• Assaf Avtabi 
• Joshua D. Klein 

Etrog fruits are grown in only a few of the many countries that produce citrus. The fruits are unusual among citrus in that the vast majority of the crop is valued only for its external appearance, and is produced and sold to a particular ethnic-religious market. Etrog trees must be grown in frost-free areas with little wind and good soil drainage. The trees are easily rooted and established from cuttings, although there is a danger of transmission of disease by this method. Trees can also be grown from seed, which mitigates disease transmission. However, seed-derived trees are not always identical to the mother plant. Trees are best established in Spring, for religious (counting of the orla years) and horticultural (gaining strength before Winter) reasons. Etrog trees are usually trained to a trellis system for ease of access to fruit, and are grown on raised beds for ease of rooting, with trickle irrigation for directed fertilization, and under shade cloth to protect the trees and especially the sensitive fruit from solar damage. Maintenance of fruit quality requires repeated spraying of various compounds, but spraying is minimized later in the season to avoid peel stains that make the fruit unmarketable. A unique spray treatment is the use of Picloram early in the season for retention of the style (“pitam” in Hebrew), which enhances marketability of the mature fruit. Although etrog trees flower three times a year, selective drought in the Spring is recommended to suppress the early wave of flowering, which often produces less-marketable fruit. Etrog fruit are highly variable in shape, and not all shapes are accepted commercially. Commercial orchard yields are maintained for 12–14 years, after which the yield decreases, partly because of tree age and partly because of heightened sensitivity to disease.