Again, earthworms are good for the soil of any plant they're living in. But, if you're going to be using high levels of nutrients, or are prone to missing waterings, you'd be better off just getting some earthworm castings. Earthworms can get bundled up in the corners of pots sometimes, making it difficult to keep the little buggers alive & healthy. Don't add them to your soil unless you're sure you will be able to keep them happy...thereby keeping your plant happy.