The climate in Arkansas ranges from U.S. Department of Agriculture plant hardiness zones 6b through 8b, while citrus trees (Citrus spp.) thrive in USDA zones 9 through 11. Because the average extreme winter temperatures in zone 8b, the warmest zone in Arkansas, dip to 20 degrees Fahrenheit and citrus trees only tolerate temperatures down to 28 degrees Fahrenheit, growing citrus outdoors is problematic. Arkansas residents can still grow dwarf citrus trees in planters that can be wheeled into a sun room, greenhouse or other indoor location in winter.
Citrus in Containers
Dwarf citrus trees are easily grown in planters or large flowerpots. Because the tree, pot and soil are heavy, use a planter or plant stand on casters so you can move the tree indoors when cold weather arrives. Begin with an 8- to 10-inch container for a 1-year-old tree. A 2- to 3-year-old tree can be moved to a 12- to 14-inch-diameter pot. As the tree grows, keep moving it to the next size larger pot, up to 20 inches in diameter.
Citrus trees prefer a slightly acidic, organically rich, well-drained soil mix. Use an acidic potting mix, 2 parts outdoor potting mix combined with 1 part wood shavings, or prepare your own by mixing equal parts sand, wood shavings or peat moss and well-decomposed compost. Place a piece of window screen over the drain holes to keep the soil in when the water drains from the pot. Plant the tree in the moist soil at the same level as it was in the growers pot.
Water and Fertilizer
Water the tree every five to seven days with 1/4 to 1/2 gallon of water, adding water until it drains from the bottom of the pot. Monitor the tree to ensure that the soil is moist, but not waterlogged and adjust watering as needed.
Apply fertilizer in February or March, and then once every six weeks afterward. Use a fertilizer formulated for citrus, such as a slow-release 10-6-4 fertilizer. Scratch the fertilizer lightly into the soil, at a rate of 2 tablespoons the first year. After the first year, add 4 tablespoons for a tree up to 4 feet tall, and 1/2 cup thereafter. Always water thoroughly after fertilizing.
Prune the Tree
Generally, citrus do not require pruning except to shape the tree, remove broken or damaged branches and remove suckers. Trim overlong branches or rapidly growing water sprouts back as needed. Remove suckers growing below the graft or from the roots immediately; otherwise, the vigorous rootstock can overtake the desirable graft, and you'll have a thorny bush with less desirable fruit.
Move the tree indoors when temperatures begin to drop. Citrus trees prefer temperatures between 55 and 85 degrees Fahrenheit. While the sheltered sunny corner in the garden is a good summer home, move the tree indoors when temperatures drop to 55 degrees. Put the tree in front of a window that receives four to eight hours of sunlight daily, or supplement with a grow light. A cool steam vaporizer adds moisture to the air around the tree.
Dwarf Citrus Varieties
While growers are developing new dwarf citrus, on their own rootstock or grafted onto the 'Flying Dragon' (Poncirus trifoliata, USDA zones 5 through 9) dwarfing rootstock, there are already a number of tried and true varieties for the citrus enthusiast.
- 'Clementine' Mandarin Orange (Citrus reticulata 'Clementine', USDA zones 9 through 10)
- 'Dwarf Redblush' Grapefruit (Citrus paradisi 'Dwarf Redblush', USDA zones 9 through 11)
- 'Dwarf Washington Navel' Orange (Citrus sinensis 'Dwarf Washington Navel', USDA zones 9 through 10)
- 'Improved Meyer' Lemon (Citrus limon 'Meyer Improved', USDA zones 9 through 10)
- 'Mexican Thornless' Lime (Citrus aurantifolia 'Mexican Thornless', USDA zones 10 through 11)
While true citrus are cold-tender, citrus relatives kumquat (Fortunella spp.) and hardy orange (Poncirus trifoliata) are more cold-tolerant. These small trees and shrubs have the same soil, water and fertilizer requirements as other citrus trees.
Kumquat is hardy down to USDA zone 8a and thrives in the summer heat of USDA zone 10. Kumquats are often grafted onto the rootstock of hardy orange, also known as 'Flying Dragon.' Kumquats need winter protection from severe freezes that dip below 10 to 15 degrees Fahrenheit. 'Nagami' (Fortunella margarita Swing.) produces small, citrus-like fruits, 1 3/4 inches long and 1 3/16 inches wide. Kumquats may be eaten raw or made into marmalade, sweet pickles or sauces.
Hardy Orange Shrub
Hardy orange is a thorny, deciduous shrub that may be grown in all Arkansas USDA zones. The 1- to 2 1/2-inch lemony fruits are edible, but acidic, and may be made into marmalade. A row of shrubs can serve as a protective border around the garden; the thorns are vicious.
- Lowe's: Dwarf Fruit Trees
- Four Winds Growers: Growing Citrus in Containers
- Monrovia: Clementine Mandarin Orange
- Monrovia: Dwarf Redblush Grapefruit
- Monrovia: Improved Meyer Lemon
- Monrovia: Mexican Thornless Lime
- Missouri Botanical Garden: Poncirus Trifoliata
- Floridata: Fortunella Spp.
- Fruits of Warm Climates; Julia F. Morton