Hi!
I'm admittedly horrible at growing things, but when my aunt passed away they passed out lemons (Meyer?) at her memorial and I planted its seeds in her memory. One seed grew but based on everything I've read, it's growing half as fast as normal. It's 3 months old and barely 3" tall with a couple of leaves. I recently put it in a bigger pot with fertilizer which helped, but what else is wrong? And now it has a weird-shaped vertical leaf at the top! Please help! I don't need fruit, but want a luscious lemon tree!

That pot is HUGE! It will grow into it in a couple years. Repotting AND fertilizing... Potting soil comes with a built in 6 month supply of fertilizer and you added more fertilizer. Trees just don't need that much, especially twice the recommended dose. Next time you fertilizer (next spring), use citrus specific plant food at half strength - repeat in early summer and mid-summer. That leaf is the result of dealing with all that plant food.

Citrus produce two types of seed. If the seed is polyembryotic (more than one embryo per seed), the tree will be a meyer lemon. If the seed is Monoembryonic (one embryo), the tree will not be a meyer lemon. Because that seed grew just one tree, it may be monoembryonic as polyembryonic seeds produce multiple trees. That may also account for why this tree looks different then the others.

Forgot to add: Monoembryonic citrus seedlings are less hardy than polyembryonic seedlings.

I would say the condition of the plant is not your fault. Lemons are poly---germa? something. I forget the Latin term, but it means there is more than one plant waiting to sprout inside the seed coating. If all you got was one seedling emerging from the seed, the lemon had poor pollination. It is almost impossible to over come poor pollination issues. It's kind of like a birth defeat. The tree will have to work three times harder to grow half as much.

Lemons like full sun and good drainage. Give it a little osmocote. Not too much, it is pretty little and it is likely to stay little.

Daisy snuck in while I was writing. Obviously she knows better because she actually knew the Latin term!

I was under the impression all varieties of lemons are polyembryonic, and that monoembryonic only occurred when pollination was incomplete. I'll have to go research that now.

Hello and welcome!
I have grown citrus from seed. (Mine were polyembryotic, heritage type mandarins from Japan. They are now 10 years old and pruned to 3 feet tall.) Three inches in three months is fine. Occasional weird leaves are kind of par for the course. I would recommend following Daisy's advice on fertilizer, it is much easier to over-fertilize than under and you are growing this plant as a memorial, not a summer crop.

Best of luck.

It is sunlight and proper watering that lead to maximum growth. Fertilizer and larger pots do not stimulate growth as a general rule. In fact, over potting a plant can retard growth and excessive fertilizer can burn tender roots on young plants.

Please tell me what kind of seedling is this... I threw some citrus seeds not knowing it's variety.