Foreword

The day daylily (Hemerocallis, Eng. daydaylily) is such a well-known plant and has been described in so many sources that I can omit its general characteristics and the advantages it offers as an ornamental plant. From a breeding point of view, as this aspect constitutes the main body of this work, it is important to divide the daydaylilies into two fundamental groups based on the number of chromosomes which are found in the cell nucleus: those which maintain a count of 22 chromosomes, known as diploids, and those whose number has been doubled as a result of cultivation, known as tetraploids. Although it is impossible to determine with any certainly which of the two categories a plant belongs to just by looking at it, tetraploid daylilies are generally larger and stronger, with a stronger build and with larger flowers than diploid forms. Note that it is recommended that plant cross-breeding should be carried out within each group that is diploids with diploids or tetraploids with tetraploids. Pollination between groups, although theoretically possible, is not performed under amateur cultivation conditions, because as a rule, such cross-breeding is not effective. Another criterion for classifying daylilies is based on whether they keep their leaves under demanding conditions in response to changes in climate during the annual cycle of vegetation. Three groups can be distinguished; two stand iat opposite ends : deciduous plants, which drop their leaves in winter, and evergreens, which keep their leaves the whole year round. There is also an intermediate form – the semi-evergreen. However, since daylilies are grown at all latitudes in very different climatic conditions, and because of the resulting intermediate forms of the crosses, the classification has limited practical significance. It is generally accepted that in a temperate climate, which is where Poland finds itself, transitioning between oceanic and continental climates, it would be advisable to concentrate on keeping semi-evergreens or deciduous daylilies, taking care against winter. Limited experience in keeping winter and semi-evergreen daylilies in our country, as well as climate changes in our latitude in recent years characterised by relatively mild winters, do not allow a clear unequivocal answer to this question. Adapting winter and semi-evergreen daylilies to our climate is so important as plants of particular decorative value and the possibility of cultivating them in our conditions for use in cultivation improves them in a fundamental way. Concerning the breeding of daylilies, it should be kept in mind that although the most attractive and desired part is the flower, it is only one component equipped by nature along with other features no less important in garden practice. Such characteristics are: the flowering period, flower size, stem height, number of flowering buds on the stem, method of structuring activities during the flowering period, durability of flower colour, the length of time before the flowers are dropped, resistance to changes in climate and illness, smell, fecundity, fertility - and maybe others acting synergistically to enhance the value of the plant. Bearing all this in mind, only the daylily flowers are addressed in this part, since they stand proudly as a rich testament to the progress made in keeping daylilies during recent years.