In Bennett, Co., Bob Koch grows citrus in a greenhouse once devoted to starting seedlings for his commercial farm. Today the 32- x 72-foot structure houses 125 potted citrus of "every type you can think of" and two trees in the ground.
Citrus orchards are a lot of work. They need warmth and take ground away from other crops. What if you had a small one that you could protect from the cold, and put anywhere you wanted? Koch has discovered the secret: Subtropical citrus is perfect to grow in containers that can yield up to a bushel of fruit from each potted tree. Not only that, the fruit keeps on the tree for weeks without losing quality.
Koch, who started his hobby about 10 years ago, says, "I don't know a single person who did not kill his first citrus tree. The No. 1 killer of containers citrus is overwatering.
If I could only say one thing about citrus it is that it needs very good, fast drainage." To this end, Koch makes his own potting mix with four parts coconut husk and one part peatmoss. He also likes RootMaker and RootBuilder containers that are designed to encourage a full, well-branched root system and prevent circular growth of roots.
GO BEYOND ORANGES. Arlie Powell, a citrus aficionado and retired professor of fruit crops at Auburn University, teaches workshops on home citrus growing at Petals from the Past nursery in Jemison, Ala. His advice is to think beyond standard citrus fruits and look at some hardier varieties that work well in pots.
One of the most widely grown hardy citrus is calamondin, a hybrid of sour mandarin and kumquat. "What you can do with a lemon, you can with this," says Powell, "including making calamondin-ade and cutting it into wedges for tea." The tree takes temperatures down into the 20s, so you can leave it outside for most of the year in the South.
Powell also likes kumquats, which ripen from November to January and keep on the tree very well. Meiwa is a sweet variety, while Nagami has very tart flesh. To experience a fresh kumquat properly you must eat the whole thing, peel and all! The peel of both varieties is surprisingly sweet.
Another recommendation is Meyer lemon, a hybrid between a lemon and an orange; it is larger than a lemon and goes from green to a rich deep yellow-orange color.
The flavor is tart, but a little sweeter than typical lemons, making it a prized juice for seasoning and drinks. It bears in fall and often continues through winter and into spring.
There's nothing wrong with oranges, though—and there are hardy varieties. Powell recommends a red navel called Cara-Cara that develops a beautiful reddish-pink flesh. The flesh of European blood oranges like Moro won't color well unless the night temperatures are in the 60s or lower when they ripen.
Most of the plants above are safe until temperatures reach the low 20s— some even the teens—but like most plants, how much cold a tree can take also depends on whether or not it has been gradually hardened off.
WARM THE ROOTS.One quirk of growing citrus in his cold climate has to do with root temperatures in winter. "Fifty-five degrees is absolute zero for the function of citrus roots," says Koch.
During the winter some people put their tree by a window in a chilly room; the sun shines through the glass and warms the leaves, but the soil in the container is cold. "Then the roots can't get moisture up to the tree and you get leaf drop—a big problem with indoor citrus," says Koch. "Keep the root temperature no lower than 64 degrees."
See next page for more information on growing citrus in containers or in the ground and how to buy.
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Container Citrus FAQ
WHAT SIZE POT? Pot citrus trees in at least a 10-gallon container; as plants get bigger they will yield more if you step them up to 15- to 25-gallon size. A satsuma in a 25-gallon container (one-half a whiskey barrel) will produce up to a bushel a year. A whiskey barrel half is about 25 gallons. You can use a nursery liner and put it in a decorative pot to place indoors. If you buy a 3-gallon tree, start it directly in a 15- to 25-gallon container. It will fill the pot in three to four years.
WHEN DO YOU REPOT? The plant will ultimately get to a point where it stops growing or even declining. At this point move it up to a larger container or prune the top. You can root prune, too, but not heavily.
Citrus develops very fine feeder roots (visible at the top of the root ball) so it acclimates to growing in a small space. You can compensate by pruning the top a bit.
WHAT ABOUT WINTER PROTECTION? In areas that don't dip to the single digits, you can keep a big plant on a dolly on the south side of the house, ideally protected by an overhang. When a freeze is predicted, you can protect the tree by enclosing it with a polypropylene freeze cover and put 15- to 30-gallon containers of water inside the wrap to help hold heat.
WHAT POTTING SOIL? Buy professional-quality potting mix that drains well. Both the soil and pot must have excellent drainage.
WHAT ABOUT FERTILIZER? Use a specialty citrus food that contains iron and other micronutrients.
Cold-Hardy Trees in the Ground
Thanks to the efforts of Southern citrus enthusiasts, extra cold-hardy citrus trees are growing in the ground at least as far north as Aiken, S.C., and Jemison, Ala. Some are varieties from Asia; others are old ones that survived freezes in a process of natural selection until only the hardiest strain remained.
They include names like Yuzu, Ten Degree tangerine, Kimbrough satsuma, Changsha mandarin, and Thomasville citrangequat. Some are recorded to survive temperatures in the teens or single digits. Generally, the more hardy the fruit, the less desirable the flavor, but breeders are working to change that.
In Scranton, S.C., Stanley McKenzie just planted an acre of satsumas to begin a citrus U-pick. "I've been dabbling in citrus since the 1980s. When folks first tasted the fruit off my trees, I must have had a hundred people wanting them. Having grown up on the farm I saw an opportunity here."
Squarely in USDA Zone 8, lows in Scranton dip into the mid-teens a couple of times each winter. Each tree has a sprinkler system prepared to protect them the way growers do in north Florida, if needed. Will it work? "I'll know next spring," says McKenzie, who is known in these parts as Stan "the Citrus Man" McKenzie and for T-shirts that say, "Orange you growing citrus?"
How To Buy Citrus
Most citrus plants are budded or grafted onto a compatible, hardy rootstock (except lemons and limes, which are often grown from rooted cuttings).
For containers, Powell recommends plants grafted on Flying Dragon (a dwarfing rootstock) for satsumas and most other citrus except kumquat or other types that are naturally small.
You may find these plants at your local co-op or garden center, or you can order them by mail (often described as dwarf citrus).
Read shipping restrictions carefully because regulations limit or prevent shipping into Florida, Alabama, Louisiana, Texas, Arizona and California—the citrus producing states; you should be able to find them locally there anyway.
Again, if you are buying for containers, check the rootstock before you buy. Beware that some retail sources, especially big-box stores, may not use the dwarfing rootstock because it is slow to grow. If in doubt, opt out.