Double Daylilies

Double daylilies are a passion for many gardeners and hybridizers. The extra petals and petaloids add a greater sense of fullness and depth to the flower, creating a beauty that has captured the imagination and hearts of flower lovers and breeders. Like double flowers of other genera, such large, full flower form adds a new dimension and gives a completely new look to the flower.

Double daylilies are by no means a new flower form. Plants of the Hemerocallis species found growing wild in China included H. fulva var. kwanso and H. fulva 'Flore Pleno', both doubles. Unfortunately, these flowers are triploids, which are sterile, and could not be used in creating modern hybrids.

The hybrid double daylily was created from single daylilies that sometimes had double tissue. These doubles, often only semi-double, began as narrow-petaled flowers without ruffling. As hybridizers worked on improving the doubles, the new flowers emerged with wider petals and ruffles, giving them a more finished look. Through generation after generation of double breeding, the blooms became more consistently and fully double. During the 1980s and 1990s double tetraploid daylilies emerged, with heavier substance and clearer, brighter colors. Like tetraploid singles, initially there were no tetraploid doubles with which to work, which made the first efforts to produce tetraploid doubles ardous and slow.

Form of doubles

To simply appreciate the exquisite beauty of double flowers it is not necessary to know the intricacies of their form. However, an even greater appreciation of double daylilies will result from understanding the way they are made. The double daylily is somewhat complex and ever changing and is worth a few extra minutes spent to study its nature.

An attempt at understanding and classifying double daylily forms is not new, and different individuals use different terms to describe daylily types. In 1945 in Herbertia, A. B. Stout published a description of the forms of doubling he observed along with suggested names for those forms. Some of his terms are still used more than 50 years later, however, no standard method of classifying doubles has yet been agreed upon.

Double daylilies are derived from single daylilies. The normal single daylily has three sepals, three petals, and six stamens. The daylily is made of four whorls or layers: (1) the sepals, (2) petals, (3) stamens, and (4) the pistil. The ideal way to form a double flower would be to add extra layers to the whorl of petals, creating multiple layers of petals. However, most double daylilies are formed by modifying the stamens.

Most double daylilies are created through the formation of petaloids. Though they look like extra petals, petaloids are stamens with extra tissue along their sides. Some flowers add tissue to only one side of the stamen-these petaloids are easy to recognize as modified stamens. Other flowers add tissue to both sides of the stamen-these resemble true petals, although the anther, or pollen sac, can generally be found on the petaloid. Sometimes, the anther becomes rudimentary or even non-existent, so that the petaloid looks like a perfectly normal petal. Since petaloids are formed from the stamen tissue and daylilies have only six stamens, six is the maximum number of petaloids that a daylily can have. If it has less than six petaloids, the remaining stamens will be normal, and the flower will appear semi-double. Double flowers of most other genera contain extra layers of true petals, not simply modified stamens, and typically contain many more than six extra petals. Daylilies, therefore, are quite different from other double flowers.

Some double daylily flowers add tissue at the midrib of the petaloid. This midrib tissue usually projects upward and outward from the center of the petaloid, resembling the wings of a butterfly. The form of midrib tissue can vary. Some petaloids contain only a single wing, many petaloids have two wings, and occasionally each individual wing can appear as two parallel layers of tissue. Midrib tissue gives the appearance of even more petals, giving the flower added fullness, particularly as this tissue becomes large and ruffled.

Some "apparently single" daylilies, which contain only three true petals, also have extra tissue rising up from the midrib of the petals, similar to the extra tissue on petaloids. This formation has caused some disagreement as to whether these flowers should be classified as singles or doubles-currently they are referred to as "midrib doubles." Some people insist that these flowers are single since they have only three true petals. Others argue that if doubles can be produced by forming petaloid tissue from stamens, they can also be produced by forming petaloid tissue from petals. Midrib doubles, then, are flowers with only three true petals, with extra tissue generated from, or fused to, the midrib of those three true petals. This tissue is typically formed from the middle of the petal at 45- to 90-degree angles, resembling the two wings of a butterfly. The fact that midrib tissue can form on either the three regular petals of an otherwise single flower or on the midrib of petaloids indicates that this is an inherited characteristic in daylilies potentially separate and distinct from the production of extra petals or stamen-derived petaloids.

All of this is very different, however, from adding extra true petals. Flowers with extra true petals, called supernumerary doubles, or sometimes "super-doubles," are rare in daylilies. Supernumerary doubles stack on additional layers of petals and retain their normal stamens. They typically have nine petals, six extra, along with all six stamens. Since these doubles have their stamens intact, they have the potential to turn their stamens into petaloids. Such flowers would then have nine petals plus six petaloids, for a magnificent total of 15 colored segments.

Unlike petaloids, which are limited to six, the possible number of extra true petals seems to be unlimited. Theoretically, many layers of petals could be stacked one on top of the other, to produce a double daylily with the number of petals of a rose or camellia. The sterile Hemerocallis fulva var. kwanso and H. fulva 'Flore Pleno' are supernumerary daylilies with many columns of true petals. Although most daylily enthusiasts feel that these species plants lack much of the beauty of modern hybrids, they do have a form as yet unachieved among modern daylilies. However, after many decades of work, hybridizers are beginning to produce supernumerary double daylilies, leading the way in an area for further daylily breeding.

Double daylilies can also be categorized according to the form of the extra petals or petaloids. The two primary groups are the hose-in-hose types and the peony types. Hose-in-hose are flowers in which the petals or petaloids lie flat in layers, resembling the look of extra true petals. This gives the flower an appearance similar to a camellia or fully opened rose. Any petaloids are usually full, not half petaloids, and there is usually no midrib tissue.

In other doubles, the petaloids stick up in the center of the flower, pointing outward like stamens. This form is referred to as peony or cockatoo. The petaloids can be either half or full and may or may not have midrib tissue.

Do not think too rigidly about double daylily forms. The double form of a daylily can vary from day to day within an individual cultivar or even on a single plant, and new double forms are continuously emerging. Further, many cultivars that produce double flowers also produce single flowers, particularly early in the season. The degree of doubling appears to be temperature dependent -many of these cultivars produce single flowers in cool weather but bear more frequently double flowers as the weather warms.

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