Like with the Strolling Saplings, the drops from these guys vary based on what region you kill them in. So yes, they do drop all three kinds of seed. You just have to be in the right zone to get the drops.
I was fighting a Walking Tree and one of these linked with the tree. I almost died because of this but thanks to Hundred Fists, I lived. Be careful of this...
These do not drop Vegetable Seeds. They -do- drop Herb Seeds and Grain Seeds. You can 'Steal' Herb Seeds from them (and pretty much any 'bulb'/'seedling').
They DEFINATELY drop vege seeds. I used to farm the ones in thiene for the seeds but moved here as the drop rates a little higher and i take em in 2 shots now. I farm the vege and herb seeds they drop. Go for a pretty penny on pheonix.
They do not however drop grain seeds from my experience. I have probably killed 300 of these and have never recieved a sack of grain seeds. They only ones who drop grain from my experience are the ones near where leaping lizzy spawns. But grains seeds r a waste so i don't even bother
They drop grain seeds like mad near Bastok in the North and South Gustaberg regions. And grain seeds are not as much of a "waste" as you think if you are at all into gardening.
At Level 15 in Meriphataud Mountains, these conned mostly even and tough, and were very easy to exp chain in a small group (2 or 3 people). It was very easy to chain 2 or 3 of these in a row using TP and Skill Chains. Around Level 16, these are mostly even and decent cons, with the occasional tough con one.