Bird seed is sterilized, it should make excellent organic food for your plants.

Sorry Drew. What I have experienced this spring/summer tell me that isn't true.
In my preliminary spin around the interwebs, I found that there seem to be two camps: "Birdseed is sterilized, period, full stop. (Those growing things are coming from somewhere else)" and "I have a jungle under the birdfeeder (that I'm getting mighty tired of chopping down)"
Even if bird feed is irradiated, or otherwise sterilized, there's enough of a margin of error that some of the seed is going to remain viable. And that margin of error seed grew quite nicely in my organic soil, stealing nutrients from my intended summer harvest.

You'll need to google for images of the plants you planted. But it really isn't going to hurt anything to wait until your plants are big enough that it'll become pretty obvious what is and isn't a weed.

Once that happens, pick up some cheap cedar mulch from home depot or something (make sure it's not dyed, whatever you get) and mulch around your plants. It'll cut way way down on volunteer bird seed, and make it easier to pull if it does get settled in. It'll also even out the soil temp and moisture in your containers.

It may depend what company is selling the seeds, or if they are buying bulk seed and using it for bird seed. Yeah mulch sounds like a good idea. I get weeds though all the time in every pot, and every raised bed or anywhere I plant. The last two years stinging nettle has appeared in my garden. I never seen it before, ever! Anyway it got me three times, now I know exactly what it looks like. It was a very painful lesson!

Drew, I use flattened cardboard boxes as weed barrier under my mulch. In fact I started using this type of mulch to keep the cardboard from blowing around, LOL! It has turned out to be a very effective combination. I have been doing this (cardboard as weedblock) for at least 20 or 25 years now, I'm actually not sure any more. But a very very long time.

The cardboard will break down over time. Keep it back from the plants so any rain water can easily get into the soil Wet the cardboard down before laying it on your bed, which you have also watered so that it is moist but not soggy. You can lay it down in blocks at the start of the season, then when it comes time to plant, just cut a hole in the cardboard out to the eventual drip line, plant your plant, and replace the mulch (which you had to pull back from the planting area to expose the cardboard).

Every couple of years, lay down more cardboard as the old stuff breaks down. Worms will be busily pulling it down into the soil. The cardboard and mulch will cool the soil and help to keep the moisture even, which encourages all the microflora and fauna and the earthworms. You will never have to disturb your soil. Few weeds will be able to poke up and those will be easier to pull because of the mulch - they will be less firmly rooted in the loose fluffy soil the earthworms are making for you.

If its a new bed, I work as much peat moss as seems appropriate into the soil and then lay down the cardboard. If other additives need to be added you can do that as necessary. pH has never been a problem for me - yet. Mostly I've struggled with heavy clay soils, which I have found it easiest to let the worms do my work for me. Here I have very sandy gritty soil which is hard to impossible to keep evenly moist in this arid climate - but the cardboard + mulch make it seem like black gold, LOL!

I don't even bother with cover crops any more. This is the quickest easiest way to improve soil I've ever used, and it makes gardening a lot easier. I put everything on drip irrigation but I can water by hand if I need to. Even here in the arid West, the soil is moist all the time, as compared to non-mulching gardeners in the area who battle a dust storm every time the wind kicks up. Sometimes I only have to water once a week, twice at most.

If the old cardboard bothers you, you can just pull it out at the end of the season and compost it, but I leave it lay and put down new whenever it seems to need it.

If you live in Slug Central - say, Portland, OR - there may be slugs coming to live in your garden, but if you've kept the cardboard back to the drip line and don't mulch all the way up to the plant stem, it shouldn't be too bad. I've only ever seen slugs in one place where I've used this method and it wasn't a big issue. There's always Slug-Go if it gets to be a problem.

If slugs are a problem you should probably remove the cardboard at the end of the season and compost it so they don't overwinter. I've not had a problem with anything overwintering myself, but the potential is probably there.

This post was edited by zensojourner on Tue, Sep 30, 14 at 2:42

Excellent post, thanks! Last year I put a new border in and used cardboard to kill the grass that was now becoming part of my garden bed, it worked well. Also I hate throwing anything out without reusing, so it's also a great way to recycle. I never thought about using it in the current beds.
I do have slug problems, but if you cover the cardboard with compost before the mulch, it's deep enough not to be a problem. I also need to consider PH in some of my beds as I grow blueberries. They like it at about 5.0. Again excellent idea I really didn't think about using it, and I could in some of the beds. other beds I have self seeding annuals, so I would not use it there. I don't mind fighting the weeds there. The annuals are used to attract beneficial insects. Most of my gardens are for edibles. I'm into edible landscapes and even the flower garden has strawberries as ground cover, so there too, I couldn't use the cardboard. But some beds new stuff goes in every year as I rotate crops. It certainly can be used there. Thanks for bringing that up. I may prep some of the beds this fall with cardboard in preparation for the next growing season. It's been a good year. Not all crops came in as I wanted, but you learn, and I got some excellent yields on beans, strawberries, raspberries, and the tomatoes were awesome this year too. The pepper plants did well too! My fruit trees grew well. Next year is going to exceptional!