GROWING CITRUS Page 1 GROWING CITRUS IN THE Publication Number 31-018C SIERRA NEVADA FOOTHILLS (March 2010) AUTHOR: Cindy Fake, Horticulture and Small Farms Advisor, Nevada & Placer Counties Mandarins are the signature Mandarins dominate commercial Meyer lemon (22°F) > oranges - fruit of the Sierra Nevada citrus production in the Navel, blood, etc. (24°F) > foothills. Warm days and cool foothills, but many other citrus grapefruit (26°F)> true lemons nights during the growing species can also be grown. (Eureka, Lisbon) (28°F)>lime season provide near-perfect Navel, blood, and Valencia (30°F). Low temperature conditions for production of oranges, lemons, limes, tolerance depends on many high-quality flavorful fruit, the grapefruit and kumquats are all factors, including tree age, produced commercially in the nutritional status, soil water Mountain Mandarin®. Recent research has also revealed that foothills. Microclimates created status, acclimatization, and fruit mandarins contain significant by foothill topography also maturity, among others. These amounts of synephrine. allow production of more exotic temperatures are guidelines, Synephrine is a natural citrus species such as pommelo, given to assist in selecting antihistamine, which can shaddock, limequat, appropriate species. All of the alleviate the symptoms of colds calamondin, and yuzu. Not all citrus species cited can and allergies, so mandarins are varieties can be grown in all successfully be grown in the also health foods. microclimates, however. For right microclimate of the lower more information on citrus foothills. Commercial mandarin varieties, see UCCE Publication production flourishes in the 16C: Citrus Varieties for the foothills at elevations from 400 Foothills. to 1000 feet. Most of the Eco-requirements production is Owari Satsuma for citrus production mandarins: sweet, seedless, zip- skin fruit. A few other varieties Site Selection of Satsumas and some The best sites for citrus are ridgetops or south-southwest Clementine mandarins are also Citrus are subtropical in origin, produced. facing upper slopes, with good thus the cold temperatures cold air drainage. Impediments which occur occasionally in the to cold air drainage such as foothills can pose significant risk vegetated fence lines, brush, of frost and freeze damage. blackberries, or hills may cause Tolerance to cold temperatures cold air to back up and damage varies among the citrus species. the orchard. Mandarin is among Kumquat (18°F) is hardier than the most cold-hardy of citrus, Satsuma mandarin (20°F) > COOPERATIVE EXTENSION, UNIVERSITY OF CALIFORNIA Placer County WEB SITE: ceplacernevada.ucdavis.edu Nevada County The University of California prohibits discrimination or harassment of any person in 11477 E Avenue, DeWitt Center The University of California, in accordance with applicable Federal and State law and University 255 So Auburn Street. any of its programspolicy, does or not activities.discriminate on the (Complete basis of race, color, nondiscrimination national origin, religion, sex, disability, policy age, statement can Auburn, California 95603 medical condition cancer.related., ancestry, marital status, citizenship, sexual orientation, or status Grass Valley, California 95945 be foundas a Vietnamat http://groups.ucanr.org/ANR_AA/files/54634.pdf)..era veteran or special disabled veteran. Inquiries regarding the University’s nondiscrimination policies may be directed to the Affirmative Action Director, University of California, 530.889.7385 Direct inquiriesAgriculture regarding and Natural Resources, the University’s 1111 Franklin, 6th Floor,nondiscrimination Oakland, California 94607 .5200.policies 510. to the Af- 530.273.4563 FAXUNIVERSITY 530.889.7397 OF C ALIFORNIA COOPERATIVEfirmative Action E Director,XTENSION University 987.0096. of California, ANR, 1111 Franklin St., 6th PLACER & NEVADAFAX 530. COUNTIES273.4769 United States Department of Agriculture, University of California, Placer and Nevada Counties E.Mail: [email protected] Floor, Oakland, CA94607,cooperating. (510) 987-0096. E.Mail: [email protected] GROWING CITRUS Page 2 however, elevation does limit For home plantings of a few foothill soils, as long as they are production. In general, the upper trees, planting next to south- on slopes or soils that drain well. limit for citrus orchards is about facing cement or stone walls or a Clay soils have smaller pore 1,200 feet elevation. patio can mitigate the risk of spaces and absorb more water cold. The stone or cement than granitic soils, so the danger In some areas, absorbs heat during the day, and of waterlogging is greater. Citrus foothill reradiates it back at night, do not tolerate waterlogged roots topography protecting the trees. In marginal and are susceptible to creates zones, containerized trees in wine Phytophthora root disease when locations barrels or tubs can be moved they are overirrigated. Do not where next to south facing walls, or plant citrus in lawns or in areas temperatures indoors for protection in cold which become saturated with are much more weather. winter rains. Plant in raised beds moderate than or mounds if waterlogging is a one would expect for a given If you are interested in planting risk. elevation. These are the so-called mandarins in the foothills, but “banana belts” or warm are unsure of the suitability of Foothill soils typically have low microclimates where citrus your property, it is best to collect native fertility and organic production may be possible temperature data for your matter. Many foothill soils are above 1,200 feet. Citrus particular site for at least a year. clay or decomposed granite and production may also be possible Purchase several maximum/ quite acidic (pH <7). At lower at higher elevations in an area minimum thermometers and elevations, there are more neutral where frost risk is moderated by place them around your and slightly alkaline soils. Citrus a large body of water, pavement, property, especially up and down grow well in slightly acidic soils, or warm upwinds from a canyon slopes, to gauge where cold air but a very acidic soil (below pH or lower elevation. backs up the slope. Record 6) will need to be amended with minimum temperatures lime to correct pH. Citrus require full sun for throughout winter and spring, at flowering and fruit production. A least on a weekly basis. An analysis by a professional soil citrus orchard should be as laboratory is recommended sheltered as possible from strong Soil Conditions before planting. Your winds. Mandarins, in particular, amendment and fertilizer should be protected from winds, Citrus are shallow-rooted trees. program will depend on the without impeding cold air Feeder roots are in the top two results of your soil tests. In order drainage. Their thin rind is feet of soil, with most activity to avoid costly errors, it is best to susceptible to damage from wind occurring in the top 12 inches. use a commercial lab rather than and wind-driven rain from winter Deep soil is not necessary for home soil test kits. See UCCE storms and damage is successful production as the publication 74C: Soil Analysis for exacerbated by cold majority of commercial information on area soil weather. Sites offering mandarins in Placer County are laboratories and analyses. protection from wind will also grown on 18 inches of soil or less. increase the available heat for You will need a number of the trees in frost/freeze events. Citrus do not require deep soils, standard soil tests to provide a but they do need well drained baseline for your soil soils. They will grow well on most management program. Most labs UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION ceplacer.ucdavis.edu GROWING CITRUS Page 3 have a basic package, which future, so it is best to start with for container citrus, but not for provides a good baseline. You high quality planting stock. production orchards. Carrizo should have your soil analyzed rootstock is sometimes used in for: Citrus grown for fruit the foothills, producing high production are almost quality fruit, but later in the pH: acidity or alkalinity exclusively budded trees. Very season. Carrizo does not impart soil nutrient status: at N, P, few citrus are grown on their quite as much cold tolerance as K at a minimum; Ca S, Zn, B own roots because they are not Trifoliate, however. Older trees and Fe are recommended. as productive as those grown on are often on Cleopatra rootstock. rootstocks. Budded trees will However, Cleopatra has no CEC (Cation Exchange consistently produce the same dwarfing characteristics, and Capacity), a measure of true-to-type fruit. Very few trees will become very large, so native fertility citrus fruit produce seed that it has fallen out of use. organic matter will come true to type. Planting a seed from a citrus fruit rarely The valley citrus industry ppm (parts per million) of gives you a tree that produces standard is a rootstock called C- Ca, Mg, K, and Na (base the same fruit, and without a 35. It is preferred there because saturation %) rootstock, it will probably be a it begins to bear earlier than Ca: Mg ratio weak tree. trees on Trifoliate rootstocks. Some foothill orchards are on C- Use a California lab to get Rootstocks 35, however, it has a number of accurate information. If you drawbacks for the foothills. C-35 inform the lab that you will be Each citrus does not provide as much cold planting citrus, they can provide tree has two resistance, and young trees are recommendations on the parts: the often severely damaged by frost. nutrients or amendments rootstock and The C-35 rootstock is very needed. Most labs will give the scion. The vigorous and overgrows the guidance on organic rootstock is a scion, reducing the longevity of amendments, if you specify that species selected for specific the orchard. In addition, the it is organic. For more characteristics, such as disease consensus among foothill information on organic resistance or tolerance of certain growers is that C-35 fruit are not amendments, see UCCE soils.