It is very important to start with good ground preparation. If starting a new bed in your yard remove all annual and perennial grasses and weeds. Once the plant material has been killed, turn the ground with a rototiller or shovel. Work your soil well to depth of 10 to 12 inches
Bearded Iris like well drained loamy soils. Add humus such as well rotted grass clippings, manure or ground leaves to sandy and clay soils to help keep the ground workable. Gypsum is an excellent soil conditioner for most clay soils. Adding peat moss will hold moisture too long for bearded iris and help contribute to rot problems. If possible use raised beds to help improve drainage.
It is a good idea to get a soil test from your county extension agent before applying any unnecessary fertilizers to newly prepared beds. Spots that have never grown iris before usually have enough nutrients in the soil to sustain new rhizomes. Soil pH should be neutral between 6.8 and 7.0, but can range anywhere between 6.1 and 7.2. The symbol pH expresses the relative acidity or alkalinity of the soil. To correct soil that is too acidic, apply hydrated lime. Apply a product containing sulfur to improve alkaline soils.
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