For most windowsill gardeners, half the fun of growing unusual fruits is the challenge associated with keeping a warm-climate plant healthy and thriving in a climate where it would otherwise never survive. The other half of the fun? Harvesting and showing off the fruit!
For windowsill gardeners growing potted lemon trees, achieving a healthy fruit yield typically requires some involvement in the pollination process. The majority of lemon trees are self-pollinating, which means that you don’t need multiple trees for bees and blossoms to do their thing. Even if your tree is a loner for its entire life, you have the right to expect fruit… you just may need to intervene a little. Fortunately, helping your lemon tree (or other windowsill citrus tree!) successfully pollinate its blossoms is a fairly simple and straightforward process.
**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!**
WINDOWSILL LEMON TREES: IS CROSS-POLLINATION NECESSARY?
Although the lemon tree is technically self-pollinating, there’s room for debate on whether adding a second tree will increase your fruit yield. Theoretically, a second tree of a different variety should add a vitality boost to your tree; this is how it works in their natural environment and in orchards across the world. However, on a windowsill it’s not quite so simple.
Dwarf trees are very small. A dwarf tree confined to a pot is even smaller. (Make sure you’ve selected the correct pot size for a container-grown lemon tree.) These tiny trees only produce a tiny number of blossoms at any given time. If you have two or three trees for cross-pollination, that’s great – but they may not all bud out at the same month, and if they do, the blossoms may not open within compatible timeframes. Personally, I have multiple lemon trees, but I was always satisfied with the fruit set for the first five or so years that my tree was a loner.
Another concern to keep in mind is that “self-pollinating” doesn’t necessarily mean that you won’t need to help the tree out a little when the bees aren’t around. A windowsill tree – by definition – is often segregated from the bees and other insects that do most of the world’s heavy lifting when it comes to pollination. For the summer season when your tree can be set out onto a patio, this isn’t a problem; the local bees will take care of all the blossoms that open up as long as the tree is outdoors.
However, lemons don’t just blossom in the summer. Instead of focusing all their blossoming efforts within specific seasons like fruit trees from more temperate zones do, lemons tend to blossom and set fruit whenever they please. Chances are, the blossoms will open all throughout the year, not just in the 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 will almost always want those blossoms to set), you are probably going to have to play worker bee yourself upon occasion.
POLLINATING WINDOWSILL LEMON TREES: FLOWER ANATOMY
If you aren’t familiar with the anatomy of a flower (who can really remember all those diagrams from grade school?), you can still pollinate your lemon tree! Most of the pollen will be hanging out on the anthers – very flexible, wavy stalks in a ring around the center of the flower. Your goal is to transfer pollen from the anthers to the stigma – the top of the big center stalk within the flower. This stalk is significantly larger than the anthers.
If the pollen sticks to the stigma, you’re in good shape. If it does not, the flower may not have been mature enough; you may need to wait and try again. If possible, transfer pollen across multiple flowers (and multiple trees if you have the option). This should increase your success rates and fruit yield.
To successfully pollinate when the tree blossoms in the winter, use a small paintbrush (dry, obviously) or a q-tip and dust the pollen from one flower to another. It’s a delicate job that takes close attention, but it works. If you are really in a rush (and you don’t have to worry about creating an Instagram-worthy photo of the process for your green-thumb blog), you can cheat by gently plucking off one flower and rubbing its face into the other open blossoms on the plant. It’s not exactly a recommended practice, but I’ve done it and it works like a charm.
HOW POLLINATION AFFECTS WINDOWSILL LEMON TREES
Even if you don’t intervene in the pollination of your windowsill citrus tree’s blossoms, you will probably still see some fruit production at the end of the growing season. This citrus tree tends to blossom year-round, so if you have it outdoors on a patio in the summer months, the local bees will do as much as they can to boost your fruit yield without any involvement from you. However, for the winter months, you are on your own; you can choose to skip providing any assistance in pollinating the tree, but you just need to be aware that if there are no pollinators present (whether natural or artificial pollinators), the number of fruits successfully set may decrease – and the size of the fruit may be smaller also. It’s up to you whether you think the fuss is worth the extra reward of more fruit at the conclusion of the current fruiting cycle.
Helping to pollinate your container-grown lemon tree may seem complicated at first, but it’s a skill well worth learning and you’ll find it comes in handy when growing other subtropical fruit on your windowsill as well. Give it a try!
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: