If you haven't already, I highly, highly, highly recommend watching Brandon Sanderson's videos on writing. He teaches a course at BYU on creative writing and has a website where they post his lectures on youtube. If you google "Brandon Sanderson Write About Dragons 2013" you'll find the website and all the lectures. Anyways, he talks about this in one of the lectures and suggests trying each style. Many authors, from what I understand, aren't just one or the other - they take elements of each and find what works best for them.
Personally, I don't outline like an architect, but I do have an ending in mind as well as a basic game plan in place before I start. For my current serial, I know exactly how it's going to end, I know how many arcs it will be, and I know more or less exactly what's going to happen in each arc leading up to the conclusion. Did I write all of it down? Not really. I knew the ending starting out and a few key scenes that I knew I wanted to include and then as I started to write, more and more ideas came to me to fill in the gaps. Does that mean the story will turn out exactly like I thought? Nah, as I'm writing things often change, but the general plot outline is there.
If there's one thing I think can benefit a gardner, it's this: know where you're going. If you write by the hip, it's great and all, but sometimes you just end up spinning your wheels and you'll have these arcs/books where nothing really happens. If you have an endgame in mind, it really helps streamline everything. This way, when you're "gardening," you're doing so with a purpose.
Just my 2 cents.
Edit: No two people have the exact same writing style. You just have to experiment and find what works for you. For me, I tried outlining (writing everything down) and found that it tended to kill my drive to write. I also found that so much would change during that first draft (new ideas would surface, subplots, etc) that it almost wasn't worth it for me to take so much time outlining.