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Yellow Flag Yellow flag is a European bog flower naturalized to North America.

Yellow flag belongs to the genus Iris, which is a particularly vast one. It includes the common bearded iris of the flower garden, rock garden irises, bulbous irises, and marsh irises. Of the many bog-type irises, none is as striking and popular as the yellow flag. Although a European native, it is widely naturalized in North America.

Description of yellow flag: This is a tall-growing plant with sword-shaped leaves. Its leaves alone can reach 4 to 5 feet, and the flower stalks are often a foot or so taller. The blooms are bright golden yellow and appear in late spring and early summer. Variegated varieties also exist. Ease of care of yellow flag: Easy.

Growing yellow flag: Plant in full sun in either boggy soil or in containers set into the pool. The roots can be covered by a few inches of water to more than a foot. It prefers a slightly acid soil. Remove faded flowers to prevent seed formation.

Propagating yellow flag: The yellow flag spreads rapidly by rhizomes and is easily reproduced by division. It can also be grown from seed.

Uses for yellow flag: Bog or emergent plant. Excellent background plant for larger water gardens.

Related species of yellow flag: The blue flag (Iris versicolor) is basically a blue-flowered version of the yellow flag, although a bit shorter (about 2 feet). Other irises for boggy places include the Japanese iris (I. ensata, formerly I. kaempferi) and the Siberian iris (I. sibirica), both of which are covered more thoroughly in the "Perennials" section. All the above are hardy to zone 4.

Scientific name of yellow flag: Iris Pseudocorus

NOTE: This plant is considered invasive in much of North America.

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