These are wild flowers that spring up in the yard every year. These will be out for a week or so, then some of the new varieties will show up. These were taken in my yard just to show you as they are now blooming. Some didn't come out due to poor photographic skills and a bright sun that washed out the view screen so I could not tell exactly what I was imaging.
(http://s017.radikal.ru/i403/1603/47/1f34ac126955.png)
(http://s13.radikal.ru/i186/1603/dd/63d134f09e4f.png)
(http://s019.radikal.ru/i610/1603/de/41fe663291d0.png)
(http://s46.radikal.ru/i111/1603/77/a5f0ae415069.png)
(http://i053.radikal.ru/1603/8b/4eccbd6a0c9e.png)
A little later in the season, the purple ones you see in the last image will be everywhere. When you look at it from a long distance angle you won't see grass, you'll see a purple ground cover.
I mowed my grass last week. That's how fast this stuff grows.