Plant Answers  >  'Orange Frost', a new cold hardy citrus

"Orange Frost", a new cold hardy citrus

Larry Stein, Jerry Parsons, Leon Macha, David Rodriguez, Monte Nesbitt and Brent Pemberton

Professor and Extension Horticulturist, Department of Horticultural Sciences, Texas AgriLife Research and Extension Center, P.O. Box 1849, Uvalde, TX.

Professor and Extension Horticulturist (retired), Department of Horticultural Sciences, Texas AgriLife Extension Service, San Antonio, TX.

Vice President of Operations (retired), Greenleaf Nursery, El Campo, TX.

Bexar County Horticulturist, Texas AgriLife Extension Service, San Antonio, TX.

Program Specialist, Department of Horticultural Sciences, Texas AgriLife Extension Service, College Station, TX.

Professor, Department of Horticultural Sciences, Texas AgriLife Research and Extension Center, Overton, TX.

Satsuma mandarins (Citrus unshiu Marc.) are among the most cold hardy citrus varieties that have sufficient fruit quality for potential commercial marketing as well as for homeowners outside the typical citrus belt in the Lower Rio Grande Valley (Mortensen, 1983). Satsuma mandarin was first reported in Japan more than 700 years ago where it is now the major cultivar grown, but more than likely it originated in China (Ferguson, 1996). The first recorded introduction into the United States was in Florida by George R. Hall in 1876 (Ferguson, 1996). The name “satsuma” is credited to the wife of the United States minister to Japan, General Van Valkenberg, who sent trees home in 1878 from Satsuma where it was believed to have originated (Ferguson, 1996). While this fruit is primarily grown for fresh consumption, a portion of the crop is canned as fruit segments or juice in Japan, China and Spain. In these countries, deeply colored juice is blended with orange juice to improve color or sold as single-strength tangerine juice. Fresh fruit is also imported into Canada and non-citrus producing areas of the U.S., where it is the earliest seasonal citrus crop to reach market (Ferguson, 1996).

Approximately one million ‘Owari’ Satsuma trees were imported from Japan (1908-1911) and planted throughout the lower Gulf Coast states from the northern Florida Gulf coast to Texas, where an extensive tangerine industry developed (Ferguson, 1996). The earliest citrus in Texas was from seed planted in dooryards by the early settlers (Mortensen, 1983). The coastal area near Houston and Beaumont had a citrus “boom” until February, 1911, when the temperature dropped to -13.3 C at Alvin. Most growers were lucky to save 10 percent of their trees. This was followed by the 1915 hurricane, so the Texas Orchard Development Company moved its operations to the Lower Rio Grande Valley where a railroad had recently been built. The Texas Experimental Station at Beeville was also growing citrus and reported success with satsumas in a publication in 1909. There were an estimated 800 acres of trees in the Winter Garden (Uvalde-Crystal City-Pearsall) in 1945 (Mortensen, 1983).

Satsumas have been observed to tolerate temperatures of -9.9 to -11.0 C without injury if trees are totally dormant and the temperature doesn’t remain there more than 3 hours (Ferris and Richardson, 1923; Mortensen, 1983; Ferguson, 1996).

Because of their low total heat requirement, some Satsuma cultivars ripen earlier than most other citrus. Hence, the Satsuma is ideally adapted to regions with winters too cold for other citrus fruit but with growing seasons warm enough to produce fruit of early maturity and good quality. The range of climatic adaption for commercial culture is therefore narrow and restricted to the higher elevations and colder areas of the sub-tropical zones. Although these areas are subject to severe freezes, current cold protection methods, using in-tree micro sprayers, can protect trees to a height of approximately four feet. This cold protection strategy may be the key to at least partial revitalization of Satsuma planting in these areas (Ferguson, 1996).

Another possibility is new more cold hardy varieties. Trifoliate orange is the most cold hardy citrus though its fruit are for the most part non-edible ( Nagle, 1997). Numerous crossed have been made with trifoliate orange to capitalize on this cold hardiness, however for the most part the fruit quality remains poor (Nagle, 1997). ‘Chansha’ tangerine which originated in the foothills of China also has exceptional cold tolerance, but has fair fruit quality having numerous seeds per locule (Sauls, 1981) ‘Changsha’ appears to a hybrid which includes Ichang Papeda (Nagle, 1997). Ichang Paapeda is probably the most cold hardy of the evergreen species of citrus and it is native to the warm temperate inland areas of China (Nagle, 1997). Crosses between ‘Changsha’ and Satsuma could increase cold tolerance and maintain fruit quality.

Such a cross resulted from a controlled breeding program in San Antonio, TX, U.S.A. The overall purpose of the breeding program is the creation of Satsuma and tangerine hybrids that exhibit the cold tolerance of the tangerine, but maintain the Satsuma fruit quality.

‘Orange Frost’ was selected by Ying Doon Moy in 2005 as a single unique tree that resulted from an embryo rescue of a seed obtained from a cross made by Moy in 1998 between the tangerine Citrus reticulate ‘Changsha’ , and an unnamed seedling of a mandarin Citrus reticulate var. unshui (syn, Citrus unshui) as the male parent.

Asexual propagation of the new cultivar was first accomplished by stem cuttings in San Antonio, TX in 2005 by Larry Stein and Jerry Parsons. It has been determined that the characteristics of this cultivar are stable and re reproduced true to type in successive generations.

The following traits have been repeatedly observed and represent the characteristics of this new cultivar of citrus. ‘Orange Frost’ has been observed to be cold hardy to at least -11.1 C (defoliation occurs at temperatures below about -9.4 C; foliage is evergreen above -9.4. The fruit is similar in quality to high quality Satsuma type trees with few seeds present (0 to 4 per fruit). In addition the fruit is sweet with a tinge of tartness and has an easy to peel skin. ‘Orange Frost’ is readily distinguished from its female parent plant ‘Changsha’ as it is a more spreading tree. Although ‘Changsha’ exhibits slightly better cold hardiness, the fruit of ‘Orange Frost’ is much improved as the fruit of ‘Changsha’ is less flavorful, has abundant seeds and is more difficult to peel. In comparison to the male parent, a Satsuma type seedling selection, ‘Orange Frost’ is more cold hardy and the fruit is a bit more tart. ‘Orange Frost’ can be compared to Citrus reticulate var. unshiu ‘Seto’. ‘Seto’ is less cold hardy than ‘Orange Frost’.

Average fruit size of ‘Orange Frost’ is 10 cm in diameter and 9 cm in height with an oblate fruit shape. It has an easy to peel skin, 0.5 cm in thickness. The flesh color is orange, 24 A (RHS, 2007) with juicy flesh and an average soluble solids of 12.

‘Orange Frost’ is exclusive to Greenleaf Nursery in El Campo and will not be available for general release until 2014. Greenleaf Nursery has applied for a plant patent, docket No. 201008 on this variety.

Literature Cited
Ferguson, J.J. 1996. The “The Orange Frost citrus is currently exclusive to Greenleaf Nursery in El Campo and will not be available for general release until 2014,Satsuma Tangerine. University of Florida Fact Sheet. HS 195.

Ferris, E. B. and F. B. Richardson. 1923. The Satsuma Orange in South Mississippi. Ms. Ag. Exp. Sta. Bul. No. 217.

Mortensen, Ernest. 1983. Personal communication.

Nagle, J. Stewart. 1997. Citrus for the Gulf Coast, A Guide for homeowners and gardeners. Forest of Treasures Press, Clear Lake Shores, Texas.

Royal Horticulture Color Chart. 2007. The Royal Horticulture Society, London, England.

Sauls, Julian W. 1981. Cold-Hardy Citrus. The Texas Horticulturist, Vol. 7, No. 3. 3 – 6.


Orange FrostT Hardy Satsuma; Citrus for the Home Garden
Beautiful, evergreen Orange Frost T Hardy Satsuma has fragrant flowers and golden-orange fruits and grows anywhere in the U.S as a patio plant in a large container.

Hardy Satsuma add both nutrition and beauty to the edible garden. These small, spreading evergreen trees are cold tolerant to 15 degrees F. and grow to about 10 feet tall by 8 feet wide.

The fruit on Orange FrostT Satsuma Mandarin Orange is a brilliant orange and contrasts well with glossy, dark evergreen foliage. Like other citrus, the white flowers in spring add a heady fragrance of orange blossoms, celebrated for centuries. There are many recipes that include the juicy, delicious, nearly-seedless and easy-peeling fruit.

While cold hardy only in subtropical regions (U.S.D.A. Zones 8B- 11), Orange FrostT Hardy Satsuma may be grown everywhere in large tubs that are brought indoors to a greenhouse or sunroom in colder climates for winter protection.

Wintertime is when the brilliant fruits ripen, creating a striking ornamental tree.

Orange FrostT Hardy Satsuma Mandarin Orange, Citrus reticulata 'Gremoy47'
Plant Category: Flowering and fruiting broadleaf evergreen citrus fruit tree
Mature Height: 8 - 12 feet; approximately 6 feet if container grown
Mature Spread: 8 feet ; approximately 5 feet if container grown
Mature Form: Small spreading tree
Growth Rate: Moderately vigorous
Sun Exposure: Best grown in full sun
Soil Type: Normal soil with average fertility.
Container Soils: May be grown in large tubs of moist, well drained potting mix with slow release fertilizer and trace elements. See:
Soil Moisture: Evenly moist, well-drained soils
Flower Color: Heavenly orange-blossom fragrance; petals white to ivory "orange blossoms" in terminal clusters bloom in spring
Fruit Set: Trees are self-fertile with low seed count, approx 1.3 seeds per fruit
Fruit Yield: Good yields; container-grown Satsumas will have several fruits per tree to brighten up a greenhouse, sunroom or enclosed porch.
Summer Color: Dark glossy green leaf color
Fall Color: Evergreen year round
pH Level: Adaptable
Zones: 8B - 11 subtropical, well-suited for container-culture across the U.S. with winter protection
Heredity: Developed by San Antonio Botanical Garden, Texas A&M AgriLife Extension horticulturists and Greenleaf Nursery Company/Texas

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