I'm new to vectoring and I'm doing this one picture.

http://img26.imageshack.us/img26/1240/inkscapegah.png

I'm having a problem with the cactus here. What I did was create all the black and then on another layer, I made a green area surrounding the black and I got the difference of both the black and green. So if I hide the black lines, it would be the cactus colored in plus the surrounding green areas outside the lines. How would I get rid of the excess green without disturbing the green on the inside? I tried to break apart the green path and delete parts of it but I ended up deleting most of the green save for some at the top.
Any help would be appreciated.

Well in inkscape there away a bunch of way to do anything. And how you color those areas depend on how the black part of the cactus is construed. Is it all closed paths with fills? Or mixed? (I'm assuming the parts of the path you can see through are not exclusions because, if they were you already have fill those. You could use the bucket fill but hat would be a lot of time.) Best guess without knowing what kind of paths make up the cactus. Duplicate the black part of the cactus and put the duplicate on it's own layer to be neat. Call the layer say "temp". Make sure everything is un-grouped. (If there are any stoke only/open paths do a stoke to path under that path menu.) Hide and lock the other layers so you can see what you are doing. Select all the paths on the temp layer and do union under paths menu. Then do a break apart paths also under the paths menu. Then do a union again. You should have on big non-see-throw black cactus now. If there are open areas at the bottom of the cactus you want the green to show through add a path to cover. Then do the union, break apart, union again with the new paths, until it's all filled in the way you want. Change the full color of the black cactus to the green you want and turn off any stroke attribute from the stoke and fill menu. Unlock and unhide. Then move the new green cactus path back behind the black one. Delete the temp layer and the original green path.

Thanks for the response. I tried that but I ended up with just the big green field. And yeah, I think it's all closed filled paths.

I also tried differencing the black and green and I ended up with the green inner parts plus the green outside the black lines. Is there a way to cut up the paths in certain places like in red here: http://img40.imageshack.us/img40/8130/123yyb.jpg ? Any way I move the nodes just seems to make it wonkier so I'm wondering if it's even possible.

You're having issues because you're not working with a properly closed object (as in there are gaps which prevents things working as you expect). With selected, you'll notice a bunch of buttons on the tool control bar which will let you split nodes--these will let you chop up your path an join them in different ways.