How to get rid of portulaca.
I live on a farm in Saskatchewan, Canada.
For the last 8 years I have been fighting with portulaca, I have tried everything, from hand weeding to the use of pesticides, the problem seemed to be under control this spring, only a few portulaca plants appeared in a few areas, we had an unusual dry spring. However, as soon as it started raining, the pesky weed has come up everywhere, it covers the areas affected like a carpet, and the areas affected is not limited to the vegetable garden, but to open areas around the house that have been worked up, these areas were worked up years ago before I knew what I was dealing with. Hand weeding would be impossible since the open areas affected are over 2 acres. Any help you would offer with be greatly appreciated.
Portulaca oleracea, also known as common purslane or portulaca, is a summer annual. It is one of those curious plants that is classed as a weed, an ornamental plant and, an edible. A satisfying option would be to find the niche market that likes eating purslane and sell them your 'crop'. More likely you will have to battle portulaca as a weed. A variety of U.S. Cooperative Extension resources note that portulaca is a prolific seed producer which is unfortunate since you likely have ample seeds in your soil for years to come. Portulaca readily germinates on tilled or disturbed land as you mention, so avoid soil disturbance. Seed germination is reduced when seed is buried 1/2 inch or deeper. Therefore the first recommendation is to apply at least 1 inch (2.25 cm.) organic mulch over the infested area to reduce portulaca seed germination.
Pre-emergent herbicides (applied early in the season before seeds germinate or perennials resume growing) are not as effective in northern climates against portulaca since portulaca germinates with high soil temperatures which occur late in northern areas after the herbicide loses effectiveness. Two post-emergence, non selective herbicides recommended in some southern U.S. States include Roundup (glyposphate), and Finale (glufosinate ammonium). In both instances Roundup and Finale are the trade names and glyposphate and glufosinate ammonium are the common names of the active ingredient which affects the weed. Of the two Roundup may be more readily available. If you use either product remember you are handling a hazardous chemical. Always wear appropriate personal protection equipment (PPE): chemical resistant gloves with no cuffs or liners, long sleeve shirt and long legged pants of a tightly woven fabric,safety goggles or eyeglasses. Read and follow the product label directions attached to the herbicide container. Since both of the herbicides listed are non-selective they most likely will injure or kill any plant sprayed with the mix. Use all the mixed herbicide at the time mixed. Allow at least 8 hours drying time after application before rain or irrigation. Do not apply when wind speeds exceed that listed on the label. Be especially cautious not to get any of the herbicide in your eyes. You will likely have to apply the mulch and the herbicide every year to control portulaca. Hope this helps.