Arabis Snow Cap (rock Cress) Seeds have masses of tiny, snow-white fragrant flowers that appear in early spring starting April through May/June against a backdrop of evergreen foliage. The silvery-green foliage is 15-20 cm tall. Foilage provides an excellent ground cover all season long. Thin plants to 15 cm apart when transplanting or thinning out seedlings. To keep plant compact shear down all foliage after flowering.