Most varieties of Japanese iris are best planted in the spring, after all threat of frost has passed. Irises like to become established in their first year, so planting at springtime gives your irises plenty of time to put down roots before the winter. If you order Japanese Iris from Michigan Bulb, we'll send them at just the right time to plant! If you're unable to plant quickly, you can store the iris rhizomes in a cool, dry area until you're able to get them into the ground.