I know this isn't exactly what you're asking but hopefully it will be helpful.
The fastest and easiest way to get lots of King Parsley that I know of is by planting what you have. You only need 1 to end up with more than you can plant. They drop extra seeds so frequently I started with just 1 and ended up with a plot really quickly. The more you have the more extra seeds you get too, so it might feel a little slow to start off with but you will soon be getting lots, too many to plant. This is why one of my accounts has never had to farm for KP seeds but regularly feeds spares to pets.
My second account happened to get some from fishing chests in the Acropolis house (you can go there through castle tours if you don't own one). I winnow ice and there is almost always a chest there. I was fishing for shining scales and KP seeds were frequently in the chests.
The Great Moodha Statue also drops them so popping in on him and seeing what he has for you might be worth it - it's a quick, easy option if you get lucky
Good luck....and plant what you have as soon as you have any!
King Parsley can be found much easier than you might assume.
In addition to the crown shop (for 750 crowns), I've had my best results trying to gain the seed by doing a couple runs through Mirror Lake.
As Victoria hinted, the plant re-seeds pretty often. Being able to gain one can see your bag quickly fill up. So highly suggest, if in the attempt you're unable to gain it as drops, trying buying it for crowns.
You can also try the Road Warrior's Pack.
The Earth Elemental in the Plaza of Conquest also drops it. Ivan Soulsinger does too. Avalance as well. The Collector too.
Good Luck!
I'll also add, don't count on the plant dropping ambers at harvest though! You'll have much better luck farming for the actual reagent as many of us have unfortunately concluded.
