In general, there is advice that says you should not overwater your citrus tree. This is important for all varieties of citrus trees, including lemons, limes, grapefruit, Calamondins, Kaffir lime, and Australian finger limes. This is because when you are talking about watering, you are primarily concerned about its effects on the root system.
Overwatering Citrus Trees
If citrus is overwatered, it can lead to a condition called root rot, caused by the Phytophthora pathogen, a fungal infection. In citrus groves, it is especially a problem where fields are flood irrigated. This is when, as the name implies, the entire field is floated using a system of pipes as irrigation. In these conditions, it is much easier to spread the fungal spores.
The roots can really be affected, especially when the roots are saturated in water. This is especially a problem when there is poor drainage of the soil. Well-draining soils ameliorate this problem, for example in the Rio Grande Valley, where US Citrus plants Eureka lemons, Meyer lemons, Persian limes, Kaffir limes, and Rio Red grapefruits, we do so in areas where there is good Sandy soil subtype. This Sandy loam soil is extremely well draining. Also, we used exclusively drip irrigation; this makes the control of potential fungal root rot of citrus trees much easier, minimizing risk.
The reason that issues for watering remains the same between different varieties of citrus is that citrus trees are all grown from a rootstock, think of a citrus tree as two different trees fused together. That is the grafting process that is done at US Citrus nurseries. So basically, the roots of all of the trees are the same, as we use either a sour orange or trifoliate rootstock, and the citrus variety differences are in the top parts of the tree.
Now getting to practical points for the backyard gardener, here at US Citrus we recommend that nearly all gardeners growing citrus in the United States grow their trees in pots. This is so that they can bring them indoors or in a garage during the wintertime. Only areas in the southernmost United States like the states of California, Florida, Texas, Louisiana, Arizona, Georgia can support citrus being grown in the ground. All other areas, citrus planted in the ground will die from freezing weather.
Because of this unique situation of growing citrus in pots, this throws the old adage of not overwatering your citrus upside down. It is extremely hard to over water citrus that is kept in a well-draining pot and is outdoors. Especially in the summertime and in hot area conditions, we have never seen had an issue with a customer who has overwatered their citrus tree. However, we have had multiple customers send us pictures of citrus trees doing poorly from underwatering.
This is because the citrus tree is in a pot, using standard potting soil, and if it has good drainage holes on the bottom, or it is a mesh type pot which allows good aeration and drainage throughout the fabric type pot, then you are effectively controlling the drainage and making it excellent.
The only time we have experienced customers having problems overwatering is when they are keeping the trees indoors. At this time, there is often a garden saucer placed underneath the tree, and if the garden saucer is full of water and there is constantly water being poured into the soil, this will become waterlogged and the citrus tree will wilt and die.
Underwatering Citrus Trees
Underwatering is especially tough on your tree when it is young, growing, and trying to establish a good root system. We recommend our baby trees to be watered 1-2 gallons at its base daily for one month, then follow our citrus tree care guide instructions we send you.
I myself have moved my 15 citrus trees in pots, and in the wintertime, I moved my trees into the garage. I did use a space heater for a period of time while I was away. I made the mistake of not having a garden saucer underneath every tree fully saturated with water, knowing that I would not be watering for about 10 days. When I got back from a vacation of 1 week, my citrus trees, even though it was wintertime and they were inside a watch with no lights, they all suffered from dehydration because of the dry heat from the space heater. So, it is important to watch your citrus tree for signs of underwatering year-round. This will manifest as leaf drop, browning and wilting of the leaves, the soil being somewhat dry to touch, and the lack of vigor overall of the tree.
One friend of mine adores his citrus trees. He had some construction being done in his backyard, so he moved his trees into the garage to protect them. However, this was summertime in West Texas, and garages can get 120 degrees or hotter! Unfortunately his well-cared for, thriving trees died in just 2 days in that extreme heat because he neglected to significantly increase the water needed for those trees. If the situation could not be avoided, I would have recommended a garden saucer with 5 lbs of ice placed around the saucer every day it was in the garage.
Like my father, Dr. Mani Skaria, says, “It is very important to look at your tree and assess for signs of overwatering and underwatering.” And from our experience, it is much easier to underwater your citrus tree than it is to overwater!
Contributor. "How Much Water a Citrus Tree Needs a Week?" Home Guides | SF Gate, http://homeguides.sfgate.com/much-water-citrus-tree-needs-week-57157.html. 15 March 2018.
Rouse, R. E., & Zekri, M. (2015, February 05). Citrus Culture in the Home Landscape. Retrieved from http://edis.ifas.ufl.edu/hs132