A friend of mine asked me about putting worms in potted plants. Here is what I sent him.
"I wouldn't do it. The thing you are after with the earthworms are their castings. They also loosen the soil but if you are doing pots your soil will be aerated. Just change out the soil each time you re-plant. What I would do is just start a worm composter. You can buy one or build one. I built my own. Then I bought a pound of red wigglers. After about 4 months they double. They eat half their weight of your compostable stuff. That includes paper and paper products - napkins. 1 lb = 1/2lb of food per DAY. The thing doesn't smell in fact it smells like moist earth. They really do the trick. Then you can add that stuff in your potting mix or you can take it and dissolve it in a watering can and make worm tea - sounds gross I know but it is like all natural steroids for your plants. If you start one but are worried about waiting 2 months to get a supply you can buy worm castings from nurseries. That would hold you over till you started to get some for free. Send me some pics when you get it started. Also if you want to build your own worm bin I can help you out."
Then I found Growing Power's website and sent him another email.
"So I have to amend my previous posting.http://www.growingpower.org/growing.htm. This website is an urban farm and they advocate putting a handful of worms into each pot. They produce a ton of food and are going strong so I would have to say they know what they are talking about. If you want to be creative try two pots - one with and one without and see which does better. Just plant the same thing in each.
Let me know what you decide."
The jury is out for me on this one. There are a lot of variables at play here. Do they have a high turnover on the plants potted and are constantly adding new soil mixture? They use mostly compost in their pots so does this make it ok? Is it dependent on the size of the pot? Most of the stuff I'm reading on the internet is off of forums and there seems to be a resounding negative to doing this. I have to admit that my first reaction of saying NO was because "We've never done it that way" mentality.
OK, let's look at this logically:
1. Worms are beneficial in the garden because they eat organic material and deposit castings. They help build soil.
2. The mucus they do excreet helps soil to clump together which helps in water retention.
3. They aerate the soil, loosening it up for roots to grow deep in search of water.
4. The micro-organisms associated with the worms help digest minerals and place them into a form that plants use.
5. The one bad comment is that their burrowing allows water to run out of the plant too fast. But if you treat your potted plant's soil like you would if you had a huge garden then you shouldn't have this problem. Basically, mulch your pots to help with evaporation and you won't have to drench them with water which would add to compacting the soil over time.
I'm ammending my first opinion and saying go for it. I used to treat my pots like they were their own entity and somehow different then if I was growing in a field. They are not. Building good soil is the same whether its in a field or in a pot. If anyone has experience with this I'd love to hear about it.