Ox-eye daisy.

My very first photograph using a DSLR (Nikon D90 with the 18-105mm lens). Processed with Nikon Capture NX2.

Leucanthemum vulgare, the ox-eye daisy (syn. Chrysanthemum leucanthemum), is a widespread flowering plant native to Europe and the temperate regions of Asia and an introduced plant to North America, Australia and New Zealand. It is one of a number of Asteraceae family plants to be called a "daisy" and has the vernacular names: common daisy, dog daisy, moon daisy, and oxe-eye daisy.
Leucanthemum vulgare is a typical grassland perennial wildflower, growing in a variety of plant communities including meadows and fields, under scrub and open-canopy forests and in disturbed areas. Leucanthemum is from the Ancient Greek λευκός ("white") and ἄνθεμον ("flower").
(Wikipedia)