Many perennials do not produce true from seed. Seed saved from garden phlox, for example, may produce plants with muddy pink flowers. Plants purchased from catalogs may arrive as small divisions or root cuttings. These have a better chance for survival if started in pots to be transplanted later. Perennials vary in size so when setting plants in the garden, be sure to space properly to allow ample room for growth.
Overcrowded plants are more subject to disease problems.
Do not leave plants sitting around after buying them. Plant them as soon as possible. Remove plants grown in containers with individual compartments for each plant by gently flexing the sides. Tear off the tops of peat pots, or bury completely at planting time. Any portion of a peat pot sticking out of the soil will act like a wick and dry out the rest of the pot.