Choose a healthy plant that has no yellow or brown spots and no yellow, wilted or drooping leaves. Cut off a top portion of the plant measuring three to four inches long. Cut just above a set of leaves.
Cut an aerogarden grow sponge in half vertically, from top to bottom. If you're using AeroGarden's cloning gel, dip the plant's stem into the cloning gel. This is optional and your clones may grow well without the cloning gel, but the hormones contained in the cloning gel make successful cloning more likely.
Place the cutting in one half of the grow sponge and pinch the sides of the grow sponge around the plant's stem. Put the cutting and grow sponge in the AeroGarden.
Raise the AeroGarden's light hood as high as it will go and leave the lights off. Cloned plants need time to develop strong roots before they're exposed to light. Some AeroGardens have a button that allows you to program your garden for the type of plants you're growing. If yours has this function, set it to "salad greens."
Mist the cloned plants with water several times each day. When your plants have developed roots of at least 1cm long, add nutrients to your Aerogarden and turn on the lights.