It really depends............depends on many things. For instance, if you have strong rooted plants like the swords then you wouldn't worry a bit when you siphon and vacuum the gravels around and near them. They wouldn't even flinch. Now, if you have delicate stem plants or foreground ones then you'd have to be more careful not to uproot them because their root systems are closer to the top; just right below the gravels.
For me, I don't even vacuum my tanks anymore because there is no need. I have too many plants and too few a fish. Instead, I do partial water changes every now and then, when I see the water level has decreased. In this case then, it would depend on how many plants you have; how dense your tank is. If you do have lots of fish and few plants and often see lots of crud and what not accumulate on the bottom then you will need to vacuum. You could by-pass this problem by putting the plants in pots. This of course, has to do with if you don't care about the whole aquascaping aesthetics.
Paul
For me, I don't even vacuum my tanks anymore because there is no need. I have too many plants and too few a fish. Instead, I do partial water changes every now and then, when I see the water level has decreased. In this case then, it would depend on how many plants you have; how dense your tank is. If you do have lots of fish and few plants and often see lots of crud and what not accumulate on the bottom then you will need to vacuum. You could by-pass this problem by putting the plants in pots. This of course, has to do with if you don't care about the whole aquascaping aesthetics.
Paul