14 Things Nobody Tells You About Indoor Citrus Trees

Citrus trees are trendy. The proliferation of portable trees—grafted onto dwarf rootstock—makes it possible for almost anyone to grow a lemon, lime, or kumquat without having a large space.

With the rise in popularity comes the challenge of citrus care, especially in climates with hard winters, when the subtropical trees must overwinter for months indoors in conditions that can be stressful to the plants (and sometimes to their owners). Indoor winter conditions are challenging, with lower humidity, higher and drier heat, and more difficult watering protocols.

While we feel that we have turned the winter corner and are headed toward spring, this final stretch is a crucial one for overwintered citrus, when problems that have been building up sneakily can threaten the trees we love.

Read on to learn what you might be doing wrong with your overwintered citrus, and how to fix it.

Photography by Marie Viljoen.

1. Poor drainage can kill citrus trees.

Above: The annual citrus migration in my house in Brooklyn (USDA zone 7b) begins when nighttime temperatures begin to dip reliably below 50 degrees Fahrenheit. In October my collection of two sturdy Thai limes (Citrus hystrix, also called makrut), a Meyer lemon, and a petite finger lime (Citrus australasica) is herded indoors for a long winter stay.

Citrus trees require outstanding drainage. Soggy bottoms will kill them Water must flow right through the pot and out. I mix my potting medium with large handfuls of shredded hardwood (I use a natural cedar mulch – meaning no nasty dyes). Softer woods like pine break down too fast. My mix is one-third shredded wood to two- thirds potting medium. My pots have large drainage holes in the bottom. If your pots are set in an ornamental, closed pot, it is imperative that you never allow them to stand in water. If the water stands for more than 12 hours after watering the tree, drain it (see No. 2). More work for you, but essential.

Signs of poor drainage: damp pot bottoms, constantly moist soil, fungus gnats in the room, yellow leaves, drooping leaves, leaf drop.

2. Overwatering can kill citrus trees.

Above: On average my citrus trees spend about seven months inside, going back out in late April. I have learned, sometimes the hard way, how to care for indoor citrus, so that by mid spring they are in excellent health and ready to make a break for the great outdoors.

Citrus hate having wet feet, and overwatering is the most common cause of their poor health. Do water deeply, but only water again when the pot is close to dry. Nancy Lingner, who provides customer support at LemonCitrusTree (her daughter, Crystal Kim, owns the business) recommends that you drench the pot and “drown the soil” allowing the water to run freely from the drainage holes.

To do this, Nancy likes to keep trees on a stand above a substantial plastic saucer that can accommodate one gallon of runoff. Because of space constraints I use shallow pot feet and smaller saucers. If water in the saucers touches the bottom of the pot, I let it remain in the saucer for up to 12 hours (thirsty trees will absorb this water again). But after 12 hours, I suck up excess water with a turkey baster (yes, really).

I also like to use terra cotta pots. If the outside is dark and damp at the base, this is a sign that the soil in the bottom of the pot is too wet (even if the top is dry), which is not good, so I hold off on watering. In terms of touch and feel, the top inch or two of soil will also transition from dark and moist to the touch to lighter and dry. Time to water.

Signs of overwatering: the soil stays moist every day; the bottom of a terra cotta pot looks dark, or green, and is damp to the touch; water stays standing in the saucer; the leaves are drooping, but not dry and crisp; the leaves gradually turn yellow all over and drop; little bugs like fruit flies hover everywhere – these are fungus gnats and are an indication that the pots are staying moist too long.

3. Citrus trees also hate to be too dry.

Above: Less common than overwatering, underwatering tends to happen when you go away for a few days, or simply forget. Citrus trees need deep watering, so a spritz on the surface will not help them.

Nancy reiterates that “a few cups here and a few cups there” are ineffective. Establish a schedule (I water once every seven to ten days, for example), water the citrus trees deeply till water runs from the drainage holes, and observe how fast or slowly the pots dry out.

Signs of under-watering: the soil pulls away from the sides of the pot; when you water, the water sits on top of the soil for a while before draining; water runs quickly through the pot and out; the leaves droop, and turn crisp; branches die.

4. A moisture meter can save a citrus tree’s life.

Above: A moisture meter is a very helpful tool – I water again when it reaches 2-3 (after the drenching it should read 10).

To help take some of the stressful guesswork out of watering citrus, buy a moisture meter. Insert it fully into the growing medium. In larger pots it is helpful to take two to three readings in different spots.

5. Citrus trees hate cold water.

Above: Tooth-chilling winter tap water is a shock for subtropical and tropical citrus trees.

Their water should be tepid or at roughly the temperature of the room they are in.  I mix a little hot water with cold tap water, in a large measuring jug.

Signs of freezing water: yellowing leaf veins can also indicate that temperatures are too cold for plants to absorb nutrients; leaf drop.

6. Citrus trees love nitrogen.

Above: Signs of underfeeding include yellow veins on the leaves (which can indicate a nitrogen deficiency); drooping leaves; falling leaves. Leaves should be a healthy green.

Despite being indoors, citrus trees stay hungry, and they love nitrogen. In milder climates where they overwinter outdoors they slow down and feed less, but not inside. Inside, it’s summer. Winter is when I see a lot of flowers appearing and the setting of new little fruit; the energy required depletes the plant, which requires nutrition. Well-draining soil also means food washes out quickly: Every time you water, food is being made available to your tree. I feed my trees monthly with Citrus Tone, following the dosage instructions on the bag. Water immediately after fertilizing. You can also foliar feed often with a solution of liquid seaweed or fish fertilizer (this depends on your olfactory sensitivities; the smell will take about eight hours to dissipate).

7. Fertilizer sticks are a bad idea for indoor citrus trees.

Above: Like overwatering, overfeeding is not a good thing.

Avoid using fertilizer sticks in citrus pot. They can burn the trees’ roots. Using organic fertilizers decreases the chances of damaging your plant. If you use synthetic fertilizer, never exceed the recommended dose.

Signs of overfeeding: burned edges to leaves; leaf drop; very slow growth.

8. Citrus trees need to be near your sunniest window.

Above: Most citrus trees require six to eight hours of sunlight a day. A dark northern winter window will be insufficient.

When we moved recently, I looked at every potential new apartment through the eyes of my citrus trees. Was there outdoor space, and would there be enough light for them indoors in winter?

After weeks of searching, I walked into a top-floor space with skylights and ample southern windows flooded with sunlight, and knew this was it (even if there were not enough closets). There is a little wiggle room: whereas a Meyer lemon is uncompromising in its need for a minimum of six hours of sunlight, understory trees including Thai limes and finger limes are a little less demanding, as they evolved in semi-shady conditions. But if you must keep citrus in a less-than-bright room, boost the trees with grow lights. If you have a darker situation, full spectrum lights are very helpful.

But Aaron Dillon, the fourth-generation citrus grower and owner of Four Winds Growers in California, says that in cases where a tree receives “at least some natural sunlight” during the day, “a simple T-2 fluorescent can provide enough supplemental light.” A relief when considering your gardening budget.

Signs of low light: poor growth; green leaves drop from the tree.

9. Too much light can make citrus trees sleep-deprived.

Above: Signs of too much light include lack of growth and leaf drop. The trees above are happy.

Yes, citrus trees can have too much light. Aaron says that the mistake some people in northern climates make is to give the tree 12 hours or more of supplemental light, “which causes the plant to go into a vegetative state.” Think of them as sleep-deprived. They are stressed.

Eight hours of light is more than sufficient. Aaron points out that the goal is “to mimic the natural season as much as possible” because the citrus trees have specific seasons of flowering and fruiting. “By exposing the tree to too much light it can interfere with its normal production cycle and limit its ability to produce fruit.” It helps if you keep the nights cool. In our house the thermostat is set to a chilly 60 degrees Fahrenheit overnight (it saves on heating bills, too).

10. Citrus trees need to moisturize as much as you do in winter.

Above: Place plant pots on trays of gravel, so water stays in the saucer but does not touch the pot, raising ambient humidity.

Indoor winter air is notoriously dry. We moisturize,  but what can our trees do? At the very least, mist the trees daily with a spray bottle. But if you want to cut down on the time spent misting, invest in a humidifier. Kevin Espiritu, the founder of the website Epic Gardening and author of the forthcoming Field Guide to Urban Gardening (Cool Springs Press, May 2019), recommends a Honeywell Cool Mist humidifier “for serious plant parents” to boost humidity levels significantly.

Signs of low humidity: brittle leaf edges; leaf drop.

11. Citrus trees hate a draft … or a radiator blast.

Above: Keep your citrus trees away from hot air vents and radiators.

Do not expose citrus trees to cold drafts, either. Opening the nearby door or window for them on a cold day stresses citrus trees (and all plants). Stressed plants are susceptible to diseases and pests.

Signs of air stress: browning leaf tips; leaf, blossom and fruit drop.

12. You should ask your citrus tree if it’s having a good day.

Above: It’s all about paying attention. If you do not check your citrus trees every day, even when they seem healthy, you will not observe the early signs of problems.

Make it a ritual (consider it citrus bathing, and therapeutic). Observe the overall form. Is the tree looking well shaped and perky, or droopy and off? Go closer and look at leaves, turning them over. Are they green and upright, or beginning to yellow? A few slightly yellow leaves can be normal as the tree moves chlorophyll from older leaves to new, but perhaps it is underfed, or overwatered. If you see tiny cobwebs on leaves you may have the beginning a spider mite infestation. Is there shiny, sticky honeydew on some leaves? You have a soft scale issue.

As Nancy Lingner wrote to me in an email: “Where can a pest go for food in the middle of a Montana snowstorm? If you were a pest it would be a dream come true observing a scrumptious citrus tree just sitting there indoors in a warm environment.” Winter is the time to be watchful.

Signs of neglect: diverse – honeydew, sooty mould, cobwebs, dropping leaves, yellow leaves.

13. Don’t expect citrus tree problems to disappear on their own.

Above: Identify your problem or pest and take immediate action.

Problems will not resolve themselves. A chronically overwatered tree will die. A little honeydew and a few cobwebs will turn into an infestation.  You will find scale insects on the undersides or topsides of the leaves’ midribs: squash them with your nails. You can also wash them off the leaves with liquid dish soap, using a sponge and a tooth brush for tricky crevasses. Spritz the tree soap-free with a spray bottle of tepid water or rinse off in the shower if you can lift the pots. If the issue is serious, spray with Neem oil and repeat every three days until the invaders have left.

Signs of ignoring your trees:  general malaise, depending on the source of the issue.

14. Panicking at Leaf Loss

Above: Aaron Dolin says that it is common for trees to lose some leaves (even all their leaves) when they first transition from outdoors to inside.

“When it starts to happen,” Aaron writes, “people usually panic and start over-watering their tree (the biggest no-no with citrus)” or they move it to another spot. The solution is to pick a sunny window (preferably south-facing away from a heating grate) and stick with it for the whole winter season. “If the tree loses some leaves (even all its leaves) don’t panic. As long as they don’t over water the tree, it will usually recover.”

Does this all sound like a lot of work? It is. But tending your little citrus trees has tangible results and genuinely therapeutic value in an age when much of our attention is focused on screens.

The reward is exquisite and engages all our senses: being able to smell citrus blossom in your home in winter, and to pick and eat fragrant leaves and ripe fruit from your very own tree.

See more growing tips in Lemon Trees: A Field Guide to Planting, Care & Design in our curated guides to Edible Plants 101. Read more:

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