Citrus is not tolerant of the considerable temperature swings of spring in the northeast and needs a warmer night temperature. I suggest that you wait until it is consistently in the 50’s at night before making the move outdoors and the day temps are consistently in the 60s. In the NYC area May 15 is usually okay to set out plants. Then go through an acclimation process of taking your tree in during the night and returning it to the outdoors in the daytime. Do this over a week's time and your citrus tree should be acclimated.

Continue to watch the weather forecast! If the forecast says it is going to get really cold on a given night, take them back inside or better yet, drape them with burlap or a sheet loosely to give them a little protection. This should work since the cold period will probably only be for a day or two.

Early spring is a good time to prune your plant, before they start to really become active. 

Hope this is helpful.

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Courtesy of the NYBG Plant Information Service

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