According to the Gardener's Supply Company, seedlings become "leggy" when they do not receive enough hours of light or too much nitrogen in the soil. This term describes tall, spindly and unstable stalks and an overall malnourished look. Broccoli is one of many vegetables that exhibits leggy characteristics when it doesn't get enough light, and it is sometimes difficult to revive the plant from this state. If your broccoli seedlings have a long, thin stem or have fallen over, there is a chance of saving them if they have not withered too much, are white in color or have black spots on them.
Whether your broccoli sprouts are indoors or in an outside plot, you will need to give them more light if you hope to salvage them. Move indoor seedlings to south-facing windows to give them more hours of sun, or set up a small fluorescent light to help them grow before moving them outdoors. Transplant outdoor broccoli plants to a sunnier location in your garden, taking care not to rip the fragile shoots when uprooting them.
Amend the soil around your leggy seedlings to reduce the amount of nitrogen, which can cause plants to produce weak sprouts. Feed leggy broccoli with fertilizer high in phosphorous and low in nitrogen, and water regularly to dissipate the element.
Broccoli seedlings that are so leggy they have fallen over can be saved by being cut back. Cut the young plant back to its first true leaves, cover the roots and stem with supplemental top soil, and stake it if necessary.
Continue supporting your broccoli seedlings until they are mature and sturdy enough to go without such attentive care. Check their stake holdings every few days to make sure the seedlings are receiving the best system of support, and make sure the soil is moist, but not flooded or over saturated. Young broccoli plants benefit from a nitrogen-based fertilizer, once it has recovered from its "leggy" symptoms, and they require adequate sun and water, especially as the edible flower heads develop.