Citrus provide an excellent source of winter fruit, high in vitamin C and minerals. Cold hardy citrus can be grown in climate zones 14, 4 and 15 in the Klamath-Trinity region, as well as the milder areas of zone 7. These areas all have plenty of heat to ripen the fruit, the real trick is protecting the plants from hard winter frosts, and even then you’ll have to live with the occasional severe cold snap that may destroy a crop and/ or lightly damage foliage. Citrus require a fertile, well-drained soil and nitrogen throughout the growing season – start applying in late winter and stop late summer to avoid promoting tender, first prone growth late in the season. Citrus require minimal pruning, shaping the tree and removing old and dead branches is usually adequate. Rolling River Nursery is local nursery that carries a wide selection of cold hardy citrus.
Variety Selection – Stick to the most cold-hardy citrus varieties for the best chance of success such as kumquat, mandarin Meyer lemon and calamondin
Site Selection – Planting in a greenhouse will ensure the best frost protection, you’ll need a larger walk-in greenhouse rather than a cold frame, and it’s best to have side walls that can be raised for summer ventilation. Even greenhouse planted citrus will experience occasional frost damage during our coldest spells. Growing outdoors is limited to zone 14 and banana belts, look for south facing walls, overhangs, and thermal mass. See Microclimates for more detail. It’s also possible to grow citrus in containers.
Frost Protection – Be prepared to provide supplemental first protection during the coldest weather. This includes covering plants with row cover fabric and/ or stringing Christmas lights in the tree (use the older type, the energy efficient LED lights do not produce enough heat). Deep mulching helps to protect the shallow root systems.
Meyer lemon - Though not a true lemon, it looks and tastes exactly like a lemon with the advantage of being sweeter and more cold -hardy. The thin-skinned, juicy fruit hangs well on the tree for an extended harvest through the winter. The mild flavored rind can be grated or eaten with a bit of honey.
Kumquat – A small, orange colored fruit, unique among citrus in that the tender flesh is sweet-tart and the fruit is eaten whole.
Mandarin – Delicious, thin-skinned fruits that peel easily and have a unique flavor and extended harvest. One of the largest groups of citrus that includes many named varieties. Satsuma is one of the more old-hardy varieties that do well in the Klamath-Trinity.