How to Take Care of Your Irises

 

When to Plant

For best results, Iris should be planted in July, August or September. It's imperative that the roots of newly planted Iris be well-established before the growing season ends. In areas with hot summers and mild winters, September or October planting may be preferred. Check the Zone Map to determine if your item will be "Winter Hardy" when ordering. 

 

Where to Plant

Iris’ need at least a half day of sunlight. In extremely hot climates, some shade is beneficial, but in most climates Iris do best in full sun. Be sure to provide your Iris good drainage, planting either on a slope or in raised beds.

Soil Preparation

 

Iris will thrive in most well-drained garden soils. Planting on a slope or in raised beds helps ensure good drainage. If your soil is heavy, coarse sand or humus may be added to 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 adjust the pH of your soil, lime may be added to acidic soils or sulfur to alkaline soils. It is always best to have your soil analyzed before taking corrective measures.

 

Depth to Plant

Iris should be planted so the tops of the rhizomes are exposed and the roots are spread out facing downward in the soil. In very light soils or in extremely hot climates, covering the rhizome with 1 inch of soil may be desirable. Firm the soil around each rhizome and then water to help settle the soil. A common mistake is to plant Iris too deeply.

 

Distance Apart

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.

 

Watering

Newly set plants need moisture to help their root systems become established. Specific

watering information depends on your climate and your soil, but keep in mind that deep

watering at long intervals is better than more frequent shallow watering. Once established,

Iris normally doesn’t need to be watered except in arid areas. Over watering is a common

error.

 

Fertilization

Specific fertilizer recommendations depend on your soil type, but bone meal, super

phosphate and 6-10-10 are all effective. A light application in the early spring and a second

light application about a month after bloom will reward you with good growth and bloom.

Avoid using anything high in nitrogen, as nitrogen encourages rot problems.

 

Thinning Old Clumps

Iris’ need to be thinned or divided, before they become overcrowded. Generally every 3-4

years is suffient. If Iris’ are allowed to become too crowded the bloom will suffer, some

varieties may crowd others out and disease problems may be aggravated. Old clumps may be

thinned by removing the old divisions at the centers of the clumps and leaving new growth in

the ground. Or, you may dig up the entire clump and remove and replant the large new

rhizomes.