Imagine: A hot summer’s day, a well-deserved break and you with a frosty glass of homemade lemonade from fruit you grew on your own patio! For the Northern gardener with tropical aspirations, this refreshing pipe dream can come true, courtesy of citrus plants grown in containers. These zesty little trees may start their lives as decorative houseplants in the winter and later as a focal point outside on the veranda. But with some attention and not an enormous amount of work, they soon will pay off in delicious fruit with a decidedly un-Northern sound to it: orange, lemon, lime, grapefruit, tangerine, sour orange and even more exotic treats like kumquat, limequat and tangelo. As a veteran container citrus grower, I can offer this advice: Decide what flavor you like, determine the fruit best suited to your own gardening style, then start digging. Once you succeed with one, plant another. But beware of the possibilities of a mini citrus plantation.
My collection of citrus plants began innocently enough with the adoption of my mother-in-law’s Meyer lemon (Citrus meyeri) plant. It wasn’t doing well indoors so I offered a spot in my greenhouse. Soon, with the added light and warmer temperatures, it began to flourish and put on new growth. When it suddenly produced intoxicatingly fragrant flowers, I was hooked. As fate would have it, not long afterward I had the opportunity to visit Well-Sweep Herb Farm in Port Murray, New Jersey. The owner, Cyrus Hyde, was most gracious and gave me a personal tour of his nursery.
As we entered his greenhouse, I was immediately struck with the impressive yet bizarre fruit of the citrus plant ‘Buddha’s Hand’ (C. medica). Imagine a fruit that is a bright canary yellow, in the shape of a hand with four fingers pointing downward. I had to have one. I was so excited by this citrus that I promptly collected more: Key or West Indian lime (C. aurantiifolia), Persian lime (C. aurantiifolia ‘Tahiti’) and Kaffir lime (C. hystrix). I figured if these could all be grown successfully in New Jersey, I would certainly have no trouble growing them when I returned to Oregon. I was right.
The genus Citrus comprises some 16 species and more than 100 varieties. It belongs to the Rutaceae, a family that includes the pungent rue plant. The genus consists of large evergreen shrubs or small trees (20 to 30 feet), often having stiff spines along the trunk and branches. Their attractive smooth, dark-green glossy leaves are simple and ovate. Both leaves and fruit are fragrant when bruised.
The true citrus have exceedingly popular edible fruit — called hesperidia — characterized by an outer rind copiously dotted with oil glands and inner segments filled with juicy pulp vesicles (tiny separate bags filled with juice). The large star-shaped, white flowers (either solitary or in small clusters of five) are usually exceedingly fragrant and are characterized by five fleshy petals with prominent stamens. Native to Southeast Asia and Eastern Pacific Islands, citrus is domesticated worldwide where climate permits.
Citrus require ample light, sufficient heat and fast drainage. It is important to realize that citrus plants have two major growth periods: one in early spring and another in mid-summer. During these two periods of growth, adequate water practices are essential and timely fertilization is important for the general health of the plant and for proper fruit development. I water thoroughly and allow the soil to dry just a little (no more than 3 inches deep in a container) before watering again. To avoid plant stress as much as possible, I avoid a “feast and famine” fertilizer approach by using a 9-month, slow-release fertilizer, which provides a constant feeding over the growth period. I try to use a high-nitrogen fertilizer, as equal or larger ratios of phosphorus and potash are not needed. (Osmocote fertilizer has the advantage of being temperature-released rather than water-released. This means as the temperature rises, the fertilizer is released when the plant needs it the most, when it is actively growing.) In winter, the plants require a dry dormancy to produce flowers. I water less and avoid fertilizing at this time.
Throughout the year, I look for iron and zinc deficiencies. Iron deficiency will show up in yellowing leaves with dark-green veins. Citrus plants need an application of these minor elements about every 2 months or so. However, overwatering will show the same symptom as iron deficiency. If the leaves show a general mottling or yellow blotching between the veins, then it is zinc deficiency. I treat the iron deficiency with chelated iron or iron sulphate. For ease of application I use Ironite, which is granulated. If it is a zinc deficiency, I use Lilly Miller’s Liquid Iron and Zinc plus chelates. I apply this as a foliar spray and continue every 10 days until it is cured. This has the advantage of treating both deficiencies but will stain clothing or concrete.
Temperature is a major factor in growing citrus plants successfully. They are hardy only where the winter temperatures are above 20 degrees. Therefore, I overwinter my plants in my heated greenhouse. And without sufficient summer heat during the fruit development period, they may not mature properly or may even cause premature fruit drop (at temperatures below 40 degrees). To ensure success in my Northern climate, I grow only lemon and lime citrus, as they require less heat than oranges to grow and produce fruit. Also, since orange citrus are generally trees, I find the smaller limes and lemons are better candidates for container growing — especially now when more than 30 cultivars are grafted onto dwarf rootstock and available commercially.
Fruiting and flowering occur simultaneously. This increases the time period of harvest but unfortunately it takes the fruit some three to four months to ripen. To harvest, I feel the fruit for weight and judge its color to indicate its maturity or ripeness. Some ripened fruit stays on the plant for several months so it is not uncommon that I am picking lemons or limes in the greenhouse in late winter or early spring.
Container-grown citrus are fun as well as highly decorative. More importantly, containers have the advantage of being mobile, either to meet light, heat and moisture requirements or for design purposes when you want a patio accent or garden focal point. I place the citrus in the warmest, most wind-protected part of the garden to ensure the highest temperatures for it to flower and fruit. Also, I bring it back indoors when there is a threat of frost or winter temperatures.
Except for vigilant watering, container growing is quite easy. I use clay pots, as they will evaporate any excess water in the soil. I find citrus plants, when slightly root bound, tend to flower sooner and fruit better. I don’t repot until every third or fourth year. I try to eventually reach a pot diameter of at least 18 inches across, which allows a soil volume sufficiently large enough to accommodate most of my specimens. After the weather has settled and night temperatures are consistently above 55 degrees, I place my plants outside. At this time, I also apply 2 to 3 inches of organic mulch to maintain even soil moisture and to act as a weed barrier.
Scale, mealy bug (which looks like small bits of cotton) and spider mites are the more common pests of citrus, but I find good cultural practices greatly benefit a plant’s overall health and make pests less of a problem. Spraying both sides of the leaves with horticultural oils in the spring kills scale and mealy bug, and periodic sprays with water keep down or even prevent mite infestations. If the mites do get out of hand, I prefer to treat with predatory mites rather than spraying a pesticide on something I may eventually want to eat.
For a fun children’s project, try germinating seeds from fruit. They will germinate easily. However, it will take years for them to flower and fruit. Stem cuttings that are semi-hard wood will root easily when taken in spring or summer. Beware of cuttings from understock or rootstock. I took some from a grafted plant, and the result was a much larger citrus with 2-inch sharp spines.
If you want a dwarf variety, I recommend just purchasing the grafted plant at a nursery. Growers have selected certain understock material for many good reasons: dwarf size, plant vigor, early fruiting and disease resistance. Also available at nurseries are citrus plants trained into single stemmed standards, which are quite attractive in a patio or courtyard setting.
Citrus Cultivars for Containers
Here in my Oregon greenhouse, I have collected a modest array of lime and lemon plants suitable for my growing conditions. Generally, they are all suited to container growing because they flower and fruit through most of the year.
Andrew Van Hevelingen is a frequent contributor to The Herb Companion and enjoys writing, photography and gardening in his Newberg, Oregon, home.