Perennial plants live in the same place for many years, so it's important to start them out in good soil.
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Tammy Algood of the University of Tennessee Agricultural Extension Service offers tips for planting and caring for garden perennials.
Scabiosa and coreopsis are sun-loving perennials that thrive in hot summer sun. Scabiosa will tolerate some shade and still bloom profusely. Coreopsis will bloom throughout the summer and fall if regularly deadheaded. Both do well in Zone 4 through 10.
Before planting perennials, most gardeners will need to amend the soil to improve its texture and drainage. Perennial plants live in the same place for many years, so it's important to start them out in good soil. Tammy advises digging generous holes so you can amend topsoil as well as the subsoil. Dig down at least 12" to 18", and transfer the soil from the hole to a wheelbarrow. Remove any rocks or debris. Add perlite and vermiculite to improve the soil's drainage. Dump the amended soil into the planting hole.
After you've finished planting, set up soaker hoses to surround the plants. Soaker hoses deliver water near plants' roots, and very little is wasted due to evaporation.
Various fittings are available to customize soaker hoses to conform to any garden situation, and it's easy to fit the parts together.
Once the irrigation system is in place, mulch the soil to slow weed growth and moisture loss and to protect the hoses.