No way to know for sure unless someone just happened to have personal experience with the exact same mix.

The worm castings wouldn't be so much a threat to the seeds IMO but would to the young seedlings. Just emerging seedlings don't need and are very intolerant of supplemental fertilizers. Nitrogen especially, in just about any form, can kill them off before they even have time to straighten up their stems.

As the age and develop true leaves - say 2 sets - their need for them increases as does their tolerance.

So personally I'd leave out the castings. Save them for adding to your mix come the true leaf transplanting time since the plants won;t be able to remain in the coir mix for long.

Dave

While I never add fertilizer to my seed mix, for your tomatoes and peppers, both fast germinating and growing, using 10% castings, which are potent, but slow, I think you will be alright. For other seeds a would not do it. Al

Thanks folks. I did not get your answers in time and planted the seeds. I will report back as to how they grow. I did a little poking around on that web thing and some of what I read said that with worm castings, some have noticed a marked improvement in germination rates. I will let everyone know what I find out. By the way, they are my own castings so I know what went into them.

rich

How did your plants fare Rich? I've just sown some seeds with a little worm castings added beneath each one. I am eager to see the results, if any.
PK