Planting Perennial Beauty
Container grown perennials can be added to the garden anytime of the season. Avoid mid summer if you don't want the extra work of keeping the soil moist and plants healthy during the extreme heat.
Properly prepare the soil before placing plants in the ground. This is especially important since the goal is to have these plants growing in the same area for several, hopefully many seasons.
Gently squeeze or roll the pot to loosen the roots. Tip and slide don't pull the plant out of the container. Loosen or slice through any circling roots to encourage root development beyond the original rootball.
Set the plant in a hole the same depth and at least twice as wide as the rootball. Fill with soil and gently tamp.
Add a bit of low nitrogen, slow release fertilizer if you mulch with wood chips. This replenishes the nitrogen temporarily tied up by the wood mulch. Water thoroughly and often enough to keep the roots and surrounding soil moist.
A bit more information: Keep perennials looking good all season. Remove diseased leaves and damaging insects as soon as they are found. Removing faded flowers on many perennials encourages a second or third flush of bloom. Allow the final flush of flowers to set seed. The seed heads add beauty to the winter landscape and provide food for the birds.