Culture
Best grown in humus-rich, evenly moist, well-drained soils in full sun. Grows well in sandy soils. Intolerant of wet, heavy soils. Plants require sharp soil drainage, particularly in winter when root rot can be a severe problem. Best with a full sun exposure, but tolerates some light shade in hot summer climates. To the extent possible, locate in areas protected from wind. Promptly remove spent flower spikes. Crowns benefit from winter protection in USDA Zones 5 and 6. Tie leaves together in late fall to form a canopy over the crown in order to prevent water from settling in the crown and freezing. Root mulch in winter is also advisable. Cut back foliage to 3” above the ground in early spring in anticipation of the new growing season. Established clumps are best left undisturbed. If division becomes needed because of overcrowding, consider severing offsets from the edge of the plant to minimize the amount of disturbance to the rhizomes. Species plants may be grown from seed. Named cultivars usually must be divided, however, because the flower color typically will not come true from seed or viable seed will not be produced.
‘Cobra’ will not come true from seed.
Noteworthy Characteristics
Kniphofia is a genus of 60-70 species of evergreen to deciduous, mostly clump-forming, rhizomatous perennials featuring linear strap-shaped basal leaves and showy bottlebrush-like flower spikes. Common names such as red hot poker, rocket flower and torch lily describe the showy flower spikes (often broad at the top but tapered at the base) which are the sine qua non of this ornamental perennial. Species plants are native to mountainous areas in southern to tropical Africa. From the center of a basal tuft (rosette) of coarse, strap-shaped, linear leaves rises a succession of thick, naked flower scapes featuring dense, terminal, spike-like racemes of drooping, short-stalked, tubular flowers. Flowers in each scape typically bloom, bottom to top, from late spring to mid-summer, often with some continued bloom to late summer or early fall. Numerous flower colors are available in commerce, including shades of red, orange, pink, yellow, white, greenish-white, creamy pastels and bicolor. Plant size ranges from dwarf (to 1 1/2’ tall) to very tall (to 6’ tall).
Hybrids are common and have considerably extended the available color options, plant sizes and bloom times. Hybrid development dates back to the mid-19th century when Kniphofia uvaria was crossed with several other species now currently known as K. bruceae, K. galpinii, K. pauciflora and K. triangularis. Most of the garden plants grown today are hybrids between 2 or more species.
Genus name honors Johann Hieronymus Kniphof (1704-1763) German physician and botanist.
‘Cobra’ is a hybrid kniphofia that produces ornamentally impressive copper-orange flowers which fade to creamy yellow and finally to creamy white. Flowers appear in upright terminal racemes to 6-10” long atop naked flower spikes rising to 3 1/2’ tall. Strap-shaped medium green leaves form a basal clump to 2 1/2’ tall and as wide. Flower spikes typically bloom, in succession, over a long late spring to early fall bloom period, with the bloom on each flower spike lasting about eighteen days. Each flowering spike tapers at the base, thus somewhat resembling a torch or poker.
Problems
No significant insect or disease problems. Root rot may occur in wet, poorly-drained soils. Thrips may appear in some areas.
Uses
Outstanding vertical accent. Effective specimen. Small groups in a perennial border.