How to kill seeds in straw bales
This summer I mulched my garden with straw, for the first time. It is working great for water retention, but there were apparently lots of seeds left in the straw. The rows have been thick with grass germinated from the straw. It has added hours of work weeding the mulch! So my question: Is there a way to kill the seeds before using the straw as a mulch? I've seen online suggestions to solarize the bales. Some sites said to wet the bales before encasing them in plastic. But I haven't seen any reputable sources talking about it. I hoped someone at OSU Extension could provide guidance and instructions.
Douglas County Oregon
One option is to place a barrier of newspaper down before you lay out the straw. Also you can look for "weed free" straw at some garden centers. Also try to purchase straw from a field where the grain has been harvested before the baling of the straw. This is usually weed free. Some times you can find rice straw from California for sale and this is usually weed free.
Hope this helps.