Growing your own citrus fruit is potential if you reside in a climate. In colder areas, you have to grow citrus in a greenhouse during cold months or move container plants inside your house when frost threatens. Planting grafted trees pushes the envelope on cold hardiness, but presents thorny obstacles that may grow beneath the graft union.
Even the most cold-hardy citrus trees endure frost damage, which may happen when temperatures reach 29 degrees Fahrenheit for just 30 minutes. A few lemon (Citrus limon), lime (C. aurantifolia) and orange trees (C. sinensis) naturally have thorns that grow regardless of that rootstock is used for grafting. For instance, of both main lemon cultivars, “Eureka” is almost thornless, while “Lisbon” contains thorns. Most citrus rootstock used for grafting contains thorns, making harvesting fruits a bit more precarious when a thorny scion or grass is grafted onto it.
To spread citrus trees, horticulturists use grafting or budding techniques instead of sowing seeds. Although a seed in the store-bought citrus fruit will likely sprout and grow, you will need to wait around 15 years for the resulting tree to bear fruit, depending on species. All commercially accessible citrus trees are grafted or budded to speed up the practice of harvesting fruit and also to increase disease resistance through using a hardier rootstock. Grafting takes the roots of a single plant, known as the inventory, and fuses onto it the take of another plant, known as the scion. Budding employs one vegetative bud in lieu of an entire shoot to splice onto the stock. Though some citrus trees are grafted, most are budded.
Grafted citrus trees have the best of both worlds — a scion or grass that’s chosen for its superior fruit quality, and a rootstock which has higher disease and pest resistance. Trees can also be bred to have after blossom times in order that they can avoid injury from late frosts. While sweet orange trees really are can withstand temperatures to 20 degrees Fahrenheit without sustaining damage, trifoliate oranges are hardy to minus 10 degrees. Trifoliate orange is one of few citrus trees which demonstrate resistance to foot rot, which is a disease that infects other varieties.
Trifoliate orange (Poncirus trifoliata) is a member of the citrus family Rutaceae. Trifoliate describes its leaflets of 3 leaves. This tree contains such formidable thorns which Dr. Hugh Conlon, retired extension horticulturist, calls it “the barbed wire of the plant world .” Also called bitter or hardy orange, trifoliate is frequently planted as an impenetrable hedge. Though it also bears fruit, they’re seedy and sour tasting. Its finest commercial value lies in the hardiness of its roots, making it a preferred rootstock for grafting sweet orange trees. Its thorns, however, will continue to grow below a graft union or grass, even on citrus trees which don’t normally bear thorns.