This plant-care website writes
In the context of plant care, usually most plants within the same genus need the same environmental conditions suitable for plant growth. If the genus of a plant is known, the information can be used to apply the appropriate levels of plant care.
I'm wondering if this is true in general. A more general question would be, if I know that two species are in the same genus, what phenotypical similarities will they have?
So far I've only found that genus classification is based on genetic similarity, but that doesn't say anything about what phenotypical similarities there may be between different species in the same genus.