Why You Want to Grow Citrus Grafted on Trifoliata

Poncirus Trifoliata (PT) is the best rootstock for growing citrus trees along the upper Texas Gulf coast, even into Louisiana.  PT is a three petal leafed citrus (see picture below) that was brought from China as a rootstock for citrus along the gulf coast.  It is the only citrus that loses it leaves in the winter and goes dormant.  It will not freeze.  Only way south in the Texas Rio Grande Valley, Florida, and soil flooded by salt water is PT not suited for growing citrus.  

When buying a citrus tree try to find out what is its rootstock.  If you can not find it on the plant label, check out where the originating nursery is located. (Some local nurseries buy from wholesellers in the Texas valley)  If it is located in the Texas valley, good chance it is grafted on sour orange.  My trees are labeled on what rootstock they are grafted.  Sour orange that is used for rootstock produces leaves with a single main petal attached at the base to a petiole (small petal) which in turn is connected to the stem.

Wild Poncirus Trifoliata.  Notice the 3 petal leaves.

PT's beneficial reasons are:
  1.  Citrus grafted on PT make a semi-dwarf tree about 8’ in diameter and about 8 to 10’ tall.
  2.  PT is resistant to phythoptera  (root rot).  Sour orange rootstock is not resistant.
  3.  PT goes dormant in the winter, so reduces the water flow to the scion and gives the scion a few degrees of cold protection.  Ice crystals are what ruptures the leaf and limb cells.
  4.  PT will not start growing and producing tender new growth with a few days of warm weather in the winter.
  5.  PT is immune to Tristeza virus, the sour orange tree killer in the Texas valley.
  6.  PT is a tough plant that has adapted to the upper Gulf Coast soils, is growing wild in the woods, and is resistant to soil diseases and neamtodes.
  7.  PT is compatible and can be used as a rootstock for almost all citrus varieties.

PT’s only draw backs are:
  1.  It can get Exocortis viroid from contaminated gardening tools.  (Sterilize your garden tools with 1 part bleach to 3 parts water before using on citrus).
  2.  It can not be grown where there are large amounts of salts in the soil.  (The valley people would love to use PT, if it were not for all the salts in their soil).