Posted: 22/05/2015 at 16:30
Yes...I assume its the dried, bagged concentrated stuff.
the rudbeckias, are they the annual or perennial type? For the perennials I would trench in plenty of garden compost or bulky manures in the autumn.
However, mix a few handsfull of dried manure with your soil before returning it to the planting site. Keep area well watered during summer