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About 8.5 years ago I successfully germinated a lemon seed from a store-bought lemon (I believe it was a Eureka lemon). Fast-forward to today and that lemon seed has grown into a 9-foot tall tree. Luscious green leaves, a 2-inch diameter trunk, and several branches, it would probably be over 10-foot tall if I never pruned it.

Things to keep in mind:

To this day I have not seen this tree produce a single bloom.

This tree lives in Pittsburgh, PA, and spends its time indoors from October through mid-April.

It receives as much sun as possible when outside. While indoors, I have it seated on a heating mat with white LED grow lights 10-12 hours a day and the indoor ambient temperature ranges between 62F - 72F.

I have never left this tree outside during a frost. Obviously, citrus trees do not grow this far north so I had no viable scions around me. Therefore my lemon tree is not grafted.

2 - 3 times per year this tree will go through a rigorous growing phase, putting out new shoots on the upper branches. I usually have to cut some of these back to allow the tree to fit in the house. I have been told the highest branches (i.e. the newest branches) will be the first to produce blooms. Hopefully, I am not cutting the branches that would produce a bloom.

The leaves emit a strong lemon scent when torn or ripped.

The tree is fertilized every 3 months with 1 Tbsp of CITRUSGAIN (https://www.bgi-usa.com/citrusgain/). The tree is watered with distilled water and/or rainwater 2x/week, I allow the soil surface to dry between waterings. But for the past 10 months, I have watered this tree with a mixture of 5 tsp Tiger Bloom (https://foxfarm.com/product/tiger-bloom-liquid-plant-food) per 1 gallon of distilled water. I have heard the high phosphorus content could help promote the growth of blooms.

Is it possible that this tree will eventually produce blooms? I understand that without grafting, I am not going to see the same fruit that the seed came from, but instead some lemon/citrus derivative, that's if it ever produces. I have heard that a non-grafted tree like this may take up to 15 years before it produces any blooms or it may never produce a bloom...ever! Some farmers have told me to expect blooms during the 5th year. As I mentioned above, I have to cut the newest branches to allow the tree to fit in the house. Is it possible to graft those cut branches to a lower section of the tree and allow the branch to grow out and possibly produce a bloom?

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  • LED growing also in winter? Do you fertilize also in winter? The plant may lack the winter. Dec 26, 2019 at 16:56
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    @GiacomoCatenazzi yes I have a LED light on 10-12 hours per day. I do fertilize in the winter with the citrus gain that I mentioned. Do you think the tree is missing out on the “chill hours”? Due to the size, the tree is quite cumbersome to move in and out of the house frequently. It is staying inside until at least April.
    – giuseppe
    Jan 16, 2020 at 4:08
  • Excellent question; Sounds like your Lemon Tree is very robust! And a seed should likely be able to produce more seeds! Flowering is usually on the justprevious season/activity growth, & instead of grafting, maybe propagate by rooting! .. good comment; thank you!
    – M H
    Jul 29, 2020 at 9:17
  • @M H I agree, I fully believe it should be able to produce more seeds. But flowers need to come first. I might try to put this tree in an insulated grow house during the cold northern months in hopes of better simulating the warm climate its genes are accustomed to. 3 months ago I grafted many varieties of citrus (mandarins, oranges, limes) onto this tree. Some of the grafts healed and some didn't make it. The apical domination phenomenon will probably prevent most of the grafts from growing out and I don't really want to cut the tree in half to break that phenomenon.
    – giuseppe
    Jul 30, 2020 at 13:46
  • Same here with an indoor 13-years-old lemon tree!! Not even a single bloom :'-(
    – Noil
    May 30, 2022 at 15:21

1 Answer 1

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If the lemon tree has tolerated the cold, but is being kept above 15℃ (60℉) during the winter months, it will not accrue enough chilling units/hours.

To maximise flowering potential, you will need a minimum of 100 chilling hours, +5℃ above the minimum tolerated temperature for your lemon tree, which could be as low as 10℃ (50℉).

You already seem to be providing enough: light, nutrients and heat.

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