Gorvin you rawk. I don't totally get how to do that with Nature form, jump *around* your briar when it's poking out horizontally? do you try and aim it slightly pointing up and jump straight off your lower briar board? I get that much in principle, but then what, you are now to far 'in' to jump to a straight out horizontal briar. I'm totally down with being all spidey with Nature, just don't get how. regardless, I bow to your obsessive exploratory glitchyness 
Actually, I didn't fire off the horizontal briars until after I had jumped. What I did was to jump up off of the first briar, then fire a briar into the wall while I was in mid air and end up landing on top of it. It had to be timed right so that the seed would land and sprout out after I had passed over the spot it would grow at.
There are two briars in the screenshot because beforehand I landed on the *tip* of a briar higher up, and by clinging on to the tip at an angle, I would have only been able to jump away from the wall. So I shot 3 more briar seeds, which caused the briar I was on to retract, pulling me in towards the wall and dropping me down to the briars I planted underneath it.