Iris giganticaerulea, the giant blue iris, is a species of iris, in the subgenus Limniris, in the series Hexagonae. It is a rhizomatous perennial, from northern America. It has long bright green leaves, very tall stems and one or two musky fragrant flowers in a range of blue shades (pale, bright, dark, lavender and violet) or rarely white. Description Iris giganticaerulea (the giant blue iris) is the largest species of the Louisiana irises. It has very large green rhizomes, which are between 5 and 12 inches (13 – 30 cm) long and 0.75 to 1.5 inches (2–4 cm) thick. They are shallow rooted, marked with the scars (of the previous seasons) leaves, with many branches, which can form a large clump/colony growing up to 6 x 3 feet (182 x 91 cm). Rising from the plant's base are four to six bright green leaves, ensiform (sword-shaped) and between 20 and 30 inches (50–76 cm) long, 1.5 inches (4 cm) wide. It has very tall stems, that can grow between to between 28 – 71 inches (70–180 cm) tall. They have two or three branches, with one or two terminal flowers rising above the leaves. There may be up to twelve flowers on the plant. It blooms from early to mid spring, in the UK and America, with musky flowers. It comes in a range of blue shades, from pale blue, to lavender blue, to bright blue, to dark blue, and to violet blue. Occasionally there is a white form, or yellowish white. The flowers are generally 5 to 6 inches (13 to 15 cm) across. They have six petals, three outer sepals (called the falls), which are flaring (1.75 inch or 4 cm wide), arch downward and have a white or yellow or faint orange signal patch or ridge. They also have three inner sepals (called the standards), which are slightly erect or upright and narrower than the falls. It has a 4–5 cm long perianth tube, blue-violet style 1.3–1.5 inch (3.5–4 cm long) and two-lobed stigmae. After flowering, it has bright green ellipsoid capsules 3–4 inches (7–10 cm) long by 1 inch (3 cm) wide, which are hexagonal in cross section and shaped like a D. Genetics As most irises are diploid, they have two sets of chromosomes. This fact can be used to identify hybrids and classification of groupings. It has a chromosome count of 2n=44. It has