Celery Soup extremely bland [closed]

Alliums

It doesn't matter if they are garlic, onions, leeks or shallots, but every online recipe I can see for croc-pot celery soup has at least one of them.

If you are trying to rescue a batch you have already made, I would suggest experimenting with adding onion power and/or garlic powder or puree, be sure to get powders, not salts though. Add a little at a time and give them time to become integrated in the soup to adjust the flavour, the result won't be instant, the powder needs to rehydrate before it fully releases its flavour.

The other element that I belatedly note is largely absent is fat. Fat carries flavours and adds satisfying mouth-feel to dishes. Again, most recipes I'm seeing online have more fat than the modest amount you will be getting from the milk. A couple of glugs of olive oil or a couple of table-spoons of butter will help bring out a richer flavour. https://www.thespruceeats.com/functions-of-fat-in-food-1328452

I'm kind of surprised that that recipe is coming out bland. One stock pot is meant to make about 500 ml of stock, so at the very least it should taste like, well, vegetable stock.

When you're looking at a recipe and it's too bland, the first thing to ask yourself is "what more". What flavor isn't coming through that you'd like to come through? Is some ingredient overpowering everything else? Are the flavors too simple, or too subtle?

If it doesn't taste brothy enough, and particularly if you're not used to non-meaty-tasting soups, you might want to try swapping one or both of the vegetable stock pots for chicken stock pots. You could alternatively try adding a third stock pot (but if you do that, don't add the salt).

If it tastes like just celery (a certain bitter astringency), reduce the celery to half. (That is a lot of celery in the original recipe.) I know it sounds counterintuitive, but decreasing an ingredient can increase the taste if it helps balance the flavors and let subtle ones come through.

If you'd like it to taste more herb-y, thyme would be the normal approach. 1/4 tsp of dried thyme, or 2 sprigs of fresh thyme, added at the start.

For a more vegetable-y taste, another option would be adding leeks... at the start, thinly slice the white and light green parts of one leek, then saute over medium heat for 5 minutes with 2 tbsp of butter, then put the mixture in the slow cooker and go on with the soup. That pulls the recipe closer to a classic leek-and-potato soup, though, which is maybe not what you're looking for.