There are several species of Cerastium but very few are generally available. The only one I have found and used is C. tomentosum. Although native to Sicily and Italy but hardy to zone 2, it is a great perennial for Ohio gardens, particularly as a silvery groundcover. It is evergreen (evergray) to semi-evergreen depending on the  winter weather.

In May, this perennial is covered with small white flowers, thus the common name of Snow-in-Summer. It should actually be called Snow-in-Late -Spring. Because the woolly foliage only grows six inches high, I use it as an edging or front of the border plant. It would also be perfect in rock gardens or dry laid stone walls with planting pockets. The white flowers are held on eight to twelve inch high stems and have five to ten petals. Each stem can have multiple flowers. While the species grows quite rampantly, the cultivar ‘Yoyo’ is more compact. I have no idea why the cultivar was named ‘Yoyo’ because it does not bounce.

The key to success with Cerastium is full sun and very well drained soil (add lots of enlarged aggregate if your soil is clay). Thus, it is an excellent candidate for xeriscapes. Happily, this low maintenance perennial is deer resistant and probably also rabbit resistant.

I’m guessing that if you install this perennial in April, it will be blooming for you in May.