I'm master 8 farming with 10 old moon fences. 8 of those fences have magic hot peppers and 2 are special onion and they are seperated so each crop is in it's ideal climate.

Sometimes I go 1 or 2 days without a mole. Today I got 3 moles in a row but now that you mention it I have never gotten a mole on my onion farms.  I just assumed magic seeds have better chances at moles and I have more magic plots so the rng is in their favor... Now I'm going to pay more attention *glares at onions*

*Update*

Just got a mole on my onion farms so it really is just poor RNG you haven't been getting any =/

Ty for the reply but you said Special Onion, I have gotten moles from them as well.  Only High Quality Onions have never poped (8 days in a row).  I have changed to other seeds and getting moles every day.

+1

I use old moon fences x 10. I breed and harvest magical onions. I get at least 1 mole to spawn each day.