Evil Flowers still provide an insanity Aura, even with Dark Petals I.

Dark Petals has the description "Evil Flowers hold no Fear for Wendy," however, even with the Dark Petals I skill equipped, Evil Flowers still have a sanity penalty and their insanity aura. This appears to be the case regardless of the skill was selected when first loading into the world, or during a play-through with the natural accumulation of insight.

This is specifically standing by naturally generated evil flowers, such as ones produced by totally normal trees or clockwork setpieces.