What and where ?

Here are photos of my mini meyer lemon and mini key lime. They came with three leaves at the base which I just removed. They have grown at least three inches in the past month, and seem quite sturdy.

As you see, however they are growing straight up. With any other baby plant I would have cut the top so it would branch. Should I do that now?If so, how much should I remove?

They are outside for some sun during the day, but we are still way to cold for them to be happy overnighting out.

Any info appreciated. Also have a mini tangerine in the same situation.

Those look like rooted cuttings rather than grafted plants. In citrus, it is the root stock that dictates the size of the top. If the plants you received are not grafted, those will become full size citrus trees. You can still grow them in pots, but you will have to re=pot them more often and do a lot more pruning. Normally, citrus do not need pruning other than to remove crossing branches, but since your trees will attempt to reach their standard size, you will have to do some pruning. For now, I would leave them alone. They should branch on theuir own. Apply some citrus fertilizer according to directions. Flying Dragon is usually used as the dwarfing root stock.

Grafted citrus trees are more expensive, but they are worth it. When I lived in Californis, I purchased most of my dwarf citrus trees from Four Winds Growers.
http://www.fourwindsgrowers.com/

Ortho and Sunset publish paperback books on citrus which you might find helpful. Also the California, Florida and Texas Cooperative Extension Services have online publications for the home grower.
http://aggie-horticulture.tamu.edu/extension/homefruit/citrus/citrus.html
http://www.ucce.ucdavis.edu/files/datastore/391-272.pdf
http://plantsbulbs.suite101.com/article.cfm/container_grown_lemons_in_texas
http://www.fourwindsgrowers.com/growing/containers.html
http://edis.ifas.ufl.edu/hs118
http://homeorchard.ucdavis.edu/Fruits_&_Nuts/Citrus/

Thank you SO much. Those are exactly the type of resources i needed!