My local stores don't seem to carry much in the way of pre-emergents. Especially the organic ones. About the only one I've seen is Preen and for some reason I think this stuff would prevent all new growth and not just weed seeds. Though admittedly I've never even read the label on the stuff... The only stuff my local stores seem to carry are the chemical weed killers that are fairly turf specific. These are out for me as my 'turf' is some mix-matched blend of different grass types, so using a turf-specific weed killer would leave me with brown patches and areas. Maybe some day I'll splurge and get some St. Augustine to lay down over my lawn areas and homogenize my lawn, but for now, I have other things I would rather spend my money on. But I would love to hear other people's experiences with these pre-emergents, especially the organic ones. If they work, they might be worth ordering a bag online. Especially if they stop Southern Sandspur. I'm just worried about also ending up putting a halt to Mimosa seed germination and other types while trying to halt the weeds.

To get rid of clopyralid & related residues in hay, the material must be hot composted for a year, or it must be used as an amendment in an area where the area is regularly irrigated. The stuff won't degrade in dry storage, whether exposed to sunlight or not. It's useful to have facts at hand, including info about a simple assay any gardener can do. (In fact, it was already described in a previous response. Take a look at these sites/pdfs: - From NCSU: http://content.ces.ncsu.edu/herbicide-carryover  - From WSU: http://whatcom.wsu.edu/ag/aminopyralid/bioassay.html - From UNL: http://extensionpublications.unl.edu/assets/pdf/g1891.pdf - From Montana: http://www.pesticides.montana.edu/pat/Coordinators/non-target%20plant%20toxicity/Montana%20Herbicide%20Carryover%20Booklet%2011-2011%20LO-RES.pdf

Bare rooting 1000 golden barrels seems inconceivable to me. And oxalis is capable of withstanding long periods without water since they're corms. I was once given a small sack of corms, forgot about them in the sack in the garage for almost a year and most of them flushed out when planted. Plus, you'd need to completely remove and replace all the soil since the oxalis corms tend to hide out very well when they're small. The bite that would take out of your profit margin probably isn't reasonable. WBG also functions, though at lesser level, through soil contamination. The half life is pretty short in rich soil with lots of biological activity, probably much less so in a cactus type mix. My preferred herbicide is glyphosate. It is only effective when foliar fed and will not impact a plant through the roots. You can dump a gallon on the soil around a plant and nothing will happen to it. WBG functions by causing very quick growth that outruns the plant's ability, causing failure. Glyphosate works by shutting down the metabolic functions of the plant, so it starves. So, you may see a rapid growth spurt with WBG before it dies, leaving a lot more dead plant material in the pot, which may be more unsightly if you want to market them soon. I use a sheet of cardboard, a flexible plastic cutting board or an umbrella to shield the desired plant from overspray. But you can use anything handy. No need to leave the shield in place, you can just move it along with you. The amount that can transferred by touch has never been an issue for me. I always add a tsp of dish liquid (original Dawn) per gallon to function as a surfactant, add an extra ounce of concentrate than prescribed (particularly for tougher weeds like Bermuda, nut sedge, etc) and only apply during dawn or dusk and when wind is calm since glyphosate is only effective in liquid form and sun/ wind will quickly dry it. Plus, wind will blow the spray around, increasing threat to nearby desirables. Rewetting does not reactivate. I've used the generic glyphosate made by Eraser, which is a higher concentration (so, much cheaper per diluted gallon) but for some reason does not show results nearly as quickly. So I prefer good old roundup, results can be seen in about 3 days verses 2 weeks. Keep in mind that not all corms will be foliated, which means they won't be treated unless they're still attached to a foliated corm. So you may need to treat, then to water when your cacti are ready for watering in order to call out additional corms and treat again. Same with any seeds lying around. Sounds like a big job. Good luck.

Label says it just needs to be dry. I would not reapply any time soon.