Yellowjackets do not re-use nests from year to year, so by the end of autumn (possibly earlier), all nest activity will cease and no live adults will remain so you can safely remove any nests at that point. If you cannot wait that long due to sting risk, then treatment with a wasp spray pesticide is probably the only practical approach. There is no pesticide-free and scientifically-proven effective alternative to nest removal that we are aware of. Blocking a nest entrance will only encourage the wasps to create a secondary entrance/exit.

Some pest control professionals use protective gear and a heavy-duty vacuum to remove worker wasps and dig out a nest for disposal (even then, they also probably make use of some wasp spray when needed), but we imagine such services are more costly and less easy to obtain, and we do not have a list of specialists to recommend since we don't collect information about services or recommend particular businesses. (We also don't have information about agencies or organizations collecting wasps for venom, sorry.)

The pyrethroid-class insecticide ingredient(s) typically used in wasp sprays have a bit of a residual since they need to last long enough to kill worker wasps not at the nest entrance at the time of application; they encounter the spray residues as they enter and leave a treated nest, so it's generally a key factor in their efficacy that they last for a few days at least. Pyrethroids are synthetic versions of pyrethrin. All pesticides eventually degrade into more inert substances over time, and how quickly depends on the specific ingredient along with environmental conditions, such as exposure to sunlight (like UV light), temperatures, moisture, and soil microbes. In this situation, any soil contaminated with overspray is not likely going to affect any nearby plants since they do not absorb this kind of pesticide in that manner.

Miri

You're welcome.