Hello. I am new here. I am interested in starting a raised bed vegetable garden. I have a question that I've tried to google, but it doesn't come up with an article that addresses the question, though I imagine the topic comes up regularly: My only option for the raised bed may be on a piece of land in which the grass was treated with chemicals, such as herbicides. Do the chemicals typically dissipate over a few months if not applied again? Would it typically be okay to use the soil after a few months? If not, would it be okay to bring in soil to put on top of it? (Or would it leach up through the new soil into the roots?)... Might it make sense to put some scrap wood blocks (untreated, of course!) or other filler in between? I imagine a lot depends on the specific chemical (herbicide, or whatnot) used.... Regardless of chemical use on grass, I would have the soil tested. I'd love to be 100% organic, but even if there are trace chemicals the veggies may be more healthy than the veggies at the local supermarkets, right? If anyone knows of an article or video online that addresses this issue, it would be much appreciated! I will give extra information below, incase it helps answer the question. EXTRA INFO: My wife and I live in Grover Beach / Arroyo Grande, California (Central Coast). 9b or 10a, I believe. Very mild summer + winter, near ocean. Often fog about half the day... We may move up to Morgan Hill, CA (near San Jose), which has more sun/heat in summer (lots of upper 80s/90s). Average low in January: low 40s in either location. I am most interested in growing (in order): beets, broccoli, carrots, green-leaf salad veggies, maybe cherry tomatoes. I plan on starting with one or two 4x10 foot raised beds, cedar walls, soaker hose. Probably metal mesh underneath bed and something over top to discourage ground burrowers and other animals.... 12 or 18 inches deep.... Starting worm bin now, so I have some castings to put in when we have the land. Thank you to anyone who can provide advice! -TravisCA
So any broadleaf herbicides would at least stunt your garden and you would know as the roots go down to the soil. It is normally no issue. The most common chemistry does not last the year in meaningful quantity. Some like quinclorac will, but that type stuff is usually aimed at specific weeds. Raised beds with floors are better for stopping soil borne insects and fungi though so it is a worthy effort.
I think people spray every month or 2? probably the chemicals are all gone by then. so if it's been a few months since it was sprayed, it should be just fine... If you're going to put your raised bed directly on the grass you'll probably want to put down some weed blocker fabric first, unless the raised bed is like a foot high or higher. metal mesh underneath bed sounds like overkill to me, just make sure your fencing around it is adequate and sunk into the ground a few inches, so they can't just dig a little and squeeze under the fence. cedar is expansive, untreated lumber will hold up just fine for years. turns out organic or not makes no difference health-wise, what makes a difference is actually eating veggies... most people eat far too much meat, substituting meat with veg makes a huge difference, now weather the veg was grown organic or not really makes no difference at all. the health benefits of homegrown veg, comes from having to go out there and do some weeding / manual labor, getting some sun, and having some fun. I wouldn't worry about using the non-organic products when needed.
I would start with a waterpan. Fold some corners on a sheet of pvc coated sign metal maybe. There is cheaper though I am sure. PVC shower pan liner would work. Same idea as you see on potted plants. Soil IS the jungle. And just like a pot, drainage is the next layer. Then soil etc. That way the water will keep you from working too hard once the roots find the water. You need a dipstick tube probably. It can be used to water tomatoes and keep them dry at the same time for fungus fighting reasons.
Don`t overthink it or you will spend more time worrying than planting and growing ! Most all the chemicals available to the public are extremely diluted and rarely even do the job they are purchased for ! They have a short life after use ! If you are concerned just build the raised bed and line the bottom with cardboard or several layers of black and white newsprint ! Then add the soil ! The cardboard and newspaper will provide a home and feed any worms you may have and will eventually rot and blend with the soil ! Worms will eventually eat through the paper and help your soil !