Answer: Meyer Lemon trees need a well draining soil - any commercial brand of potting soil will work. You don't need to add anything to it or use the expanding co-polymers to help with moisture retention. You can use Miracid or Miracle-Gro liquid as a fertilizer. I prefer using a liquid product and diluting it by half-strength then using it every 2-3 weeks on my potted Meyer Lemon. This way, the tree gets a constant source of nutrients and I don't have to worry about over-fertilizing and burning the roots or leaves.
As for which container to use - pot size does matter, but either plastic or terra cotta will be fine. Plastic holds moisture better - terra cotta wicks moisture away from the soil and as it evaporates, it increases humidity near the plant. Terra cotta pots will need to be watered more frequently. As for pot size, it's best to use one just slightly larger than the old one; as the tree grows, you'll need to bump it up to the next larger size.
Hope this answers all your questions and helps you help your Meyer Lemon tree grow happy and healthy.
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