Top panel: stellar metallicity vs. semimajor axis of planets around evolved (giants and subgiants). Planets around giants are indicated by red squares and planets in subgiants by blue triangles. Black dashed line at 0.5 UA, indicates an observational limit for which none planet around giants has been detected. Middle and bottom panels: [Fe/H] vs. semimajor axis for planets around subgiants and giants, respectively. Here, the control samples are represented with black crosses. The magenta dashed line on the bottom panel represents the critical metalliticy for planet formation in the core accretion model, see Sect. 6.3 for details.