Growing Citrus Indoors

Having grown up in the frigid wilds of Wisconsin, my early experience with citrus had been limited to the magnificent sight of a field of blooming oranges trees that I once encountered in sunny Spain during a high school vacation, and of course the piles of oranges, lemons and grapefruit found in every grocery store. Then one day about ten years ago I made a trip to Logee's Greenhouses (see sources, below), and there came upon an ancient glass house filled with the most delicious scent: blossoming citrus. I decided on the spot that some of these plants were going home with me, and I selected two small specimens, an orange and a lime. Despite the assurance of the owner that once I started with citrus, I would be back for more, I was doubtful. Wasn’t it true that growing citrus indoors was fraught with problems? I fully anticipated that these two trees would prove to be difficult charges, and that, if they managed to survive the less than perfect conditions of my under-heated old house, they would most likely constitute the complete extent of my citrus growing experience. Not for the first time, I was wrong. A decade later, both trees are still going strong, having become the founding members of a rather large citrus collection now resident in the greenhouse. These various oranges, lemons and limes not only fill the space with wonderful scent most of the winter, but they also provide me with an abundance of fresh fruit. (As proof, I snapped the picture below in December, and the oranges you see hanging there were served fresh to the table for Christmas morning brunch.)

As I came to discover, members of the citrus family are quite easy to grow outside of the tropics, as long as you keep a few factors in mind. When growing citrus, location is everything. The plants must have a great deal of light -- full sun, in fact, most of the day. Anything less, and the bloom, if it occurs at all, will be meager and short-lived. (When happy, members of the citrus family are one of the few plants that bear both flowers and fruit simultaneously, providing their owners with a constant supply of both.

The second key factor is that the plants require a lot of humidity, (at least 50%) and should be kept on gravel trays full of water, or near a humidifier, during the driest winter months. Citrus also prefer to be kept a little cooler at night – between 50-60 degrees, with a rise into the seventies during the day. All this means that to grow citrus succesfully in the north, you need a bright, airy space akin to a greenhouse, such as a heated sun porch or solarium for the plants to winter in. (All citrus plants should summer outside after all danger of frost is past, and be brought back indoors before temperatures cool below 50 degrees.)

Finally, keep in mind that some varieties of citrus can grow quite large – so if space is a consideration, make sure to select dwarf or slow growing forms. Fortunately, to a great extent, the growth of even the larger varieties can be limited by not “potting up” – shifting to a larger pot each year as you normally would other plants; when pot bound, vertical growth seems to slow, while flower and fruit production is enhanced, as long as you remember to water and fertilize regularly.

So if like me, you live outside of semi-tropical climes where these beauties grace the outdoors, consider adding members of the citrus family to your indoor plant collection. I think you’ll find that reaching up to pick a fresh orange or grapefruit for your breakfast while snow covers the ground, is, well, in a word, truly sublime.

Citrus at a Glance

Sun: Full Sun

Temperature Range: days in the 70’s, night in the 60’s

Water: Citrus can not tolerate drought and must never be allowed to dry out; water whenever dry, but do not allow water to stand and accumulate in the saucer.

Fertilization: Citrus are heavy feeders and require regular doses of fertilizer throughout the year; I water mine weekly with a water soluble fertilizer.

Humidity: as much as possible, but at least 40-50%, which is a healthy range for both humans and plants in the winter.

Soil: General potting soil; plants can be allowed to become somewhat root bound.

Pest and Problems: Citrus are particularly susceptible to scale, aphids, mealy bug and white fly. Blackish, sticky soot which forms on the leaves is often the sign of these pests. Remove by hand, a strong stream of water, brush with rubbing alcohol, or other organic means. Do not use any chemical pesticides, especially systemic ones, if you intend on consuming the fruit. Placing your plants in the shower once a month for five minutes or so under cool water can mitigate most pest problems; just be sure to let the pot drain thoroughly before returning it to its place. Citrus can also suffer from a problem called chlorosis, which is an iron deficiency in the leaves; several products available at most garden centers will correct this problem.

Some Recommended Varieties:

	Citrus limon ‘Ponderosa’ "The American Wonder Lemon" White, fragrant flowers appear throughout the year with a particularly heavy surge in spring, and then the fruit appears. A favorite of my father who eats peals and eats them (!!!) these are not your run-of-the-mill grocery store lemons. Ponderosa lemons are capable of reaching enormous proportions, even though the plant remains an easily manageable size.
	Citrus limon ‘Meyer’ An heirloom dwarf lemon with delicious golden yellow fruit. It is the hardiest lemon for cool temperatures and makes a fine potted plant. The fruit is more flavorful than store bought lemons and it bears heavily at a young age. Makes a magnificent lemon meringue pie.
	Citrus aurantifolia ‘Persian lime’ "Tahitian Lime" Also known as the "Bears Lime," it is similar to the lemon in growth and habit. The fruit is medium-sized and relatively seedless. Vigorous and easily grown. Flowers and fruits year-round.
	X Citrofortunella mitis "Calamondin Orange" Renowned as a container-grown citrus, it’s a prolific producer of small edible oranges. Not only does the fruit hold well, adding to its ornamental value, but this famous hybrid displays an abundance of tiny fragrant flowers. A cross between a kumquat and an orange, the fruit is sour and often used in marmalades and Asian cuisine.
	Citrus myrtifolia "Myrtle Leaf Orange" This sour orange is one of the best citrus plants for containers because of its compact growing habit and hearty root structure. With densely foliated myrtle-like leaves, in spring it produces fragrant, white flowers and fruit that holds well for months. Pruning this enduring grower produces a well-shaped bush.

Sources: By far and away the best source I know for interesting citrus is Logees Greenhouses in Danielson, Connecticut. They have an extensive mailorder service, but if you are anywhere near the area, you really should stop in: the century-old greenhouse complex is a must-see for avid gardeners