Hydroponic milkweed cupsMobile hydroponic milkweed cups can be taken out of the hydroponic nutrient system and placed into a container with rocks in the surrounding space, and fill partially with water, to below the top of the rocks. Your plants will stay fresh and good eating for the caterpillars, or, use these plants inside containment structures for breeders to lay eggs on. Simply remove the plants and replace with new ones, and collect the eggs. Cut back the plant and return it to the hydroponic system for regrowth.