Daylilies

The daylilies are in the genus Hemerocallis which is within the lily family. Compare their flowers to those of common garden lilies, and the similarities should become evident. So many different species of daylilies have been incorporated into our modern hybrids that the botanical name (H. x hybridus) reflects this fact. The "x" denotes hybridization, and the word "hybridus" emphasizes this. Today, we can purchase single and double flower forms, yet all daylily flowers routinely last a single day, as the name implies. Flower quality has been altered greatly by the development of tetraploid daylilies (i.e., those with twice the normal number of chromosomes). Such cultivars have larger, heavier-substance flowers that may feel waxy. Tetraploids are indeed striking, but may be slower growing and possess fewer flowers per plant than the diploids (daylilies with a normal chromosome number). Some tetraploid species are 'Charles Johnston,' a cherry-red cultivar; 'Decatur Apricot,' a coral-pink cultivar with a gold throat; and 'Sky Kissed,' with bright, lavender-purple flowers.

Two very specific trends in daylily breeding have resulted in some exciting breakthroughs. First, the "Altissima" types were derived from a Japanese species of the same name. They are noticeably distinct, often sending up a flower stalk 6 to 8 feet high. Foliage, on the other hand, is hardly unusual and grows to 2 feet. Everyone will have particular thoughts on how to use this peculiar strain of daylilies. They are excellent companions to the taller ornamental grasses. Most Altissimas flower later in the summer, typically from mid-July to September, and height alone generally qualifies the Altissima for background placement in any perennial border. Obtaining them may be frustrating because local retailers usually stock the more common cultivars; however, mail order sources carry them. The second breeding trend, the development of so-called "everblooming" daylilies, is nothing short of a minor phenomenon for residential and commercial landscapes.

The cultivar 'Stella D'Oro' has become an incredibly popular choice in this regard. Its flowers are golden-yellow, with ruffled edges. Other selections exist, but their resemblance to 'Stella D'Oro' is strong; no surprise since "Stella" is used in everblooming breeding programs. Examples of this are 'Song Sparrow,' 'Happy Returns,' and 'Mini Stella.' It is debatable whether everblooming and "reblooming" are synonymous with respect to daylilies. The former may be typified by a non-stop appearance of flowers up to frost. By contrast, rebloomers tend to flower, stop for a period, then resume flowering at a later date. A great many daylilies just behave like most herbaceous perennials and flower for several weeks during early, mid-, or late summer.

Daylilies form thick, tuberous roots that grow rapidly to form dense clumps. We consider many cultivars to be excellent ground covers because they successfully compete with invasive weeds. Spreading, however, is not by underground stolons (stems) like a pachysandra. Instead, individual daylilies become large clumps with multiple growing points. While fall is the best time to divide and transplant tuberous root clumps, they are sufficiently resilient to be moved any time with few setbacks or detrimental consequences. Occasional clump division is not essential, but may revitalize flowering of some cultivars. Daylilies have actually been used as mass plantings for highway exit ramps in Asheville, North Carolina!

Gardeners always have considered daylilies to be the ultimate species for pest resistance and, relatively speaking, they probably still are. Unfortunately, there is a significant fungal disease in Virginia that attacks daylilies specifically. The culprit, Collecephalus hemerocalli, causes length-wise yellow striping accompanied by irregular brown spots on the foliage. You also may notice a decline in flower production. This fungus is most damaging in early spring. It should be treated promptly according to label directions with a commercially available fungicide. Mid-summer occurrences of daylily leaf streak disease are rare since the fungal organism suffers at temperatures above 90F. Some cultivars are more susceptible than others, so don't be surprised if the disease occurs selectively or not at all on your plants. Daylilies should be grown in spite of the leaf streak problem. Their garden performance is still most rewarding! New cultivars are released regularly, but availability often is limited. Your best chance of obtaining something really new, soon after introduction, is via mail order catalogs and local breeders. Good friends and garden-related magazines will point you in the right direction.