A cutting off a tomato plant will root easily in a cup of water. That makes it easy to keep your indoor tomatoes, AND start some for the outdoor garden! Simply trim a new, growing tip, about 3 inches long, off the newest growth of a tomato in your AeroGarden. Drop that stem into a glass of water, with about 1 inch submerged. Trim off any leaves that would be submerged, but make sure to leave some leaves on your cutting. Place the glass in a window (but not where it gets hot, direct light) and keep the water topped up.
Within days, you should see small white roots emerge from the stem of the tomato cutting. After about two weeks, you can transplant the cutting into high quality potting soil. Keep it evenly moist. You can move it to a sunnier spot now. After a few days, you can start to harden off your tomato cutting outdoors on a sheltered porch or patio. Let it sit out for an hour or two more every day. Move it inside if conditions get too cold or rough.
When the cutting is well-hardened, you can transplant to the outdoor garden or container. Water especially well at first! By this time, your indoor tomato will have grown back to replace the cutting you took. At the end of the summer, you can take a cutting from your outdoor tomato and move it back into your AeroGarden. But that will be the subject of a different tip!