Air pruning

I want to know if I can make air pruning pots out of small styrofoam cups. My plan is to cut out the bottom part of the cup, attach a net/mesh on the bottom part to prevent soil from just passing through and also puncture small holes on the sides with a knife. Would such a cup/pot air prune the roots of my plants?

The way I understand air pruning pots, just poking holes will not be enough. The pots have a special shape to lead the roots to those holes, otherwise they would just run in circles and bypass the openings. I would strongly discourage you to use styrofoam cups anyway. Too much ick.

Air pruning requires, as Philipp mentioned, the roots to grow in a more natural (spreading instead of circling) way, this leads then to grow through the container for the growing soil and then the tips dry out and die.

While it is a novel method of keeping roots shortened and thus the plant smaller, you still need to come along and snip off the dead, exposed ends.
What it does is a type of Bonsai.

Philipp Mueller wrote:The way I understand air pruning pots, just poking holes will not be enough. The pots have a special shape to lead the roots to those holes, otherwise they would just run in circles and bypass the openings. I would strongly discourage you to use styrofoam cups anyway. Too much ick.

too much ick, what is that?

I think that's short for "toxic ick".  On permies.com we tend to favor things that use natural stuff.  So styrofoam, and the process that mines and produces it, is not held in the highest regard.  Now if you were taking used styrofoam cups and getting another use out of them before they enter the waste stream, that would be awesome.

Welcome to Permies by the way.  I haven't tried air pruning yet myself.  I can't even get hardwood propagation working  Here's a video by Edible Acres on how he builds air pruning beds.  It doens't have guides for the roots either so maybe there is hope yet...

I made 2 with landscape cloth and 2 with nylon windows screen.
MANY holes 2 1/2 inch diameter.
If air doesn't stop the root travel then sunlight should (on the one with nylon screen).
We have the ones with landscape fabric but the wife's has the two with nylon screen.

All are hugel style too (some wood pieces on the bottom of the 5 gal buckets.

will be interesting to see how things work out IF the wife's friend doesn't use the poisoned tap water the city supplies. We have rainwater collection (35 gal trash can).

Edit: additionally if the roots do circle at least there will be a lot more oxygen to the soil medium.
Still can win either way.

When training a new tree as bonsai I will often plant it in a colander to air prune roots. The shape is ideal for developing a round & wide root spread, while also encouraging ramification of the feeder roots.
I generally grow my pre-bonsai like that for a couple of years to develop the roots, then will plant the colander halfway deep in the ground and let the feeder roots grow through the holes for a year or two so the tree can access the nutrients in the soil, which helps develop a wide trunk. Once I have a good root system developed and a nice base & trunk started I'll remove it from the colander to a growing box while I develop the branch structure over a few years. Some people use the filter baskets for ponds in the same manner.
I suspect a styrofoam cup wouldn't work well is due to it being a deep container instead of a wide one. From my observations, it seems the feeder roots prefer grow out, instead of down, which is why pot-bound roots *mostly* grow in a circle within the pot, instead of all growing straight down through the drainage holes.