Spacing of Iris Bulbs

Outdoor Spacing

• Bearded irises are a variety that generally requires spacing at least 8 inches apart and up to 1 or 2 feet apart for large varieties. Gardeners should space Dutch iris bulbs 4 to 6 inches apart, as the University of Illinois Extension and North Carolina State University suggest. In general, dwarf varieties require less space than larger varieties.

Indoor Spacing

• Gardeners can force spring bulbs to bloom during different seasons by planting them in pots indoors and simulating their outdoor winter chilling period followed by warm spring conditions. According to the University of Rhode Island, gardeners can plant forced bulbs very close together without considering their spacing.

Considerations

• Large varieties of irises, like many types of Siberian irises, require more space than dwarf varieties. Gardeners can plant bulbs close together initially, but may have to thin them out or dig some up and split them in two from time to time.