Yes but they tend to tolerate some alkalinity. When your soil becomes too alkaline though, the leaves show signs of iron chlorosis in which the leaves turn light green or yellow while the leaf veins remain dark green. If this happens, amend the soil with any of these: greensand, garden sulphur, aluminum sulphate, ferrous sulfate or iron sulfate, or any of the liquid iron-chelated compounds sold at most nurseries. Note that this is indicative of permanent soil pH "problems" and the soil should be amended basically forever, on a schedule (see the product label) because the soil eventually reverts to alkaline if not amended on a regular basis. The liquid iron-chelated amendments resolve the problem slightly faster than the others.