The origin of the seaweed used is from the Gaspesian peninsula in Quebec, and it says the dilution varies; I suggest you still add water ( empty contents in a big basin and put half water in the container and add to the seaweed in the basin and funnel it back to the container. You will have half a bottle extra of diluted seaweed. Better be safe. That is why you are having that foul smell. It is still heavily concentrated I beleive.
I see what you mean about that product. It looks like it's supposed to be used as is. I think it would be OK to spray on your orchids right out of the bottle. Seaweed is not a strong substance and I've never heard of it burning plants or roots. Just use a little at first until you see how they react. Seaweed is great to use in the spring because it encourages root growth.
Wow! Thank you so much for the loads of great information guys. I am now curious why my seaweed extract stinks so much. Maybe it just gone bad in the store and i need to go buy new one and smell it right there? Do you keep it refrigerated? Store has them just on the shelves, even exposed to sun in some places.
I also bought liquid seaweed from Rona. Mine was in a concentrate form (Marinis). Mine was pretty smelly too. I'd be curious to know about the 'smell' as well.
If a product says it's okay for roses, then it's okay for orchids. Most products don't mention orchids as I guess they're considered too exotic for the average application.