Pontinella bushes grow but wont bloom. Sandy acid soil feed them 2 times a year
Wexford County Michigan
Potentilla bushes bloom best with full sun...that means eight uninterrupted, unblocked hours of sun. How much full sun do they receive?
Sandy soil can mean that the soil is not holding moisture successfully enough and there is enough moisture for growth but not flowers. It helps if soil is mulched with three inches of woodchips. Are you checking soil moisture? How do you water?
Acidic soil can be a problem if the pH is not corrected. If the pH is too low, the plants cannot get the nutrients that are already in the soil because the low pH blocks it. How low is it? Is this an MSU soil test or a home version? Have you done anything to correct the acidic soil? What? Even if you are fertilizing them, the pH can block that, too. If you want to purchase a soil test self-mailer, you can buy one for $25 online at: www.msusoiltest.com
Potentilla do best with the removal of up to one-third of the oldest canes each year in the early spring. That gets new shoots to come up and add vigor to the plants. Are you pruning these plants? It is possible to prune off potential flower buds.
It comes down to three things: light, soil and pruning. If I have an answer to the questions, I have a better chance of giving you an answer. Or there may be enough information here for you to know. This is a very easy simple bush to get to bloom so it is almost impossible to buy three duds.