Perennial Plant Maintenance
Iris should be planted in July, August or September, so that the roots of newly planted Iris are well established before the growing season ends. Iris are also available as potted plants in the perennial lot and can be planted in spring, summer or fall.
Iris will thrive in well-drained garden soil. Plant on a slope or in raised beds to ensure good drainage. If your soil is heavy, add coarse sand to further improve drainage. Gypsum is an excellent soil conditioner that can improve most clay soils. The ideal pH is 6.8 (slightly acidic), but Iris are tolerant in this regard. To lower the pH of your soil, you may add sulphur to alkaline soils.
Where to plant
Iris need at least a half day of sun. In extremely hot climates some shade is beneficial, but in most climates Iris do best in full sun. Be sure to provide your Iris with good drainage. Plant either on a slope or in raised beds.
Depth to plant
Plant Iris with the tops of the rhizomes exposed and the roots spread out facing downward in the soil. In very light soils or in extremely hot climates, cover the rhizome with 1 inch of soil. Firm the soil around each rhizome and then water to help it settle. A common mistake is to plant Iris too deeply.
Iris are generally planted 12 to 24 inches apart. Close planting gives an immediate effect, but closely planted Iris will need to be thinned often. Plants spaced further apart will need less frequent thinning.
Plant Iris from 12 to 24 inches apart. If you chose to plant closer together for immediate effect, you will find that they need to be thinned more often.