Perennial trailing flower plants come back year after year and need sufficient space to spread out as they mature, planting these types of plants in containers frees up space for smaller plants in the garden. Perennial trailing flower plants offer a beautiful addition to your garden and available in a wide array of options from which to choose. Perennial trailing flower plants also need a large amount of space in the garden to spread out their roots. Pruning of perennial trailing flower plants occurs in the late fall or early spring to promote new growth come springtime. Container-grown perennial trailing flower plants require mulching and proper air flow. Mulch ensures the retention of moisture, while holes in the bottom of the container prevent root rot.