I start to fertilize my seedlings when they have true leaves. I start with half strength water soluable fertilizer, and I apply it with an empty, clean dish detergent bottle. I can 'apply' the fertilizer at soil level, and I am sure the fertilizer is getting to the roots. (This for seedlings in flats, or containers.)

I don't know about fertilizer on tomato leaves, but if it is water soluable,(Miracle Grow, Peters, etc.) I don't see the harm. Many fertilizers are beneficial when used as a foliage spray. Seaweed is one that comes to mind.

Janie

I just got this fertilizer called Plantea yesterday and it is recommended as a foliar spray for young seedlings. The main ingredient is seaweed (kelp, actually). I applied it last night and today some of my babies that were a little wilted have straightened right back up. I did read that plants absorb much more of the nutrients through their leaves so when you use any fertilizer as a foliar sray it should be very dilute. Maybe that is why you heard not to get it on the leaves, full strength probably wouldn't be a good idea.

Taste: im wondering if your underwatering. I don't think fertilizer would have that affect. I water mine and wait for the soil to dry 2-3 days and then water again. I think this is about optimal.

I did read that plants absorb much more of the nutrients through their leaves That's largely a propaganda put about by the promoters of certain products. I try to avoid leaving fertiliser on the leaves of plants, seedlings or adult, it can potentially be damaging in strong sunlight. But then fertiliser at the roots can also be damaging in the wrong conditions.

ncage,
I actually thought they were wilted from too much water. I bottom water thru capillary matting so they are always moist. But they really perked up so I am happy. I should mention it was only my stocks, not all of my seedlings.

shrubs,
The new fertilizer I am using is incredibly mild and I don't think you could damage a plant with it if you tried. Also, in this case I don't think the foliar spray could be propaganda primarily because when you apply the fertilizer to the roots they instruct you to apply it directly as brewed. One tea bag make 2 cups so you would be going through a lot of tea. However, for the spray you add 1 Tablespoon per quart of water. 1 or 2 teabags could last me all season and I won't be buying anymore for a few years.

Here is a link that might be useful: tea fertilizer

my only comment here is to reference Horst Marschner's
Mineral Nutrition of Higher Plants,2nd Edition. It is an extraordinary loss that the world has lost such a profound plant scientist.