Confusion in understanding growing instructions
I'm getting quite confused about growing instructions for plants such as Mexican fleabane. It thrives in cracks in paving and walls. And yet the RHS say we must grow it in fertile soil that does not dry out. I see this kind of description all over the place.
Here baby's tears is said to require moist soil, yet to my knowledge it's quite happy on gravel and paving cracks.
I'm also confused about instructions like 'moist but well-drained'. How can soil really be both. Surely if something is permanently damp it's holding water and therefore not drained.
This poppy, they state, grows well on chalky and sandy soil and requires 'deep, fertile soil'. Surely this is a contradiction in terms. Isn't sandy poor synonymous with being poor?
Ox eye daisies - moist, fertile soil such as sand.
Is it a question of situations where plants will grow if forced versus their ideal growing conditions? Do all these plants what rich fertile soil really but will survive on sand if they have to?