Kumquat

Citrus greening (Huanglongbing, HLB) is a bacterial disease with no cure -- infected trees are usually destroyed once unproductive (UF/IFAS Gardening Solutions). It is established in Florida, Georgia, Puerto Rico, the US Virgin Islands, and parts of Alabama, California, Louisiana, South Carolina, and Texas (USDA APHIS). Federal and state rules restrict moving citrus plants, plant parts, or homegrown fruit out of quarantined areas; USDA APHIS advises against mailing or transporting home-grown citrus fruit or plants out of a quarantined area. A USDA APHIS blog post (Aug 25, 2014) put the penalty for knowingly buying citrus trees in violation of quarantine rules at $1,100 to $60,000 per violation -- a federal figure, stated per violation, from a 2014 post (12 years old as of this writing), not a blanket "Florida penalty" figure and not verified current. Florida law (Statute Sec. 581.1843) requires citrus nursery stock be produced in an approved protective structure; UF/IFAS Extension advises buying only disease-free certified trees grown under the Florida Budwood Certification Program's rules. California has its own HLB quarantine zones with similar movement restrictions. Bottom line for a home grower: buy only from a certified/reputable nursery, and don't move a citrus tree, its parts, or homegrown fruit across a quarantine boundary -- check current boundaries with your state's department of agriculture before moving anything, since exact zones change over time and were unconfirmed for real-time accuracy.