Question
I have a Ginko in Southern California, not too far inland from the coast (which may be pushing their range).

For some reason it isn't happy.  It has new growth, but it isn't blossoming like my other plants.  It seems very retarded.

What kind of fertilizer do they like?  Is it okay to give ginkos fertilizer designed for sago palms since ginkos share an ancient lineage with cycads?

Can I give it epsom salts (for magnesium) like a sago palm?

Answer
Yes you can give them same fertilizer (fertilizer is not plant specific to the point where it is formulated for specific plants, but more on a general basis such as flowering plants, fruiting plants, trees, shrubs, flowers, etc). Epsom salt is ok, too.

Be advised, however, that fertilizing a stressed plant can cause more problems. Before fertilizing I would recommend you try to find out what the problem is.

Light green, limited foliage, overall yellowing of leaves (especially old leaves) and lack of branching is often signs of nitrogen nutrient deficiency.