Clump forming perennials fill in areas of the flower garden like little bushes. The main propagation method for perennial clumps is department. This produces clones of the parent plants, as it is an asexual way of propagation. Clumping perennials develop an extensive root system and dividing the clump each two to three years from the first spring prevents problems created by overcrowding.
“Small Lanterns” columbine (Aquilegia canadensis “Small Lanterns”) blossoms in spring with red and yellow lantern-shaped blossoms that attract hummingbirds and butterflies to the garden. This herbaceous perennial grows best in U.S. Department of Agriculture plant hardiness zones 3 through 8, reaching 9 to 12 inches tall and broad in full to part sun. Pink pussy-toes (Antennaria dioica “Rubra”) form low-growing clumps, 4 to 6 inches tall and spreading 10 to 12 inches wide using miniature silver-gray leaves and fuzzy pink flowers appearing in late spring. This North American native grows as a ground cover in USDA zones 1 through 9.
“Red Butterflies” milkweed (Asclepias curassavica “Red Butterflies”) rises well in USDA plant hardiness zones 8 through 11, with clusters of red and yellow blooms on upright stems reaching 36 inches tall. This sun-loving border perennial attracts monarch butterflies to the lawn. “Serenade” Japanese anemone (Anemone x hybrida “Serenade”) creates double pink petals surrounding yellow centers around 24-inch-tall stems during late summer in USDA zones 4 through 8. The dark green leaves form clumps 12 inches tall, spreading 24 inches broad, in moist soil, part sun locations.
Mammoth “Dark Bronze” garden mum (Chrysanthemum morifolium “Dark Bronze”) creates orange-bronze petals surrounding yellow centers with dense clumps of leaves 14 inches tall and 20 inches wide during the year. This herb perennial matures to 3 feet tall and 6 feet wide in USDA zones 3 through 9, in full sun exposure. Pink Elf saxifrage (Saxifraga fortunei Pink Elf) grows best in USDA zones 7 through 9 in full to partial shade. The 6- to 10-inch-high clump disperses 8 to 12 inches wide, composed of bronze-tinted leaves using reddish-purple undersides. Sprays of pink flowers appear from late autumn through early winter.
“French Hybrid” bush lily (Clivia miniata “French Hybrid”) stays evergreen in USDA zones 9 through 11. Large green strap-like leaves and orange blossoms cluster in addition to tall flower stems, reaching 18 to 30 inches tall from the winter through spring. “Night Coaster” Lenten rose (Helleborus “Night Coaster”) rises in in USDA zones 4 through 9, creating 3-inch-wide blackish-purple bowl-shaped winter blossoms, 18 to 22 inches tall. Leathery dark green glossy leaves forms 24-inch-wide clumps in moist soil located in shady growing states.