Molasses (the darkest one, 'Black Strap') is high in Iron and is good for plants. Before fertilizers were so easy to come by, some gardeners used Molasses to add Iron to their watering cans for a quick boost to plants. If you didn't live in the country with easy access to stuff from farms, you had to be creative.
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I just read another post here and see that it contains other goodies...I never have actually read the label or used it for my plants. It is also good in Pumpkin pie.
With modern fertilizers abundant, many of these older tricks are no longer needed for gardening. I would just go with a good fertilizer that has everything added.