June 02, 2010

Satsuma Miho mandarins tolerate 14 degrees Fahrenheit

New Texas Superstar is a patio orange without the pathos

By: Robert Burns, 903-834-6191  
Contact(s): Dr. Larry Stein, 830-278-9151, larrystein@tamu.edu  
COLLEGE STATION - - Not to be uppity, but just because a plant is favored by oriental royalty doesn't necessarily mean it's good enough to be a Texas Superstar, said a Texas AgriLife Extension Service expert.

Satsuma Miho mandarins are one of the five new Texas Superstars for 2010, said Dr. Larry Stein, AgriLife Extension horticulturist. After rigorous testing, horticulturists with Texas AgriLife Research and AgriLife Extension designate plants as Texas Superstars that are not just beautiful but perform well for Texas consumers and growers.

"They're highly prized in Japan," Stein said. "But we were looking for a more cold hardy variety with very good quality."

Many satsuma mandarin varieties do well under Texas conditions, and satsumas were promoted as Texas Superstars as a group in 1993."

"But we never promoted a specific variety, not until now," he said.

What changed Satsuma Miho's status? Years of further testing, Stein said. The previous recommendations for satsumas, at least as container plants or patio plants, was that they be brought indoors if temperatures threatened to drop below 25 degrees Fahrenheit,which is still a good idea for the first few years of the tree's life. Also, many of the satsumas required being grafted onto a hardier rootstock, and the Texas Superstar team wanted something easier to grow.

In 1994, AgriLife Extension and AgriLife Research horticulturists planted several satsuma varieties – Miho, Seto, Okistu and Kimbrough – under identical conditions at the Texas AgriLife Research and Extension Center at Uvalde. They used two-year-old container-grown plants that had either been grown on their own roots or grafted to sour orange rootstock.

For winters of 1996 and 1997, the trees were protected from freezing temperatures using dry cedar mulch.

"The entire trees were covered these two years," Stein said.

In 1998, to test cold-hardiness, the trees were left uncovered and a low of -8.9 Celsius (about 16 degrees Fahrenheit) was recorded. Stein said the trees lost some leaves but for the most part, their wood was undamaged.

In January 1999, temperatures dropped to -6.9 Celsius (about 20 degrees Fahrenheit) and again there was no damage to the wood.

Both the Seto and Miho produced high quality fruit, but the team eventually chose Miho as a 2010 Texas Superstar.

"Not only was it a very high quality fruit, but it also rooted quite readily from cuttings," Stein said. "It tends to root best and grow off best (of any of the tested varieties.)"

Mature budded Miho trees are small to medium size, from about 10-12 feet tall with a spread of from 13-15 feet wide. Trees grown on their own roots are generally about two-thirds the size of budded trees, he said.

"The color of Miho fruit develops in late summer and early fall; the peel is smooth and thin and leathery," Stein and his colleague, Dr. Jerry Parsons, retired AgriLife Extension horticulturist, wrote in their official report. "Fruit has been allowed to hang until early December ... but should be harvested around or just before Thanksgiving. "

Though Satsuma Miho is technically a small tree, it can be grown in a container. The tree's size is further dwarfed when it is containerized, Stein said.

He also noted that many people lose their patio citrus trees in the first or second year of the tree's life, and though larger trees have withstood temperatures in the teens without damage, it's a good idea to roll the containerized tree indoors when temperatures are apt to drop to 25 degrees or below.

More information on the history, care, propagation of Satsuma Miho and other patio citrus varieties can be found at http://aggie-horticulture.tamu.edu/patiocitrus/.

Texas Superstar is a registered trademark owned by Texas AgriLife Research, an agency of the Texas A&M System.

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