> Black locust and Japanese knotweed propagate via underground roots or runners. 

Japanese knotweed propagates primarily by seed, and as it flowers in late August to September, when few other plants are blooming, bees love it.

New York state says that the pollinated seeds are the primary mechanism for spread, as of course seeds can spread faster and further than runners:  "Japanese knotweed spreads primarily by seed (transported by wind, water, animals, humans, or as a soil contaminant), stem fragments, and by shoots sprouting from its system of rhizomes."

https://nyis.info/invasive_species/japanese-knotweed/

Black Locust can be easily propagated by root cuttings, but they are trees, so the seeds are how they have spread beyond a tiny local area.  Again, bees love them, and the quantities of nectar and pollen are impressive.

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