ORNAMENTAL USE OF WILD SPECIES OF GENUS GLADIOLUS

Abstract

Two Mediterranean species of genus Gladiolus were studied in order to diversify the range of ornamental plants on offer: G. illyricus for use as a rockery plant and G. italicum preferably for use as a cut flower, although it could be used in gardening. Both species can be sexually or asexually propagated, although seed production is higher than cormels production in both species. The growth and development characteristics of both species were tested both in their natural habitats and in an unheated greenhouse. Plants cultivated in the greenhouse grew faster and were larger. The length of the floral spike was also greater. The time elapsing to the onset of flowering was almost four months in G. italicus plants grown in the greenhouse and three months in G. illyricus. We suggest that more studies are necessary in order to understand the behaviour of these Gladiolus species whether grown in the open air or in the greenhouse. INTRODUCTION There is growing interest in the use of native Mediterranean species for ornamental purposes, both for their capacity to adapt to a variety of environmental conditions and because of the potential for saving water. The ornamental plant sector is changing as consumers look for new and original material, as is reflected by the incorporation of autochthonous plants on the market. Furthermore, in most European countries the demand for traditional ornamental products (except roses) is falling and new species and cultivars are constantly being sought. The fashion is for cut flowers which look like wild flowers (Chimonidou-Pavlidou, 2000). The genus Gladiolus is widely distributed throughout the world (Lewis et al., 1972). Both Gladiolus italicus Ker-Gawler (syn. G. segetum) (Goldblatt, 1994), that is distributed throughout southern Europe, North Africa, SW Asia and Macaronesia, and G. illyricus Koch., that is distributed throughout S and W Europe, North Africa and Western Asia, are widely present in SE Spain. The first is found more inland, while the second is abundant in all areas. The climate where they are found is dry, with mild winters, in which conditions G. italicus grows to between 40 and 110 cm in height with a spicate inflorescence consisting of 5-10 flowers with pink tepals; G. illyricus shows a certain botanical similarity but is shorter and with fewer number of leaves (Sanchez et al., 1994). Their growth cycle in their natural habitat begins in the autumn when shoots appear and finishes in early summer with fruiting. Once domesticated, G. italicus is suitable for use as a cut flower (although also in garden displays) while G. illyricus is more suitable as a rockery plant. The object of the study we describe was to compare the behaviour of both species in their natural habitat and in their cultivated form to determine their possible use as ornamental plants. MATERIAL AND METHODS Gladiolus illyricus and G. italicus were used in this experiment. The corms used for planting in the greenhouse, came from Murcia (SE of Spain) and Ibiza (Balearic Islands) and were harvested the year prior to the experiment. Plants of the same species Proc. IS on Sust. Use Of Plant Biodiv. Eds. E. Duzyaman Y (ii) flowering stem quality, represented by the flowering stem and spike length and number of buds per flowering stem and (iii) the yield and earliness of the crops, measured as the number of flower stems per corm and the number of days from planting to the onset of flowering. RESULTS AND DISCUSSION The climatological data recorded during the experiment were normal for the area concerned (Fig. 1). In the case of G. illyricus, the mean temperature between October 2000 and May 2001, when the experiment took place, was 14.9oC, while the accumulated rainfall was 238 mm with a maximum of 122 in October. The average temperature of the habitat where G. italicus grew was 11.7oC while the accumulated rainfall was 285 mm, with an October maximum of 152 mm. In the case of the cultivated plants the mean greenhouse temperature during growth was 15.9oC. The number of seeds produced per fruit was quite irregular and independent of the original corm size (Table 1). G. italicus plants growing in the wild produced more seeds than their greenhouse-grown counterparts (maximum and minimum numbers of 19.5 and 2.6 in the wild and 14.2 and 4 in the greenhouse). In both the wild and cultivated plants grown there was a direct correlation between the number of fruits produced and the calibre of the corm used. The fruits nearest the apex contained the highest number of seeds. On the other hand, the number of seeds produced by G. illyricus was greater in cultivated plants (34-20 seeds maximum and minimum compared with less than half that number in wild plants). Similarly, the wild plants produced substantially fewer fruits than their cultivated counterparts (two compared with the five fruits of cultivated plants) As regards the vegetative reproduction of the corms, the number of principal and secondary corms obtained at the end of flowering was counted, recording only the subterranean corms produced near the mother corm, although axillary subterranean corms produced above the mother cormels where the leaves began were also evident (usually a small corm of 1/2 calibre although occasionally a bunch of the same). In general the number of cormels produced was substantially less than the number of seeds (Table 1 and 2). Of note is the fact that in G. italicus the number of cormels produced was greater and their size larger when large corms were used to produce plants (Table 2). Regardless of the size of corm used, cormels production by wild plants was greater than in the cultivated plants, although the existence of cormels produced previously may have been responsible for this greater number. Whatever the case, it would be worth studying the root system of growing plants in greater depth, particularly gladiolus contractile roots, since these contribute 22.4 % to the enlargement of the corms (Kawa and De Hertogh, 1992; Iziro and Hori, 1983) Normally, the length of the leaves was greater in each successive leaf, except the