I have several urn planters outside and the drainage hole never plugs up with soil, except for one container. It's a concrete planter and the hole is about a nickel size in diameter. While we've been having drought conditions in IL for a while, when it does rain a lot, the planter will flood. A local nursery told me to place newspaper across the hole to block the soil from plugging up the hole. Another told me to use weed screen fabric. I've used both but the hole still plugs up. I think I know why this container plugs up when the others don't but I wanted to run it by members here to see what you think. All the other containers sit on our blue stone walkway or patio. The concrete container, however, sits on soil. So I wonder when it rains a lot, maybe the soil in the hole has no where to go so it sits in the hole and plugs it up. If this is correct, then I can move it off of the ground and put it on our driveway. However, when I water the other containers, the water drains out from the bottom of the container and I don't see any residual soil drain with it. And I've never covered up the hole in these other containers with anything. I thought about maybe placing a sponge over the hole so the water will still drain through but not the soil. Thanks in advance for any advice!

Your assessment is right, that container doesn't drain because it sits directly on the soil. You could put plant risers or bricks under the edges to get it off the ground.

Don't use a sponge as that will block water from draining properly. I use a single layer of newspaper, screen or pieces of sand bag material to cover holes.

When a pot with a drain hole rests on the ground, the soil beneath the pot serves as a wick and helps to pull water from the pot. In fact, it can be so effective it will allow growers to use grow media more water-retentive than would normally be healthy. All that's need to take advantage of the earth's wicking ability is to make sure there is a soil bridge that makes a connection between the medium in the pot and the mineral soil below the pot. From the perspective of hydrology, when you set a conventional container planting on the ground with nothing blocking the drain hole, it terns a conventional container planting into a raised bed. This fact is what gave rise to the pot in pot, pot in socket, and pot in trench techniques of growing plants (mainly nursery stock). If you open up the drain hole and use the technique, it will be pretty hard to over-water, so well does it work. Raising the pot above the ground on feet or blocks ensures that any perched water the medium supports remains in the pot; whereas, placing the pot on the ground with a connection between the pot and the ground ensures all or nearly all of the perched water will be pulled from the pot by the earth's wicking action.

Alternately, you can make a hole in whatever is blocking the drain hole and push a wick up into the medium above the drain hole.







As long as the wick is in contact with the soil below the pot, it will work as well as the soil bridge.

The best way to establish this type of set-op is by leaving the drain hole(s) wide open and sinking the pot a little into the ground, but all that's required for it to work is that bridge between the grow medium and the soil below the pot.

Al

Thank you Lucy68 and Al for your insightful responses! 🙂

I think you're right about the cause being direct contact with the earth. I'd raise it above the soil with bricks or flat stone.

Incidentally, I cut a piece of burlap to fit over my pot drainage holes.

Thanks Engineeringtech! I think my theory is also correct because it's the only planter sitting on soil and the others have never had this issue. So I moved it onto the edge of our driveway so it's no longer it sitting on any soil. We are having a major drought and May was the driest in 150 years. But if we do get any downpours, I'm confident the new location will be successful in resolving this problem. Thanks again!

Before you commit, please try this experiment. Set the pot (or any pot) up on a platform so the drain hole is accessible. Water to beyond saturation, then wait until the pot stops draining. Once it's stopped, push a toothpick into the drain hole just far enough so it stays put. You'll immediately see the pot start to drain further because of the wicking action of a simple toothpick. Using an actual wick or a soil bridge between the grow medium and the soil between the pot will markedly increase drainage.

The scientific explanation for why this works is the wick or the soil bridge unites the soil below with the soil in the pot. This means the water in the pot is now at the top of a soil column of unlimited depth, which dramatically increases the gravitational flow potential of the water in your pot, which FORCES the water to move downward, out of the drain hole, and into the soil below. This isn't guesswork or an opinion. It is how the laws of physics/ hydrology work. I respect any decision you make - just trying to keep you from disappointment when improvement is so readily at hand. I won't comment again unless you have questions. Best luck.
Al

Thanks so much Al for your thoughtful response. I already moved the planter off the soil and after completely unplugging the clogged hole (actually, the tunnel going through the pedestal of the planter), I placed some landscape fabric to block the soil from going into the hole/tunnel and planted the flowers and watered thoroughly. The pot drained perfectly. I will definitely keep your information handy in case the problem returns as I understand the wicking bridge physics that you explained so well. Many thanks again!!