Citrus Container Takeaways:

1. Container gardening makes growing citrus possible anywhere in the US
2. Drainage is of paramount importance, make sure your container has adequate holes if it isn’t a mesh/fabric type pot.
3. We recommend a 15-gallon pot as the ideal size, with fabric pots having significant advantages.
4. Do not purchase a pot whose mouth is narrower than its body.
5. Every 4-5 years, your citrus tree will likely need to be re-potted
6. With micro-budded citrus trees, there is no need to “build-up” to a 15-gallon by transplanting into gradually larger containers, just plant straight into a 15-gallon container.

The Benefits of Containers for Growing Citrus

Container plants afford homeowners the flexibility to move the plant to locations in which the plant can obtain suitable moisture and sunlight to encourage growth. Additionally, the flexibility also allows homeowners to move plants indoors to protect the plant from harsh winter conditions leading to chilling injury or plant death.

As a result, growing container plants allow homeowners to grow plants that are exotic to their area. Several factors have to be taken into consideration when deciding to grow container plants. Factors such as light, water, temperature, air movement, relative humidity, and the growing container itself.

The Important of an Adequate Growing Container

The purpose of this article is to cover the importance of selecting an adequate container, particularly for growing citrus, like Meyer lemon trees, Australian finger lime, Kaffir or Persian lime trees, Navel or Blood or Valencia or Pineapple orange trees, Rio Red Grapefruit trees, Kumquat trees, or Calamondin trees.

Container Citrus History

The current trend of growing container citrus is actually an old practice that was reserved for wealthy homes in the use up until the 1930’s. King Louie XIV of France grew citrus in Orangeries at the Palace of Versailles, which are still in existence. Furthermore, citrus trees were grown on ships during long expeditions to help prevent scurvy ¹. With this in mind, it is very feasible to grow vigorous, healthy, and beautiful container citrus, with the proper care.

Not all citrus plants are created equal. As such, when choosing the type of container for your citrus tree, you have to consider the growth parameters for the specific cultivar you plant on growing. Factors such as container material, weight, color, drainage, and size all play an important role in the overall health of your tree. Let’s begin with the type of material that make up the various type of containers commonly used to grow plants.

Container Types & Material for Growing Citrus

There are three major container types, nonporous (plastic, metal, fiberglass glazed ceramic), semi-porous (wood) and porous (clay, unglazed ceramic, terracotta, and mesh/fabric)². Citrus can be grown in any of these containers but there are advantages and disadvantages to all, concerning the type of trees, water scheduling, and general environment in which the plant will be grown in.

For example, nonporous pots keep moisture better than semi and porous containers, so the plant would have to be watered less frequently. Concerning unglazed ceramic pots, these should not be utilized if your trees will remain outdoors during the winter, due to the absorption of moisture leading to the freezing and cracking of pots.

Soil Temperatures

Soil temperatures can fluctuate greatly between night and day in containers. As such, the use of metal containers as pots may exacerbate this effect leading to poor plant growth. Wood containers have great curb appeal. A high-quality cedar or redwood pot can last for many years, but lower quality wooden pots are prone to decay.

In general, you should consider that a wooden container will need to be replaced with the plant re-potted every 5 years or so because of decay of the wood from water exposure. Plastic containers have the advantage of retaining moisture well, but if exposed to sunlight for prolonged periods of time the color of the pot may fade, and black pots will create a high temperature for the soil (this may be advantageous in cooler regions).

This may be mediated by moving your plant around throughout the year to prolong its aesthetics. Which brings us to the next point, the weight of the containers.

How Container Weight Affects Growing Citrus

Plastic pots and are lightweight; hence they are much easier to move your citrus trees around to protect them from harsh environmental conditions. Pot weight is also important for potted trees that are top heavy, for instance when your citrus trees start producing fruit. If the pot weight is too low, your citrus trees may topple over with high wind speeds or by just brushing against them while gardening.

Heavier pots such as terracotta or clay pots may be an alternative, but it may be a harder task to move plants around and more frequent watering may be required. These pots have great aesthetic appeal because of their elaborate designs and vibrant colors.

Newer fabric/cloth pots have been developed. These are inexpensive and light. Our favorites have handles and can be found in different colors. Though these do not have drainage holes, the mesh allows proper drainage from the bottom and the sides (every spot that the fabric touches the wet soil).

Container Color

Container color also plays an important role in the plant health. Darker pots absorb more heat than light-colored pots, hence soil temperatures may increase dramatically during the summer months. This increase in temperature may lead to the drying out of the soil and will require more frequent watering to keep your citrus trees healthy. On the other hand, darker colored pots may help your citrus trees during the winter months when temperatures drop below the optimum growing threshold.

Container Shape

The shape of the container is important in that the mouth of the pot should not be narrower than the body. There are multiple containers sold which are of this style, and they are attractive, however, it will become impossible to remove the tree once it has established roots without breaking the pot.

Citrus Tree Pot Drainage

The drainage of the pot is also critical for optimal citrus tree growth. Adequate drainage is required in the pot because water accumulation can lead to root rot on your growing trees. Some showcase pots may not have drainage holes on them. This can be ameliorated by double potting your plants, but unless your citrus tree is small enough this may not be an option. Additionally, the addition of a bit of gravel or rock at the bottom of pots to improve drainage is common practice, but this should not be done. Water will only drain into the rock below when no air space is left in the soil, so this practice will not prevent soil saturation due to overwatering.

Container Size

Container size should be adequate for the type of growth your plants or trees will go through. Root growth restriction has been known to result in low plant growth. The physical stress placed on the roots may also lead to root surface damage which may be an entry point for microbes that cause various plant diseases and even death. In citrus, container size has a profound effect on tree growth and fruit production by restricting root growth.

A study evaluating the growth of Mandarins under root restriction conditions found that the height, canopy volume, girth, and leaf area were all affected by root restriction, while some physiological activities like photosynthesis and transpiration were not affected.

Surprisingly, root restriction improved the number of fruit per volume of the tree canopy, total soluble solids, and fruit color. There are some citrus species that will grow vigorously and will need to be transplanted more often than others.

What We Recommend:

We recommend a 15-gallon pot, as it is large enough for young citrus trees, but it is not too heavy to move, especially with a single person (take all normal precautions for moving heavy objects). We believe 25 gallons is the upper limit of size for young trees because of the resulting weight when the trees need to be moved with inclement weather.

Also, consider size when bringing pots indoors. A 15-gallon pot would be able to accommodate a 24” garden saucer (available on Amazon or local garden centers) which would be placed underneath your pot if you bring your tree indoors. At a minimum, we recommend at least a 5-gallon size pot for young micro-budded trees.

Repotting Your Citrus Tree:

Traditional recommendations have owners repotting your tree as it grows, every year or so. This does not hold for young micro-budded citrus trees. The micro-budding process causes the trees to grow very rapidly, with significant root development, so there is no need to change sizes and “build up” to a 15-gallon pot, just plant once.

Using a hard container (all except fabric pots), there will be a bunching of the roots every 4-5 years or so. At this point, your citrus tree health, growth, and even water drainage may be compromised. We recommend repotting your citrus tree at this time and trimming the “root ball” which will have developed. The aeration of fabric pots minimizes this phenomenon. However, a citrus tree will likely need transplanting every 4-5 years for cosmetic reasons of the pot, or the above-listed reasons.

As you can see, when selecting a container to grow your citrus trees is not as simple as just liking how it looks. A great deal of planning and foresight is required to ensure your citrus tree investment will yield deliciously beautiful fruit for years to come.

References

1 Andrew “Drew” Jeffers, Spartanburg Cooperative Extension, Horticulture and Natural Resource Agent, Clemson University, 11/17

2 Mays, D., K. Richter, L.K. Bradley, J. Sherk, M. Kistler, and J. Neal. 2017. Plants Grown in Containers, Chpt 18, In: Moore, K.A. and L.K. Bradley (eds), North Carolina Extension Gardener Handbook. NC State Extension, Raleigh, NC http://content.ces.ncsu.edu/18-plants-grown-in-containers

3 Mataa, Mebelo, and Shigeto Tominaga. "Effects of root restriction on tree development in Ponkan mandarin (Citrus reticulata Blanco)." Journal of the American Society for Horticultural Science 123.4 (1998): 651-655.

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