I was almost home from today’s 7-mile walk when I spotted the subject of this post, lots of pink gall-like bumps on the leaves of a group of plants I quickly realised were Nipplewort (Lapsana communis).
And that clinched the identification of the bumps, especially when I turned a leaf over and spotted the little yellow dots. These are the aecia, cup-shaped structures in which aeciospores are produced. (And, as you can see, this particular leaf was also home to a tiny spider.)
These Nipplewort plants were absolutely covered in rust fungi, Nipplewort Rust (Puccinia lapsanae), a rust I’ve seen before but never in such quantity.