Hello Colin! Congratulations on the new land! Ah, the Japanese knotweed. It is a powerful plant, but it can be managed. How large is the area where the knotweed is growing? How large is the property overall?
What do you think the knotweed and black locust might be telling you about the soil in that area?
On our land, we found the greatest density of knotweed in the most compacted, clay heavy soil. It even broke a rock it wanted to grow through!
Since it sounds like the knotweed is on the edges, I would just mow or machete it frequently. It will take time, but if it never gets the chance to photosynthesize, it will weaken and die eventually.
Its
roots can extend quite a distance from where you see shoots. I would be
extremely cautious about transplanting other plants in the vicinity to elsewhere, lest you inadvertently spread knotweed to other properties. Maybe make a habit of either growing in containers or removing all soil from the roots of plants grown in the ground and checking for knotweed roots before sending them elsewhere. I would highly suggest familiarizing yourself with what the roots look like so you can be sure you aren't spreading them. They can regrow from very small
root fragments.
For perspective, the land where I live has quite the Japanese knotweed presence. Probably about a 40 foot diameter circle of it. We are unwilling to use poison and it doesn't sound like it works that much better anyway. We have tried several tactics over the past two years we've been managing it. It is still present, but we have learned a lot and it does seem to be weakening considerably. We chose to site our garden where it grows, partially because it would encourage us to stay on the knotweed removal. At first, we tried eating it. Tasty, but couldn't eat much before the high oxalic acid content became apparent and unpleasant. We picked tons of shoots in the early season and sold them to a fancy restaurant. We cut down their stalks as often as possible, but definitely before they could flower. We eventually decided to dig out the largest clusters of them and then burned them along with all the honeysuckle we cut over the spots we dug them from. We spent a lot of time tracing the smaller roots and digging them too. Since all that, we have just been pulling the shoots as soon as we see them to stop them from photosynthesizing. If I had it to do over again, I wouldn't have wasted my time with tracing down smaller roots. I do think digging out the largest clusters of roots was worth it. Though I really wish I'd either dried them or made them into a tincture, as Japanese knotweed root has many
medicinal properties. Honestly, I think that continual cutting is the best strategy. Surprisingly, growing pumpkins over it was quite helpful in setting it back too. They out competed it for resources
enough that it rarely got above the pumpkin leaves. It seems too that the more we let other "weeds" grow that break up compaction, the less successful the knotweed becomes.