Mary H. Meyer, Extension Horticulturist
Photo 1: Calamondin orange trees need maximum light, such as the south facing window, shown here. Photo taken January 4, 2014
"Oh my! How do they expect me to grow an orange tree in Pennsylvania?" my Grandmother Rena Anderson exclaimed as she unwrapped her Plant-of-the-Month gift on a summer day in the 1960's as we sat in her screened porch amid her many plants. She laughed and potted the tiny plant. Today I enjoy this same orange tree in an even colder Minnesota climate and yes, it produces oranges!
The calamondin orange ( Citrofortunella mitis) is a tough houseplant IF you have enough sunlight and can keep it watered in well drained soil. My plant spends May-October in an unheated porch with large south facing windows and the rest of the year in a corner of my living room with south and west facing windows (Photo 1).
In other words: the brightest light we can supply in Minnesota. Over the nearly 50 years since my grandmother received it, I have moved it through 5 states, 12 homes and many repottings. In October 1986, the orange tree was the last thing I put on the moving van in Philadelphia and the first thing I took off when the van doors opened in Plymouth, Minnesota a few days later.
I am attached to the orange plant as it was my grandmother's, and she was one of my plant mentors. But this orange can fill my porch or living room with a sweet orange blossom fragrance and it sets fruit well enough, that most years, I can make marmalade.
Here is a brief history of some recent orange harvests:
Calamondin Oranges ------------- Harvest Date
112-------------------------------- January 9, 2011
52-------------------------------- November 25, 2012
25-------------------------------- September 21, 2013
27--------------------------------January 5, 2014
Here is what I have learned from, yes, only 1 orange plant, over the years:
Bright light for several hours every day is necessary for citrus to do well in Minnesota. Moving the plants outdoors in the summer really helps. Gradual exposure to direct sunlight in the summer is important, as leaves that develop indoors are not able to grow outdoors unless they are acclimated; they easily get sunburned.
Adequate water is also essential. Citrus leaves are thin and easily wilt. Regular watering is essential for good growth. Just as important is good drainage, water should never stand at the bottom of the container. For many years, I used a plastic container, so I did not have to water as often, however today the plant is in a clay pot and it prefers the better air exchange for the roots.
Citus requires a lot of nitrogen and iron to grow well, and iron is often unavailable in high pH soils, which tends to happen over time with the alkaline water we use on indoor plants. Yellow foliage is a common sign of iron deficiency in citrus and means you need to add a fertilizer that has available or water soluble iron. Throughout the summer, I use a readily available, water soluble fertilizer, such as 20-20-20 once or twice a month. In the winter, I rarely use fertilizer. And about once a year, I use an iron supplement to keep the foliage a healthy green color.
After a few years of treating mealy bugs, I gave up on insecticidal soaps, which will control most insects and used a stronger systemic control that eliminated the mealy bugs. However, I did not eat the citrus for two years. Careful, regular inspection is necessary to prevent insects from becoming a problem, especially if plants are exposed to other plants or outside conditions.
Meyer lemons are also fun to grow and will produce a few lemons in Minnesota. I bought two plants a few years ago and they have produced about 5 lemons in total. These lemons take a long time to ripen (months) and are a pale orange instead of yellow when ripe. These semi-sweet lemons are a cross between a lemon and an orange, so they are much milder than regular lemons.
The tree was brought to the United States from Beijing, China in 1908 by Frank Meyer, a plant explorer of the U.S. Department of Agriculture, (no relation to me :(). The plants can be gangly and leggy plants; you should prune them after harvesting the fruit, to keep the plants in a manageable size and shape. Growing conditions are similar to calamondin oranges, however be sure to purchase plants from a reputable garden center so you do get the true Meyer, or Improved Meyer lemon.
A fun fact about citrus plants is they can have evergreen foliage, flowers, immature and mature fruit all at the same time. For Minnesota, it is fun to have fragrant flowers, and developing attractive fruits over the months when we often see too little green.
I have two daughters, and I may have to propagate my orange from a softwood cutting in the spring so they each have a plant to enjoy in their homes.
But for now, I plan on harvesting Grandma Rena Anderson's calamondin oranges for many years to come.
Four Winds Growers in California is one supplier for indoor citrus plants: