Growing Dwarf Citrus in Containers
By Bob Chapman
The weather is warm, the wind calm and you are sitting in a comfortable chair on your patio. To your right is a dwarf Washington navel orange displaying the bright color of its ripe fruit. Temptation is overwhelming and you get up, get a pair of pruners and snip off one orange. Languidly peeling it and eating a section at a time, you realize that it can't get much better than this!
You can have success in growing dwarf citrus in containers. Here are a few suggestions for accomplishing this.
Containers
Containers are available in a wide range of large plastic pots or the familiar redwood boxes. Dwarf citrus will grow equally well in either.
Hardiness
In most of our mild winter areas we can grow dwarf citrus without concern about the weather. All citrus prefer growing in full sunshine. Oranges, lemons, grapefruit, some varieties of limes, kumquats, Satsuma mandarins and calamondins grow nicely where the summers are hot and the winters are mild. In areas that are freeze-prone, protection will have to be given in the winter.
Watering your dwarf citrus in containers
It is said that 50% of the troubles growing dwarf citrus in containers is found in the watering practices. Your dwarf citrus must have the right amount of water at the right time. When do you need to water? When the soil at the surface is dry. How do you tell if it is dry? Use the "finger test" or a moisture meter. Stick your finger into the soil and if it comes out with no soil particles clinging to it, then add enough water to wet the soil in the container all the way to the bottom. A more sure method is to use an inexpensive (under $8) moisture meter. Simply insert the probe of the meter into the soil and read the amount of moisture. It can't get much easier.
Consider using a simple drip watering system. Connected to a timer, these systems give your container(s) water periodically. You can adjust the time and the amount of water given easily, thus ensuring happy citrus. A free installation guide produced by Raindrip is available in the plumbing department of our stores.
Fertilizing dwarf citrus
Citrus prefer a regular, almost continuous supply of nutrients for best growing conditions. One way to do this is sprinkling a very small amount (a couple teaspoonfuls) of Superfine Lawn Fertilizer over the surface of the soil every other week and watering it in. This fertilizer contains all the major and minor nutrients your citrus needs. Citrus suffer from a shortage of iron and nitrogen, reflected in discolored leaves.
Pruning dwarf citrus
Do most of your pruning to keep your tree in bounds in summer, fall or winter. Oranges need little pruning, usually to cut off any deadwood inside the tree. Oranges like to have their foliage down to the rim of the container. Lemons grow more vigorously, sending up and out and often wayward shoots. Unless needed to shape the tree they can be removed. Other common citrus will need only occasional grooming to retain their shape.
Harvesting your citrus
Color can sometimes fool you. The best way to tell if the fruit is ready for picking is by tasting it. Use pruning shears to cut off the fruit instead of pulling it off. Harvest what you need, when you need it. Lemons and oranges can be "stored" on the tree until needed. Oranges, especially, will keep this way for several months after ripening. They lose a little of their sugars, but not too much.
Sweetness of the fruit
There is no way to increase the sugar content of citrus. Heat in the previous summer is the governing factor. Citrus grown in coastal environments may never develop enough sugar to match store-bought fruit. Most citrus, especially grapefruit, need very hot summers to have sweet fruit the next season. Lemons will ripen with the least amount of heat.
Transplanting
After a few years your dwarf citrus may outgrow the container it is in. Transplant it to a new container at least two inches or more wider than the previous one. It will probably take two to do this task. After removing your citrus from the old container use a utility knife (with its very sharp razor blade) to cut a quarter to one-half-inch-deep slit from top to bottom in several places around the perimeter of the root ball, cutting off the encircling roots. New roots will form and spread into the new soil. Allow about an inch space between the top of the root ball and the top of the container. Use OSH Premium Potting Mix when transplanting to your new container. This specialized mix contains polymers to help retain moisture and allow air to reach the roots. While adding the potting mix, press it firmly around the edges and down into the bottom of the new container to eliminate air pockets. Water your citrus thoroughly after transplanting.
COMMON CITRUS PROBLEMS AND SUGGESTED CURES
Chlorotic leaves. Yellowing leaves can be a symptom of a deficiency in one or more micronutrients (iron, manganese or zinc), or poor drainage. To correct any noted nutrient imbalances, spray the tree with a liquid fertilizer containing these micronutrients, such as Miracle-Gro, when the leaves are young, soft, and not fully expanded.
Insect pests. Hosing off the tree occasionally with a strong jet of water will help control most insects bothering citrus. The trees natural predators will help control invasions of aphids, whitefly, mealybug and scale. Ants, however, "farm" these sucking insects, using excess exudate, called "honeydew," as a food source. Keep ants out of the trees by banding the trunk with masking tape and then covering this with Tanglefoot, following directions on the container. Severe infestations of insects can be controlled with horticultural oil, insecticidal soap, or malathion. Read and follow directions on the container for best results.
No fruit setting, excess dropping of small fruits or thin crop. Many citrus bear heavily in alternate years. Thinning the fruit in the heavy production years tells the tree to produce fruit the following season. Citrus will undergo "self-thinning" when the fruits are about pea-sized. The prodigious amount of flowers will set more fruit than the tree can handle and it drops the excess. This condition is known as "June Drop" and it often happens during the first heat wave of the season.
Holes in the leaves. Snails love citrus trees and may stay in a tree for many weeks, eating merrily away. Prevent snails from climbing by placing a copper collar around the trunk and by regular baiting or trapping.
Fruit splitting. When winter rains coincide with the fruit ripening, there may too much water absorbed, causing the fruit to swell and crack. Also, cracking can occur if the tree is stressed from a lack of water and then watered heavily. You can't control the rainfall but you can ensure regular watering.
Sooty Mold. This blackish stuff is a fungus that grows on the honeydew excreted by insects. While not harming the leaves directly, it can prevent light from reaching the leaf surface, causing the leaf to produce less food and to turn yellowish. Prevent sooty mold by controlling the insects that excrete the honeydew and preventing ants from accessing the tree. Sooty mold can sometimes be hosed off or is washed off by winter rains.
Portability of container–grown citrus
Placing wheeled dollies under the containers affords the luxury of moving your trees and placing them to their best advantage on the deck or patio. Thus you can take advantage of a tree loaded with colorful fruit or when the tree is covered with fragrant blooms, bringing them out where they can be enjoyed and admired by all that see them.
Protecting redwood decks
Placing 1"X 1" strips of wood between the bottom of the container and the deck allows air under the container and avoids the possibility of the continually moist conditions causing the rotting of the deck.