Citrus – Hardy Orange

October 9, 2020 – An Interesting Help Desk Citrus question answered by Ann Wagner 2016 Certified Master Gardener.

This article pertains to a citrus call received at the Master Gardener help desk. It is worthy of an article because of the nature of the call–a prolific citrus tree in a yard across from Mary Hardin Baylor. The call came in on October 9th and the caller was concerned about imperfections on the peels of his prolific lime trees and something not right with the taste of his limes.

Being a graduate of University of Florida and having taken numerous citrus courses I thought it very unusual for there to be a fifteen foot tall lime tree in Bell County Texas. Upon returning the call the property owner agreed to a site visit. I found there were two trees, which were full of citrus fruit and indeed about fifteen feet tall. They looked healthy. They did look like limes until I noticed two characteristics which were not present in the photos we received.

The citrus trees had numerous long spikes on the branches and a fruit that had been on the ground was yellow orange and the leaves on this citrus were shedding. These were all things that I observed and are indicative of Trifoliate Orange or Hardy Orange It is the only citrus tree that loses its leaves in the Fall. After we cut open the fruit , I saw that these were not limes, but rather Poncirus Trifoliata which is the scientific name. The fruit pulp did not look green enough to be a lime, it did not smell like lime or lemon and the taste was terrible. There were about 10 large seeds in each fruit. The leaves were compound with winged petioles. .Having seen these growing on the University of Florida campus as well as growing wild in the wetlands around Nacogdoches, Texas where I was a Soil Conservationist; I was able to deduct that these were indeed Trifoliate Orange or Hardy Orange. Strange enough, Trifoliate Orange is not used for its fruit and it is too thorny to grow around pets or people, so why this man had two of these originally bought from Lowes seven years ago is still a mystery.

In the citrus industry, Trifoliate Orange is used as a rootstock for orange and grapefruit to make them cold hardy . The rootstock is cold hardy down to sub zero and has been cultivated for thousands of years from Northern China to Korea. It was introduced in the US during Colonial times for livestock fencing due to its large thorns. What I find interesting about this site visit in Belton is how these two trees are growing so well in soil that is most likely alkaline. The Texas ArgiLife Extension website states that the Trifoliate Orange does not do well in alkaline or saline soils.

After doing additional research on the Hardy Orange on the North Carolina State University Extension site (https://plants.ces.ncsu.edu), I learned it is considered somewhat invasive due to its prolific fruits which produce many large seeds which birds disperse. It grows best in acidic soils and in hardiness zones 5 to 9.