I followed Toby Hemenway's instructions in his book Gaia's Garden for sheet mulching. I live in a drought area with about 11 inches of rain per year and I wanted to create beds that needed less water, I didn't have enoughwood for a hugelkultur bed. I used the same materials as Tody describes but instead of the 8-12 inches of hay, I used straw, and only about 2-3 inches and on the top I also used straw. I used straw instead of hay because I thought straw was dead and it wouldn't germinate seeds. It's been about a week and a half and now straw is growing in between my plants.
On another bed, I followed his instructions exactly and used 8 inches of hay in the middle layer and then straw on top. I hope this one turns out better. But, I'm afraid the straw or hay is going to germinate too!
On closer inspection of the straw, I found seeds in there. My little plants are very happy, but now what do I do with all the grass growing in between? I was thinking of putting cardboard on top and cutting holes for the plants and then putting wood mulch. (because now I am scared of straw/hay)
Good straw doesn't have seeds in it. You didn't do anything wrong. You just got straw that had seeds in it. Your cardboard and wood chips idea will work fine. Anywhere you have straw grass coming up, just pile something over it that doesn't have seeds.
"People may doubt what you say, but they will believe what you do."
I wouldn't worry too much about some grass growing. Other plants are going to find their way into any good system. And green organic matter from unplanned appearances is just as good as any other.
Your idea of covering the growth with cardboard and wood should work. I might let the seedy straw sit uncovered for a few more days to allow seeds to sprout and start catching sunlight, then cover them. But definitely don't give up! A permaculture system doesn't match the neat and clean commonplace ideal. It's a fuzzy system, just like nature. Free / really cheap hay or straw can be a way to bring organic matter in large quantities to your garden.
Jazzy Paulson wrote:What is the best way to find straw that doesn't have seeds in it?
I think the best thing to do would actually be to grow your own cover crops, which is very doable once you have your garden going. Then you control when exactly you cut the crops. Otherwise you are always at best trusting the source.
Things like buckwheat, red clover, vetch, etc. can be grown until they blossom then cut to prevent seed development. You could then move the cut material to your main bed. If you have a good garden store near you, clover seed is easy to get. Otherwise buckwheat groats are often available at the food coop and will grow well.
The best of all might be to mulch with compost and/or leaves (assuming you have some) when you plant seeds or transplants, then plant white clover (which is lower-growing than red) in-between your preferred plants. That will do a lot to keep out the less-desired plants. And if something unexpected pops up and bugs you, well, you are usually safe to pull it, dry it (to prevent sprouting), and put it on your garden.