Bitter melon is an attractive rambling vine native to tropical Africa, Asia and Northern Australia. It produces lacy foliage and pretty yellow or white flowers, which are followed by the unusual looking, bumpy, orange or green skinned fruits. The cooked fruit and young greens are eaten in China, the Philippines and other parts of Asia cooked in stews and curries. The raw fruit is quite bitter because it contains quinine and must be fully cooked before being eaten. Established bitter melons produce abundant seeds, which are relished by birds in spite of their toxicity. It's usually very easy to find young seedlings in the vicinity of a mature vine.
Find mature melons that have exploded open on the vine, exposing the bright red seeds. Often the discarded skin of the melon will be tangled in the vine or on the ground below the plant. As soon as you notice this, watch the ground near the vine for sprouting seeds. Bitter melon seeds will germinate within 2 to 3 weeks in warm weather.
Check to see if the seedlings have two rounded, highly toothed leaves on opposite sides of the stem. At this stage, new bitter melon seedlings look very much like young cucumber vines.
Look for the second set of leaves emerging from the growing tip, which are the plant's true leaves. These leaves will have the same deeply lobed appearance as leaves of the parent plant. If you see these, the seedlings will almost certainly be bitter melon since the five-lobed leaf form is quite distinctive.