatter around the plant. The seeds will keep in the ground for decades, maybe even centuries. If the habitat closes up or intergrows, the seeds remain in the ground in wait for better times. Turning the soil, digging a ditch or fortification work may provide it with room to grow.
In favourable conditions, the great mullein may grow year after year in one spot. The Pajamäki fortification rock is such a place.