Citrus - Lemon Citrus ×limon (L.) Burm. f. Rutaceae

Species description Lemon trees are erect and spreading, with sharp thorns on the branches and twigs. The leaves are alternate, oblong to elliptic, finely toothed on the margins, with slender wings on the petioles. Lemon flowers are mildly fragrant, white to light purple in color, and appear in small clusters on the leaf axils. Lemon fruit is oval with a nipple at the apex, usually light yellow at maturity. The fruit is highly aromatic and covered in oil glands. The pulp is pale yellow with 8-10 segments, juicy and acidic. Lemons may be harvested year- round; they do not become dormant in the winter, and will produce flowers throughout the year. Lemon trees can grow 20-30 feet tall with a canopy diameter of 20 feet, and may live for over 50 years. Lemon trees, similar to other citrus are hardy to 23ºF-26ºF, though this may depend on cultivar. Trees tend to be more frost sensitive when young and should be protected during cold temperature spells.

Natural and cultural history The ancestral home of the lemon is unknown, though it is considered to possibly be northwest India. The lemon was introduced to Mediterranean Europe from Asia around 200 CE. It was cultivated in Iraq and Egypt around 700 CE. Arabs distributed the lemon widely around the Mediterranean region by 1150 CE. Christopher Columbus carried lemon seeds to the New World in 1493. Commercial plantings began in California and Florida in the late 1800s. California and Arizona became the leading lemon producers in the western Hemisphere.

Planting considerations and propagation techniques The improved Meyer Lemon is slightly hardier than the true lemon and may be a better choice for home gardeners in colder desert climates. Lemon trees prefer full sun, and should be spaced at least 25 feet from other trees for full fruit production. Citrus trees are very spiny so care should be taken in their placement, especially in public spaces. Citrus flowers are self- fertile and require no cross-pollination, though honeybees are effective pollinators. Citrus can grow on a wide range of soil types from sand to loam to heavy clay as long as they are well drained. The ideal soil pH for citrus trees is 6-6.5, though different rootstocks prefer different soil types. Most commercial lemon trees are grafted onto other citrus rootstock to preserve the variety. Meyer lemons, however may be propagated by rooting large cuttings. These rooted cuttings will fruit two-three years earlier and may remain in production for at least 30 years.

Water needs Citrus need about 4-6 inches of water per month in the summer; they are generally not drought tolerant and need careful attention to produce well-developed fruit.

Care Citrus trees should be trained to a suitable shape with an open center. There are three primary pruning objectives: increase total leaf area, improve airflow through the canopy, and increase light to the branches. Proper training keeps trees the correct size for ease of care and harvest. Citrus are prone to many diseases and pests. We recommend consulting a Cooperative Extension citrus specialist. (See Yuma Cooperative Extension, https://extension.arizona.edu/yuma; and http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1492.pdf).

Harvesting and processing Citrus should be harvested when it has full color and can be eaten immediately. The tree is the best place to store citrus. Lemons may be harvested throughout the year. Lemon juice may be used fresh, canned, concentrated and frozen for lemonade and other beverages. The juice is also used as a flavoring or component in pies and tarts, cakes, cookies, cake icings, frozen deserts, and preserves. The juice is also made into syrup. Lemon peels may be candied and used as zest for salads, meat dishes, sugar products and baked goods. Lemons are often cured in salt and used in Mediterranean cooking.

References and resources AZ Citrus. http://www.azcitrus.com Gmitter, F.G., J. Soneji, M.N. Rao, and S. Huang. Citrus spp., pp. 773-784. Eds. Janick, J. and R.E. Paull. The Encyclopedia of Fruit and Nuts. CABI Publishing, Cambridge, MA. Morton, J. 1987. Lemon, pp. 160–168. In: Fruits of warm climates. Julia F. Morton, Miami, FL. https://www.hort.purdue.edu/newcrop/morton/lemon.html Page, M. 2008. Growing Citrus: How to Grow Citrus in Containers, Conservatories, and the Open Garden. Timber Press, Portland, London. Plants for a Future (PFAF). n.d. Citrus limon - (L.)Burm.f. http://www.pfaf.org/user/Plant.aspx?LatinName=Citrus+limon Soost, R.K. and M. Roose. 1996. Citrus, pp. 257-324. Eds. J. Janick and J.N. Moore. Fruit Breeding, Volume I Tree and Tropical Fruits. John Wiley & Sons, New York, NY. University of Arizona Cooperative Extension. 1998. Low desert Citrus varieties, publication AZ 1001. http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1001.pdf University of Arizona Cooperative Extension. 2000. Irrigating citrus trees, publication AZ 1151. http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1151.pdf

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