The mandarin orange tree (Citrus reticulata) is known for its small, sweet fruits, and the 'Clementine' variety (Citrus reticulata 'Clementine') is the smallest of the mandarin cultivars, with fruits often fewer than 2 1/2 inches in diameter.
'Clementine' is winter-hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11, which means it can be grown outdoors all year in Central and South Florida. In the Panhandle, the tree is more likely to do well when grown in a container and taken indoors for winter.
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Selecting a Site
Choose a site in your garden that is exposed to full, direct sunlight to grow 'Clementine' mandarin trees. They can tolerate some light shade but produce more fruits when they have plenty of access to sunshine.
Plant the trees in an area with well-drained soil; sandy soil works well. Citrus trees do not thrive in standing water, and they struggle when planted in soil that doesn't drain quickly and completely. If you want to plant 'Clementine' trees in containers, then fill the pots with a loose, well-draining potting mix, and ensure each container has holes in its bottom for drainage. Place only one tree in a pot. Young trees will do well in 3 gallon containers, but larger and more mature trees require larger containers approximately 5 to 7 gallons in size.
Plant the trees any time during the year, spacing them 15 feet apart. Make sure the planting area is free of weeds and sod. Planting in a site where sod or weeds butt against the trunk promote rot and fungal problems. Do not mulch around the tree and if planted in an area where mulch is installed, make sure the mulch is kept at least 1 foot away from the trunk.
Established 'Clementine' trees don't need much water, but young trees need consistent moisture. Water the trees twice each week for the first month after planting them, giving each 8 to 10 gallons of water every time you irrigate. After the first month, water less frequently, but irrigate whenever the trees' new growth begins to wilt.
'Clementine' trees need regular fertilization, and their fertilizer needs increase as the trees grow larger. Give each first-year tree 4/10 to 8/10 pound of a granular 6-6-6 fertilizer in each of six applications, applying the fertilizer every six weeks beginning when the tree's leaf buds start to swell in the early part of the growing season, typically in February, and ending in October. Increase the amount of fertilizer per application to 1 to 2 pounds for each tree in the second year, but decrease the number of applications to five.
Scatter the fertilizer on the soil surface around each tree, extending the radius of the application beyond the tree's drip line by 1 foot for each year of the tree's age.
Growing Them Indoors
In areas of Florida where frost is a possibility, take container-grown 'Clementine' trees indoors in fall before temperatures turn cool. Keep the container trees in a cool location near a window with a southern exposure. Use a spray bottle to mist their leaves daily. Move the potted trees back into the outdoor garden after all danger of frost has passed in spring.