Just bought two lightweight 'faux' whiskey barrels made out of some tough vinyl stuff. There are no drainage holes so before I ask hubby to drill them, what size and how many would be adequate?
They're for growing veggies (potatoes, sweet potatoes) but I figure you container folks would be good people to ask. Thanks!
As far as drainage is concerned, there is no advantage in having any more than 1 hole through the bottom at the deepest part of the container, though you can employ as many as you like. Rather than drill the hole, I would suggest you heat a piece of metal rod or a bolt anywhere between 3/8 - 1" and push/melt it through the bottom. Window (insect) screen works very well to cover the hole & contain the soil. There is an advantage to having the hole close to the circumference. It allows you to tip the container with the hole down to help drain excess water during prolonged periods of wet weather. This can be very helpful if you're using heavy, peat/compost/coir-based soils.
Let's say we have 2 identical containers filled with the same soil. We needn't be concerned over whether it takes 10 holes 30 seconds to drain all the water that will drain from a soil or 1 hole 3 minutes. The fact is, that at the moment the water stops draining from either container, the amount of water left in the soil will be the same as when the other container stops/stopped draining. If you have a soil that supports 3" of perched water, both containers will stop draining when the level of perched water reaches 3", whether there is 1 or 100 holes. How much water will drain from any given soil is not determined by the number of holes in the bottom of the pot; it's determined by the size of the particles that make up the medium.
Thanks, Al. That makes perfect sense to me. I guess I was not thinking in terms of the perched water table when I asked that question. I was just thinking that it would aid in drainage and that would be a good thing.
Thanks for the tips. Hubby just bought a new drill today so we had to use it, of course! I'll use your tip of a piece of screen over the holes, though, and I appreciate your walking me (us) through the draining process with respect to how many holes. It makes sense. I've read your wonderful info previously on perched water before, but hadn't applied it to this project.
I would just add this: in addition to at least one hole in the bottom, near the edge, as tapla suggests, it's wise also to cut or melt a notch (or make sure there's already such an opening) where the outside wall of the barrel meets the surface it will sit on. Without such an opening, it's possible for the bottom rim of the barrel to form an effective seal with that surface, which can keep water from draining properly --such a seal can can form from fine particles that initially drain out with the water.
well... one biger hole is better than a few smaller ones... less likely to clog with the fine particles that flow out with the draining water... I also use a pile of broken up styrofoam in the bottom... mounded over the holes instead of screening.. as there's less lieklyhood of it becomming clogged... the roots will also grow right into the styrofoam... searching into the tiny cracks and fizzures if the foam.. in search of additional water that has found it's way into them... anchoring the plant to the soil better then it just sitting there ...good for high winds..