Most landscapes are impacted by a dozen or so invasive plant species. They all operate on their own calendar, and we scramble to keep up. A clean, complete extraction of the target plant generally eliminates re-sprout, but most important early on is to limit the size of the infestation by breaking the seed cycle. If you run out of time to pull individual plants, go ahead and cut, but come back through and check for late flowers. Plants like wild chervil and wild parsnip will flower at 4″ tall, so a follow-up is vital. Even if seeds are formed, you can go through and pull the plants or collect seed heads. Just be sure to dispose of that material in a designated place. And once the seeds are truly dry, once they easily shake free, it’s time to avoid that area or be extremely careful not to pick up seeds. Seeds get everywhere, that’s what they’re designed to do, and even dirt on a shovel should be considered “contaminated.”
But until that seed-drop starts, it is absolutely permissible to continue your control work. Keep pulling and cutting, just be sure to treat the vegetation with a new respect since it now carries viable seed. I’m a big fan of hotspots. No need to burn everything…. just condense these long roadside weed patches into single occasional hotspots or weed drying stations. Much easier to manage a couple of those rather than an entire roadside. You can always burn that spot or smother it later.
I tend to run tight on time in spring, so I’ll often try to get ahead of biennials like garlic mustard, wild chervil and wild parsnip with some pulling in the fall. Until the ground freezes, one can often pull the first-year plants. They’ll be the ones seeding next spring as second-year survivors, but not if they over-winter on the drying station. If time is available, some work in the fall can make spring a lot easier.