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NOTE: This post contains excerpts from my book, The Complete Mini-Guide to Growing Windowsill Lemon Trees: A Reference Manual for Northern-Zone Gardeners. The book is a comprehensive instruction manual for growing potted lemon trees indoors, and may be purchased on Amazon in ebook or paperback formats for less than the price of a fancy cup of coffee!

Caveat: This is not a “How to Grow Lemon Trees in Containers” post. This is a “all the things I’ve done wrong that you shouldn’t do” post. (I don’t call this an epic-fail blog for nothing.) If you’re looking for an awesome “how-to” post from a reputable nursery, scroll to the bottom and there’s a link to other internet resources.

I LOVE citrus. The smell, the taste, just the vibe. That addiction has turned into a major passion for citrus gardening, specifically growing lemon trees… a tough hobby in a zone where winters regularly drop 20 below zero. That being said, I’ve grown – and harvested! – from lemon trees right on my windowsill, right alongside other the other potted citrus trees on my windowsill including lime, tangerine, and orange trees.

In these years of growing potted fruit trees, I’ve learned a lot about what NOT to do when growing citrus trees in zone 4. In the interest of furthering every fruit garden’s goals of world domination, I share those embarrassing moments with you!

CHOOSE ONLY DWARF CITRUS TREES FOR CONTAINER-GROWING

Yes, I’ve grown citrus from random supermarket-lemon seeds. Did they ever produce? No way.

Am I sorry I tried it? Not really. I never really trusted all the other folks who said it wouldn’t work, and trying it out for myself cost nothing other than time because I had “backup” in the form of nursery stock. Dirt is cheap, and so are the seeds I found in my supermarket oranges, halos, and other citrus fruits. It was kind of fun. Epic fail, but still fun.

That being said, if you want actual fruit, the object of the game is to grow a DWARF tree from a reputable nursery. Because it takes several years to develop a seedling into a fruit-bearing tree, you don’t want to take a chance on dud from a cheapo internet sales company.

Looking for a nursery that sells dwarf citrus trees? I have always been happy with every citrus tree I’ve purchased from Stark Bro’s as well as Logee’s, and I although I’ve never bought citrus from Jung Seed I’m always satisfied with everything else I’ve ever purchased from them.

I know there are many other sources out there as well, but these are three nurseries I personally have tested and am happy with.

Container-grown lemon trees have become a popular hobby in recent years, and local nurseries as well as farm & garden stores have started carrying potted or “sleeved” trees in their gardening sections. If you are purchasing a plant with no information to go on other than a plastic plant marker or the label slapped on the pot, consider taking a snapshot of the pot with your phone and going home to look up more information on the cultivar first. 

If you aren’t sure what tree is right for you, read more on choosing a dwarf lemon tree.

MAKE HEAT & LIGHT ADJUSTMENTS GRADUALLY FOR POTTED TREES

Citrus trees are technically not terribly delicate. HOWEVER, when you drag them out of their natural balmy environment and drop them into a frigid foreign zone, the tree is under a massive amount of stress. Keep in mind that you’ve already messed with the tree’s system just by owning it in a cold zone. Don’t add any more stress to your windowsill citrus trees if you can help it!

The biggest stumbling block I have stumbled on is the light regulation. Beware of movement. Drastic changes from light to dark are rough on a plant that still believes it is rooted in the ground, not a movable pot. All the plant’s internal brain can associate light/dark with is seasonal changes, and it recycles to a new set of leaves to accommodate those changes.

Case in point: Knowing a cold snap was coming, I removed my potted lemon to a warmer spot and never even considered that it was a significantly darker location. OUCH. The leaves yellowed and dropped like flies.

Less than a year later I made the same mistake, and lost LITERALLY EVERY SINGLE LEAF ON THE TREE. Everything. The plant survived the herculean effort of replacing all those leaves, but I was biting my fingernails in panic

Solution? Try to make lighting changes gradually. You’ll still lose leaves, but it’s easier on the tree when it doesn’t have to make the change all at once.

Also, keep in mind that there’s more light in the warmer zones, even in winter. The tree will still go semi-dormant for the cold months, but even in that sleepy stage it needs more light than it typically would get in a northern winter.

Consider supplemental lighting on your windowsill – not enough to freak out the tree and make it start producing summer leaves, but enough to keep it content.

ADDRESS PRUNING, SOIL FERTILIZER & WATER

Be thoughtful about when and how much fruit you allow a potted lemon tree to set. The first few years (length depends on the cultivar and age of the seedling when you purchase it) should probably be left alone to let the tree pump resources into a strong trunk and limb system. I know it hurts, but try to pinch off the blossoms.

When I bought my first lemon tree it had already set a baby lemon, even though the tree was absolutely tiny. Thinking that this experimental tree probably wouldn’t survive container-growing on my cold windowsill, I let it stay…

… and the tree survived and I harvested my lemon, but the tree has always been a little misshapen from that early weight. I could have had a much bigger, nicer tree much faster if I’d been a little more ruthless. My own stupid fault.

Bottom line? Learn when to thin fruit, when to prune, and when to pinch off blossoms. Your tree needs the appropriate structure to support the weight of a heavy fruit load, or it will damage and destroy fruit-bearing limbs while stunting growth possibilities.

Pruning isn’t hard; it just needs a little attention from the gardener. (Bonus points? You can turn the branches you prune into cuttings. Not all will root, but it’s a completely free experiment that may net you more trees.

Soil also matters. Get yourself some good citrus fertilizer and learn how to use it. Please, please, please don’t shock the tree – same rules that apply to lighting apply to fertilizer. Your tree is already under stress, and you want to gradually introduce anything new.

Yellowish leaves with dark green veins are a good sign that the soil needs some work. I’m no expert – my one attempt at adding Epsom salts was brutal on the tree because I overdid it and nearly killed the thing – but there are lots of resources that can help you figure out what exactly to add and when.

Lastly but CERTAINLY not least, you need to be super careful about watering this tree, especially in winter. Believe it or not, less is more. When the plant starts to slide into dormancy, water causes problems because:

a) frigid water can mess with soil temperature and rot out the roots for a heat-loving plant, and

b) overly warm water can confuse the heck out of the plant (cold air + warm roots = very bad) or wake it out of dormancy entirely, which messes with internal systems and leaves the plant trying to put out new growth and run full-steam ahead during a cold, light-deprived winter season.

I live in a house with well water, and in January, our cold water is COLD. I tend to fill up a pitcher and let it sit overnight to reach room temperature before I water my potted subtropical trees. That way, I can be sure the environment of the roots is not upended.

I have a hard enough time trying to get my plants to survive zone 4 while dormant — I can’t imagine how it could get through the winter if it wasn’t snoozing. Read more about establishing the right temperature and humidity for growing indoor lemon trees in other excerpts from the book.

BEWARE: WINDOWSILL GARDENS INVITE BUGS!

Growing lemon trees on a windowsill means two things: Presence of all the wrong bugs, and absence of all the right ones. (Murphy’s law. Sorry).

Presence of all the wrong bugs? Well, be prepared for a massive invasion of spider mites. Growing indoors means your citrus trees are sheltered from the rain and typically the humidity is lower. 

What’s that mean? Spider mites love a low-humidity, indoor growing environment. These villains absolutely devastated my citrus trees until I realized what was going on. Solution? I spritz the trees’ foliage with a spray-bottle of water regularly. Doesn’t entirely do the job, but it helps control the population.

For a massive invasion of spider mites, I take a wet paper towel and sponge off the webby nests, which again is only a stop-gap measure but helps keep the tree alive until it can go outdoors into the life-saving summer heat & humidity & rainstorms. Note to self: Don’t use soap, be gentle, and only tackle the worst areas.

Absence of all the right bugs? Lemons tend to blossom and set fruit whenever they please. Chances are, the blossoms won’t all open in the height of summer when you have the plant outdoors for pollination. If you want the tree to set fruit (and because it can take a year to ripen, you almost always will want those blossoms to set), you are probably going to have to play worker bee yourself.

Solution: When the tree blossoms in the winter, get out a cue-tip and dust the pollen from one flower to another. It’s a massive pain, but it works.

GROWING WINDOWSILL LEMON TREES

Let me be honest. As with most of my fruit gardening efforts, most of what I’ve learned about growing lemons in pots over the years can be boiled down to a three-word motto: Don’t Be Stupid. Common sense gardening is key.

That being said, there are outstanding learning resources out there (I absolutely LOVE the Four Winds Growers’ Guide to growing dwarf citrus in containers. You can also get a more in-depth background from Alan Buckingham’s Grow Fruit, which is not container-specific but will still get you started).

I’ve still got a lot to learn about growing citrus trees indoors — especially since we’re talking about growing lemon trees in zone 4 — but I’m pretty confident that if I’ve survived through this many mistakes I can’t be too far from success.

(What is success? I’ll let you know if I ever find out. Right now, I’d be pretty happy with harvesting a full bowl of lemons from an indoor tree rather than a straggler here and there). In the meantime, bon voyage with your windowsill lemon gardening ventures!

Interested in learning more about growing potted lemon trees indoors? Check out my book The Complete Mini-Guide to Growing Windowsill Lemon Trees: A Reference Manual for Northern-Zone Gardeners (available on Amazon along with its companion book The Complete Mini-Guide to Growing Windowsill Pomegranate Trees!) or read more excerpts here:

This post was originally published in 2021. The post has since been updated to keep information and links current.

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