I don't....I top dress with composted manure before I plant and that's it.
Linda c

About a month after planting as bedding plants ...I give mine a quick Miracle Grow shower every other Saturday until mid Sept.

Pete in Iowa

Are you planting them the same place each year? The lady from our local greenhouse told me to put a dose of lime a few weeks before planting them.. The repeated planting drains the soil.. I do this each year and it works wonders...

Susie

You could add some compost to the soil and some manure. That should help the soil and there should be microbs in it as well.