How big does the hole in the pot need to be?
 

My father gave me a glass vase that he had drilled to use as a semi hydro pot. It is really pretty but the hole is not as big as the ones in my plastic pots and there is only one of them. Is this going to be a problem? How big does the hole need to be? And if there is only one does that cause a problem with lack of air circulation?

The holes in the sidewall of the pot do very little to affect air flow, and in fact, they are not intended to do that and should not provide very much anyway.

I find that two, 6 mm holes, placed as close together as possible without intersecting, is the best case.

If they are larger, or there are too many holes, the evaporation from them cancels out the wicking rate of the medium., and it also makes it tough to fill the pot rapidly to allow it to flush and saturate the medium.

I like two holes, as sometimes a LECA ball nestles up against a hole and nearly blocks it. If that is the case, and that second hole is very close, that piece of LECA prevents another one from blocking the other hole.

Thanks so much for your quick response. That is very helpful. The hole is a little under 6 mm but I think maybe it will do. I see what you mean about two being better the in case the hole gets blocked.

Another question: How much does the shape of the pot matter? This vase is similar to a standard flower pot but is a little wider at the top. Is it important for the pot to be fairly straight up and down for the media to wick correctly?

---------- Post added at 06:59 PM ---------- Previous post was at 06:57 PM ----------

I'm using Hydroton clay pellets as media by the way.

Think of the two counter-acting processes: wicking and evaporation.

The ability of the LECA to wick is a fixed physical property of the brand of material used. It will, in all cases, absorb and transfer water to the next pellets as well as it can - no faster, and no slower.

Evaporation, on the other hand, is dependent upon many factors, and will vary with surface area, temperature, humidity, air movement, and light levels (warming the top surface).

If you take a one-pellet-thick "slice" of the pot, your larger-diameter "top slice" is being fed by a smaller-diameter "slice" below it, so the evaporation may be faster than the wicking can keep up with.

From a practical perspective, don't worry about it. That's less of an impact than your growing conditions.

By the way, if you see that a pellet has slowed the drainage from the pot, just poke it with a stick or wire stake.

I think the vase should work fine then. Thanks for the input.

By the way Ray, it was your site that got me into trying semi hydro a few years back. I love it, makes growing orchids so easy.