For May and June I had to do a shortlist to keep it short. Most notable was the finding of unusual forms of green Trilliums, as well as many pink forms. The reddish flower in the pictures is a fading pink form (T. grandiflorum fo. roseum Farwell).
And not just the colour variation was remarkable but also the variation in petals shape and size! A form with particularly narrow, long pointed petals attracted my attention, as did a truly gigantesque white specimen.
A most beautiful form of Hepatica americana with extra petals also made the shortlist:
From the cultivated plants: the first flower of Gentiana clusii var. rochelii, seen above in the featured image, and the flowering of the neglected Dactylorhiza alpestris, from my Little plants series.