Silber, A., Institute of Soils, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel
Ben-Jaacov, J., Department of Ornamental Horticulture, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel

Two agro-technical methods are feasible for overcoming the soil limitations that impede the cultivation of Leucadendron 'Safari Sunset' in Israel: (i) improving the rhizosphere conditions; and (ii) grafting sensitive cultivars on resistant rootstocks. To improve the rhizosphere it is possible to improve a restricted volume of the root zone by using a small volume of artificial substrate and/or by employing nutritional management that reduces the pH. The common horticultural practice in Israel is to plant L. 'Safari Sunset' in tuff-embedded in the native soil. Usually, there are no barriers to the free extension of roots from the tuff into the native soil. Thus, roots develop under two different environments: (a) a fixed volume (usually 30-50 L) in the vicinity of the plant, where the tuff properties ensure that the drainage and the pH are suitable for plant growth; and (b) the surrounding native soil, where air deficiency or high pH may restrict plant development. An alternative approach is to graft the sensitive plant (scion) onto a soil-adapted rootstock (method (ii)). Some years ago, some species native to high-pH soils in South Africa were studied as potential rootstocks for Israeli conditions, and the best-growing variety of Leucadendron coniferum, 'Orot' was selected. 'Orot' is currently widely used as the rootstocks for L. 'Safari Sunset'. Several studies have shown that the growth of grafted plants was significantly superior to that of ungrafted plants and that this advantage was more significant under conditions of nutrient deficiency and non-optimal pH.