GROWING CITRUS IN CONTAINERS
Producing Your Own Kumquats, Lemons, Limes, Mandarins, Yuzus, and Many More Inside and Out
As a California baby, I grew up with citrus. Literally; my grandparent’s garden, where I spent much of my time for many years, had a few trees in the ground. It was much later that I discovered the joy and ease of growing citrus in containers, even outside of California.
California certainly has the best climate for growing citrus, producing over 70 percent of the commercial U.S. crop, and hosts landscapes and gardens where citrus are regular features. Florida comes in second in production and gardeners there also enjoy the fruits of the labor involved in growing these shrubs and trees. In the southern parts of Texas and much of Arizona, combining for third place with just under 5 percent of the U.S. crop, citrus is fairly common in yards and landscapes. In Phoenix and a few other Arizona cities, citrus — specifically Seville orange (Citrus × aurantium; also called bitter orange, sour orange, and even marmalade orange) — are used as street trees.
A slight aside: During my first trip to Phoenix (1977?), while scouting for “garden stories” for a well-known magazine, the hosts treated me to a soda with a slice of Seville orange. The orange was used to cut the sweetness of the soda. And it did, fortunately — it was one of those soda brands that make the headlines in health reports, with 10 teaspoons of sugar per 12-ounce can. The sour orange didn’t make the sugar go away, but it did make the soda drinkable.
Even if you don’t have such idyllic climate conditions or if you have limited space (e.g., an apartment balcony), you can grow citrus. Just not outside in the ground. With a few exceptions (some oddball citrus types), citrus can survive only where temperatures never drop below 20°F and most are terribly unhappy even when temps drop below 40°F. The alternative is to grow citrus as semi-dwarf trees (on trifoliate orange or citrange rootstock) or as dwarf trees (on ‘Flying Dragon’ rootstock) planted in large pots on wheeled platforms. The semi-dwarf trees, which are more commonly available, require somewhat larger pots, of course, and a bit more care.
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THE CONTAINER
Plant new, small trees in a minimum of 12- to 14-inch wide containers. Starting with anything larger will make it more difficult to manage water levels and will waste water. Make sure the container has adequate drainage holes. The 12- to 14-inch container will hold your citrus for at least a year and probably two years. As the tree grows, increase the container size to 16 to 20 inches for the next 2 or 3 years of growth. Although ceramic, clay, and wooden containers are attractive, they are less mobile and more expensive than durable plastic; a consideration should either of those two factors be relevant.
There should be adequate drainage holes. Smaller containers are fine with one large hole (½-inch to 1-inch). Place a square of fine-mesh screening over the hole before you fill it; it will help keep out the larger insects, pillbugs, sowbugs, and slugs, who like to take shelter in the wet cavities. A large container should have 2 or 3 holes and up to 4 or 5 holes, with each hole ½ to 1 inch in diameter. I wouldn’t try to drill a hole or extra holes in a clay pot and drilling holes in a ceramic pot is a whole lot tricky. But if you have a plastic or wood container, and it needs a hole or extra holes, have at it. As the plant grows, increase the container size to 16 or 24 inches in diameter. That’s usually “the next size up,” but vigorously-growing citrus can safely go up two sizes.
You will need a saucer (preferably a deep one), of course, or, if and when outside, pot feet. Pot feet are shaped to fit under the bottom edge of the pot to hold the pot ½ to 1 inch above the floor. They provide air circulation below, minimize entry by tiny critters, and prevent staining of patios and decks.
Place gravel or decorative pebbles in the saucer to elevate pots above standing drainage water. The gravel/pebble layer can be kept nearly full with water to help raise humidity levels during winter when the plant is grown indoors.
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POTTING SOIL
Use a commercial OUTDOOR potting soil, which is heavier than indoor potting soil. Avoid potting mixes with fertilizers, peat, and wetting agents. I often add 1 part “calcined clay” to 4 or 5 parts potting soil to increase water-holding and nutrient-holding capacity. Calcined clay is the same as old-fashioned, unadulterated kitty litter or garage floor oil absorbing compound sold in hardware stores. It’s also available through specialty plant growers, especially bonsai specialists.
Do NOT use garden soil.
Do not put gravel or any other material (e.g., Styrofoam, plastic bottles, sticks and stones) at the bottom of the pot. It will negatively impact drainage in the long run. Fill the container from bottom to top with just potting soil.
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LOCATION, LOCATION, LOCATION
Because citrus are grown in greenhouses before retail sales, it almost always shocks the tree if it’s put into direct sunlight — whether indoors or outdoors — for too long the first week of planting or potting. The ideal location for the first week outside, with the plant still in its original container, is a spot by the house that has either indirect or dappled sunlight during the day or a spot by the house that gets no more than 2 or 3 hours of morning sun. After the first week, it can be moved to its final location, which ideally gets a minimum of 8 hours of full sun daily (almost sun-up to sundown), and then planted (in the ground or in the pot). You can expect new trees to drop some of their leaves during this transition period.
In marginally warm climates, select a site that gets reflected heat from sidewalks, houses, or walls on other structures. Also make sure the site is fairly wind free. In extremely warm zones, you will have to provide more consistent watering (citrus can handle temperatures over 100°F).
Potting up and placing a new plant indoors is even more unkind to the plant. Find a window with morning to midday sun; no more. Move it to a brighter spot in a week or two. Starting a plant in winter is especially difficult when it comes to adjustment. There will be leaf and flower drop. After a couple of weeks, you should be able to tell whether or not it is thriving or at least “settling in.”
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BASIC CARE
Citrus trees like moist soil overall with intermittent periods of dryness to help them stay at warmer temperatures. Water when the soil surface dries to about 1 to 2 inches down, depending on size of the container; deeper in really large containers. Actual watering frequency will vary with soil type, tree size, pot size, environmental factors, and phase of growth.
Always check the moisture level in the soil before watering. Use your finger to find where that moisture level is. Don’t let the pot go so dry that leaves wilt. Wilting indicates the root hairs have been lost and although the tree may perk up within 24 hours after a good watering, new root hairs must grow and that takes considerable energy on the plant’s part. On the other hand, a tree with yellowish or cupped leaves, or leaves that don’t look perky after watering can indicate too frequent watering that’s led to lost root hairs or even rotted roots.
When you do water, apply enough water so that excess runs out the bottom of the container (and, if indoors, into that saucer with gravel or decorative pebbles).
For outdoor containers, it’s best to water in the morning. But if plants are dry or, worse, wilted, water them right away, no matter the time.
Citrus should be out on the sunny patio or balcony all summer long (from late spring into earliest fall) in full, hot sun (sun-up to sundown). The less sun, the more the plant will develop a lankiness, the more it will struggle with excessive water, the less it will attract pollinators, and the more it will attract the very tiny insects that thrive where air circulation is poor: thrips, mites, whitefly, mealybug, and scale. If you plan on bringing such citrus into the house for winter, these pests, if you already have them, will then quickly go ballistic.
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AS INDOOR PLANTS
Citrus aren’t the easiest of indoor plants. But they are doable with a focus on these key care components:
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