Annuals that prefer a higher pH (over 7, alkaline) include….

Geraniums (pelargonium), celosia and marigolds. Annuals that like acid soil (pH lower than 7) are petunias (shown), pansies and bacopa. If you have a bed with both geraniums and petunias and the geraniums are doing better, one cause may be that the pH is shifting to alkaline (or vice versa).