Growth and nutrient partitioning of containerized Cercis siliquastrum L. under two fertilizer regimes Hala G. Zahreddine a,1 , Daniel K. Struve a, * , Salma N. Talhouk b a Department of Horticulture and Crop Sciences, The Ohio State University, Columbus, OH 43210, United States b Faculty of Agriculture and Food Sciences, The American University of Beirut, P.O. Box 11-0236, Beirut, Lebanon Received 3 March 2006; received in revised form 9 October 2006; accepted 22 November 2006 Abstract Lebanon’s native flora is threatened by loss of natural habitat to rural and urban development and the increased demand of plant materials for landscaping. Despite Lebanon’s floristic richness, most taxa used for landscaping are non-native. This study was done to determine if Cercis siliquastrum (L.) is amenable to container production. Therefore, six open pollinated seeds sources native to Lebanon were grown under two fertilizer rates to study growth, N, P, K uptake efficiency, and partitioning. Two-year-old seedlings were planted in 11L containers in a 3:1 pine bark:compost substrate. Seedlings within each seed source or mother tree were grown at either 25 or 100 mg N L 1 from 21N–3.1P–5.9K water- soluble fertilizer. Seedlings of all sources grown under 25 mg N L 1 had greater dry weight than those grown at 100 mg. Nutrient loading occurred in plants under the high fertilizer rate, although total plant N, P, and K content were not affected by fertilizer rate. There were significant differences in mineral nutrient uptake and nutrient use efficiencies among the seed sources. The results show that C. siliquastrum is amenable to container production. The great variation in growth rate and nutrient use efficiency among the limited number of seed sources studied suggest that significant improvement can be made through mother tree selection and/or clonal propagation of superior individual plants within a source. # 2006 Elsevier B.V. All rights reserved. Keywords: Judas tree; Lebanese flora; Container production; Relative growth rate; N–P–K ratios; Mineral nutrition; Woody ornamentals; Nutrient loading 1. Introduction Lebanon falls within an identified center of plant diversity, the Levantine uplands (Davis et al., 1995). Lebanon has an estimated 3761 vascular plant species (UNEP, 1996). This unique flora is threatened by tourism, urban expansion, and proliferation of summer resorts in the mountains (UNEP, 1996). After 1990, private gardens began to redevelop and only recently have public and private landscaping been rediscovered. Despite Lebanon’s floristic richness, most taxa used in landscaping are non-native. Most plants used in Lebanese landscape are imported from Spain, Syria, Egypt, and the United States, but Italian imports dominate. Many native plant species have outstanding ornamental value and are likely better-adapted to local conditions than exotic taxa. However, the concept of using endemic taxa for ornamental purposes has not gained wide acceptance. In contrast, in neighboring Turkey, studies are being conducted to optimize the domestication of wild plants with ornamental value (Ertug Firat and Tan, 1997). One native Lebanese species with ornamental potential is Cercis siliquastrum, Judas tree (Fabaceae). It has a mature height of 5–10 m. When young it has purple-tinged bark color which becomes gray-pink with age (Anon., 1999). The leaves are bluish green with rounded tips. It flowers from March to April before leafing out. The flowers are pink, usually borne in clusters of three to six on previous years’ growth. It is widely distributed in the Thermomediterranean zone (0–500 m altitude) and can be found from sea level to 800 m altitude where it is associated with pine and oak forests. In its native range, most (80–90%) of the annual rainfall (700–1000 mm) occurs between November and March; less than 5% occurs between May and September. Its wide distribution range over diverse habitats suggests that provenance differences may exist. Like other redbud species, it is reported to grow in a variety of soil types (Anon., 1999; Burns and Honkala, 1990). Redbud species tend to be tolerant of nutrient deficient soils (Burns and Honkala, 1990). C. siliquastrum grows best in full sun, and can www.elsevier.com/locate/scihorti Scientia Horticulturae 112 (2007) 80–88 * Corresponding author. E-mail addresses: Zahreddine.1@osu.edu (H.G. Zahreddine), struve.1@osu.edu (D.K. Struve). 1 Tel.: +1 614 292 3853; fax: +1 614 292 3505. 0304-4238/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.scienta.2006.11.013