When I posted on GW I do remember Carolyn and someone else mentioning GA-3 could possibly be harmful to the seed it's used on.
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Jeff, no it's not harmful to the tomato seeds but what you end up getting are hormone induced tall lanky stupid looking seedlings.
That's why I and others tried varying the concentration of GA with something like potassium nitrate, also known to sometimes help wake up old seed.
But adding the Knitrate made no difference and I can't suggest using GA on tomato seed b'c it did no
better than a good water soak in waking up old seeds and when the seeds were treated, those that did appear were lanky.
having tried a lot of stuff I still think that a good o'n soak with a pinch of blue stuff works best.
And it makes a difference if you have seeds with NO germination rather than trying to up the germination rate. If the latter it's just easier to double/triple sow seeds IMO.