The sunn hemp is doing well on Veg Hill East. We planted it on June 14, and after a little more than a month it’s as tall as 48 inches. The problem is that in other areas it’s as SHORT as nine inches. What gives?
All this was planted on the same day using the same method.These are in areas that get approximately the same sun and all irrigated with drip tape, so we can’t trace it to differences in sunlight or water.
I choose to view this as an opportunity to record the relative fertility of the soil, so yesterday I planted flags at 10 foot increments and took readings of the sunn hemp height on each row and every 10 feet.
As you can see in the spreadsheet, the lower values tend to cluster at the south end of Veg Hill. There’s a remote possibility that there truly are differences this dramatic in the native fertility of the soil, but I find that hard to accept. These areas are in the same geological formation within 100 feet of each other.
I don’t know the reason, but I have a theory. There were trees growing on the south end until very recently; we cut them down in the spring. I speculate that the trees are allelopathic and that the toxins they left are still in the soil and inhibiting growth even after the trees are gone. I have searched for some indication about how long the allelopathic effect will linger, but so far without success.
Here is the spreadsheet:
And here’s a quick video so you can see the difference for yourself. It runs 1:45.
I know for sure that water oaks are allelopathic so it’s quite possible that’s your problem. You might find more info if you do research on the specific trees that grew there.