Hmmm.......I've never considered the drainage holes to be overly large. But yes, I do think the soil media is the answer. Most commercial growers use a pretty textural bark-based potting mix that is not as likely to migrate through the holes as the more finely textured commercial bagged potting soils.

I'm in agreement with GG, the drainage holes aren't overly large. People have used different things to keep the potting medium inside, however, since the beginning of container culture.

As a former nursery grower, I can attest to the fact that very coarse textured mixes are the norm. Believe me, they aren't in the least bit cohesive.....just composed of larger particles.

I'd be curious to see one of these pots you're speaking of. Any chance of a picture?

Thanks. This is interesting.

The consumer containers I'm used to have one or two holes about 1/4" wide (like a pencil was pushed through) on bottom - minimal chance for media loss.

Most of the nursery pots I've purchased have multiple holes over 3/4" in diameter. One deeper type has 3"x1" openings slashed across the bottom. Super for drainage, but not the easiest to retain, say, a GW Container-Forum style "gritty" mix.

But nursery pots are so inexpensive, they are worth any extra effort.

Here are links to pics of couple I've actually purchased:

N. Pot 1

Deep Pot 1

N. Pot 2

The last photo shows pots I am most familiar with - the first does seem to have an abundance of drainage holes and I can see how media could easily filter out without some sort of barrier. Any kind of fine mesh or screening would work (eg. window screening) - something that allows water to move freely but is small enough to prevent the medium from falling out.

FWIW, I only use screening to cover the large drainage holes in glazed ceramic or terra cotta pots. I have never found the need for it in plastic nursery pots or even the more decorative plastic resin or fiberglass containers.

Those kinds of containers won't hold that grit based mix. As a matter of fact, that mix is based on what has been used for bonsai in the country for the past 20 or 30 years. Bonsai containers have very large holes that must be covered. HERE'S what is commonly used.

That plastic grid is perfect for covering the holes on the flat bottom of a more traditional container, but I think if you want to use nursery pots with the gritty mix you'll need to get creative. GG's suggestion of window screen is good, I used to use screen before I started using the grid.

Appreciate your sharing the knowledge, GG and rhizo. And yes I've used both screen and plastic canvas in these pots - and you are spot-on that it does take a little creativity to use mesh in those containers with a textured or irregular base, or side holes. Thanks again.

sam_md, thanks for the photo and type of mix used.

The picture is Anderson Tree bands, if you want to follow up on this. Warning: the flats have a finer mesh. They need the support of that finer mesh while the soil consolidates.