This cloud of white flowers is Snow on the Mountain, Euphorbia leucocephala.

For most of the year, it is an attractive green shrub or small tree. But when it blooms, usually during the shorter days of the year, the branch tips become covered with white floral bracts, creating the appearance of freshly fallen snow.

The true flowers are actually very small. The showy white structures surrounding them are modified leaves called bracts, similar to those of its better-known relative, the poinsettia.

The flowers attract bees, butterflies, and other insects. After flowering, small three-part seed capsules develop among the fading bracts.

Snow on the Mountain is native to Mexico and Central America but is widely grown in tropical gardens. It responds well to pruning and may be maintained as a rounded shrub, hedge, or small tree.

Like other members of the Euphorbia genus, it produces a milky latex when cut. This sap can irritate the skin and eyes, so the plant should be handled with care.

Its flowering period is relatively brief, but while it lasts, Snow on the Mountain can look as though an entire tropical shrub has been dusted with snow.