Unless you know your soil is deficient because you've had it tested by an extension service, I would not waste my money. Do the phlox look starved for "something?" Keep them pinched and "thrifty" remove the thinnest stalks so air circulates well; monitor closely for mildew and treat before you see any (make a spray 1 pt milk, 9 parts water thank you to those who have reminded us of this cheap, non chemical intervention)

and I hope they do well for you.

If you feel you must do something, put a light top dressing of compost around them, keeping the top dressing a few inches away from the stalks. Water properly. Your phlox will be fine.

Great thanks. I just planted 2 glamour girls and did add compost. I don't know what my plants would do without this website. Everyone is so helpful.

in mother earth.. there is little of anything that needs constant feeding ... they are plants.. not children ...

if you suspect there is something wrong with your soil... then have a soil test done.. and properly amend the soil ...

the only place fert is usually necessary... is in pots.. when as you water.. you wash nutrients out of the pot .. so there is a need to replace such ...

and generally .... any balanced fert is good enough for all the plants.. you dont need to pay extra for special formulations for certain plants ... most of all that is marketing mumbo jumbo created to separate you from your money ...

in my world.. warped as it is.. skip spending on fert.. AND BUY MORE PLANTS ... focus.. lol ...

ken

Glamour Girl is a good phlox. Sturdy. I hope I remember correctly is was mildew free for me.