Last December’s hard freeze set back homeowners reestablishing citrus trees. A few residents that I have talked with swear they will never grow citrus again. My advice is to not give in to the vagaries of old man winter, to continue planting in-ground and consider cultivating citrus in containers. There are a number of advantages with container grown citrus: flexibility relocating plants before freeze events; great for homes with limited outdoor space; and cold sensitive varietals cultivated outside of their natural range.
Basics of Growing Citrus: Container Size
You will provide basic growing requirements with 6 to 8 hours full sun exposure to maximize performance, applying consistent water and scheduled fertilizer application. We must also consider container type and size in relation to varietal growth habit. The type of container is dependent on your practical and functional situation; molded plastic is lighter for ease of movement, terracotta and ceramic are heavier and larger containers may crack when moved. Eventually the container size must be potted up to 20-gallons minimum, a size appropriate to establish a healthy root system that will support top growth and fruit production. Upsizing should be performed incrementally at 25% more pot size; too much soil volume to root ratio disrupts equal distribution of water throughout the container. An example would be repotting from a ten-gallon to a twelve-gallon container. Assess the root zone annually to determine if repotting is necessary, and expect repotting every 3 years. Replant with similar techniques used for planting in ground: wash off the old media, prune malformed roots, plant at the same depth, etc.
Consider growth habit as each type of citrus has its own form, growth rate and eventual size. The largest trees are Navel oranges, grapefruit and pomelo, and can reach 15-feet or more in-ground; lemons at close to 15-feet; mandarin, satsuma oranges and lime trees to 12-feet. Citrus can be kept smaller stature by grafting onto specific types of rootstock. Unless otherwise stated on a product label, commercial citrus varieties are grafted onto a stump (rootstock) of a compatible sour orange. Trifoliate orange (Poncirus trifoliata) is generally used, is a cold tolerant sour orange species and has the potential to dwarf top growth to 10-feet. Varietal ‘Flying Dragon’ (P. trifoliata var. monstrosa) offers the same environmental tolerance and is known to keep species 6 to 8-feet. In conclusion of this topic, research the grafted rootstock of your desired citrus tree prior to purchase. You may have to root prune once you have reached your preferred optimum container size to maintain a balanced growth.
Fertilizer Scheduling
Commercial soil-less media blended for citrus provides good drainage, is lighter in weight and has adequate organic matter. Nutrient availability is managed through scheduled fertilizer applications. The primary nutrients listed on a fertilizer product are based on a percentage of nitrogen, phosphorous and potassium, represented numerically and in the order listed. Fertilizer ratio and application rates are calculated primarily for in-ground trees, and related to trunk size and identified nutrient deficiencies. For containers, it is best to use products with a 2-1-1 or 3-1-2 ratio. Fertilizer can be slow release prils or water-soluble granules, and commercial products will have recommended application information on the label. I have had success with a product developed and marketed for citrus, rated 10-2-8 as a water-soluble fertilizer, applied three times at 1 cup (.5-lbs) each application. Timing for the application is mid-February, early May and final mid-June. It is best to discontinue after late July to discourage tender growth at a time of winter dormancy. Fertilizer products are formulated from salts as mineralized elements. These salts will accumulate over time in the media; visible signs will be a thin sheen or crystallized crust on soil surface, as well as brown leaf tips, reduced growth and unusual wilting. You will have to flush accumulated salts from the soil with water every few years. Keep in mind that you will have to increase fertilizer amounts as the tree matures. Supplement with liquid fertilizers as needed and regarding identified nutrient deficiencies.
Pruning, Fruit Drop and Harvest
Pruning in late February or early March is performed for canopy shaping, height reduction, water sprout removal and adequate air flow through the canopy. Do not prune more than one-quarter of the canopy each year, and only as necessary. Heavy pruning can initiate extra vegetative growth that may reduce fruit production the following year. Citrus are known for prolific flower production starting in spring. You will experience up to 80-percent flower drop after this flush, as well as intermittent fruit drop during development and toward harvest. This is a normal occurrence and must be expected. Most citrus flower once in spring and take about 8 months to harvest. Limes and lemons are the exception, can have several flowering periods and have the capacity to produce up to three times annually. Depending on the size and maturity of the tree, consider thinning the fruit to conserve resources for sustained tree health and production. With a well-established tree, aim for one fruit for every 42 leaves.
Life is a bit brighter with citrus, we continue to celebrate citriculture through education efforts like Gulf Coast Gardening seminars and events. Keep on the sunny side and I’ll see you in the garden.
