JKL wrote:

I grew an avocado from seed - in my ignorance I didn't pinch it back
when young. Now it is 4-5 feet tall and very spindly, beginning to bow
over.

Can this plant be cut back to encourage bushing out? How far back can
I cut it?
Will it need fertilizing?

Thanks

I did the same thing and finally got the courage to take the top 12"
off. Now I have a 4' avacado with three new branches on top covered in
leaves.

If you're main trunk is spindly and won't support it's own weight try
giving the tree a bit of a jiggle when you walk by it. When a tree is
outside it is stimulated by the wind to stiffen it's trunk. When we
grow them inside they aren't stimulated and get weak.

Good luck,