Ask Mr. Smarty Plants

We assume MDOT means Mississippi Department of Transportation, and a highway is coming through your mother's garden, for which we are very sorry. The Psidium guajava, Guava is native to southern Mexico, the Caribbean, Central and South America. The Lady Bird Johnson Wildflower Center is dedicated to the growth, protection and propagation of plants native not only to North America but to the areas in which those plants grow natively. This USDA Plant Profile shows that the Guava is recorded as growing in Louisiana and Florida and, obviously, we are sure it will grow in Mississippi as well. This plant is a member of the Myricaceae family, which also includes Morella cerifera (Wax myrtle),  a shrub which is native to New Jersey west to Eastern Oklahoma and Central Texas. Since we can find no specific information on transplanting a guava, here is some information on propagating or transplanting the wax myrtle:

"Transplants can be made bare-root in the wintertime (USDA-NRCS & USDI-NPS, 1993), or balled and burlap plants can be transplanted in the warmer months if the location is shady and the soil is kept moist (Nokes, 1986). Small plants have been successfully transplanted from containers in early spring. Use of a rooting hormone is recommended with bare-root plantings (Nokes, 1986). The use of plastic plant shelters is beneficial to protect young plants from heavy browsing, reduce plant competition, and create a friendlier microclimate until the young plant can get established."

Remember, this is talking about a wax myrtle, not a guava, and we really don't know if the same instructions apply. The size of the plant and especially the rootball are going to be determinants in how well the plant will transplant, no matter what. We would suggest you get a licensed professional arborist to make recommendations about whether it is better to try to transplant the trees, or leave them to the bulldozers and plant new small trees actually native to the area.