This post has been rumbling around in my head for quite some time. Citrus trees are among container gardeners’ favorite victims fruit trees, so I don’t know why it has taken me so long to put my thoughts down in a blog post. I have had several citrus trees, including blood oranges and tangerines. Though one of the professors that taught my master gardener class would disagree, they make great container plants. Here’s how to grow a little bit ‘o sunshine on your balcony or patio…
Suitably Small Varieties for Container Gardening
Like all trees you plan to grow in a pot, you should always, always, always select either a natural dwarf or a tree growing on dwarf rootstock. According to Sunset’s Western Garden Book of Edibles dwarf citrus trees are usually grafted on to one of two kinds of root stock. If given a large enough pot or grown in the ground, trifolate orange (Poncirus trifolate) will produce a 10 foot tree in 15 years, while ‘Flying Dragon’ trifolate orange produces an even shorter 7 foot tree in that time period. Either rootstock variety will sufficiently stunt the growth of your tree to make it happy to grow in a container.
Kumquats produce fruit that look like tiny, oblong oranges. They are usually tart, and the fruit is eaten skin and all. You don’t need to select a variety growing on dwarf rootstock because these citrus trees are naturally short. Kumquats do best in areas with warm summers and chilly fall/winter nights. They’re hardy down to 20F if the pot is protected. Kumquats can usually be brought indoors in cold winter climates and still produce a good harvest.
- ‘Fukushu’ produces sweeter-than-normal fruit and the tree is thornless
- ‘Meiwa’ is the sweetest, and least-seedy variety of kumquat. Trees are nearly thornless.
- ‘Tavares Limequat’ is a cross between a kumquat and a Mexican lime. The tree is attractive and compact (less than 6 feet tall at maturity)
Lemons are a great choice in areas with summers that aren’t hot enough for other types of citrus. They especially enjoy coastal areas, and will produce fruit year round near the beach.
- ‘Improved Meyer’ is the best variety for container gardeners. It is a disease-free version of regular ‘Meyer’ lemons (which cannot be sold in some states, due to the virus the trees carry). The fruit is sweeter with thinner skins thanks to the fact that is actually a lemon-orange hybrid. Can be brought indoors during the winter without sacrificing fruit production.
- ‘Sungold’ and ‘Variegated Pink’ both have green and yellow variegated leaves.
- ‘Gold Nugget’ was one of the favorites of the citrus expert from University of California that spoke to my master gardener class. It’s fruit is seedless, very sweet, and easy to peel.
- ‘Seedless Kishu’ was another favorite. The flavor of the fruit is very complex and delicious
Oranges need hot summers to produce sweet fruit, they do not do well in coastal areas or in northern climates with very mild summers.
- ‘Washington’ and ‘Robertson’ are nearly identical varieties of navel oranges. ‘Robertson’ produces fruit two weeks earlier than ‘Washington.’ Growing one of each prolongs your orange harvest.
- ‘Tarocco’ is a blood orange that has red flesh and a complex flavor with raspberry overtones. Makes an excellent espalier.
- ‘Trovita’ has thinner skin than navel oranges and has no navel. It also requires less heat than other types of oranges.
One Tree or Two?
Because fruit is the result of plant sex (I kid you not), many kinds of fruit trees produce the best harvest (fruit are the resulting offspring of the plant sex) when they have a similar type of tree near by to cross-pollinate. Most citrus varieties, however, are self-fertile. Which means they don’t need a partner to produce offspring. I’ll leave the weird mental images to your imagination, but this is good news for small-space gardeners because it means you don’t need to waste space with a second tree if one tree will produce all the fruit you need.
Choosing the Right Pot
Citrus trees need a pot that is at least 18 inches tall and wide. I have grown a dwarf mandarin in a pot that was not 18 inches wide, but it was stunted and fruit production was not as good. This is because citrus trees have roots that spread out close to the surface. In a citrus grove you’ll often find tree roots growing in the leaf liter below the tree. Select a pot with thick walls, glazed ceramic is ideal. I learned the hard way that citrus do not like the super-heated soil found in metal pots.
You’ll need to gently root-prune and repot every 5 years or so.
Watering Your Citrus Tree
You should water your tree often enough so that the soil only briefly dries out between watering. This may be every day in the summer. Withholding water for the week or two before you harvest will help sweeten the fruit.
Harvesting Your Fruit
You must, absolutely must, allow the fruit to ripen on the tree. To tell if the fruit is ripe, pick one and taste it. You can’t tell if the fruit is ripe by rind color, as most varieties color quite some time before they are ripe.
How to Prune Your Citrus Tree
Simply put, you don’t need to prune your tree at all. Pruning will not improve your harvest. Lower branches produce the most fruit, so definitely don’t cut those off. Prune lightly for aesthetic reasons and to remove any dead or diseased branches.
The What and When of Fertilizing
Nitrogen is your citrus tree’s best friend. Fertilize monthly from February to November with a high-nitrogen liquid fertilizer according to package instructions. In frost-prone climates start fertilizing later and stop earlier. If the leaves are deep green with burned tips, you’re fertilizing too much. Citrus are also very sensitive to soil that is too alkaline, a problem for those of us with hard water. If you see light green leaves with dark green veins, you most likely need to re-acidify your potting soil with some soil acidifier (sometimes marketed as a hydrangea blueing agent).