Portuguese squill, also known as Giant squill, Peruvian jacinth

Portuguese squill boasts dark green, strap-shaped leaves that form a rosette up to 18 inches (45 cm) wide. In the heart of spring, 6 to 12 inches (15 to 30 cm) tall stalks rise from the center, topped with densely packed heads of deep blue flowers. The bloom lasts for several weeks. It thrives with good drainage and lean soil, and can tolerate a range of watering regimes. This plant can endure temperatures as low as 5° F (-15° C). It should be noted that portuguese squill contains toxic glycosides.