We had one Edgeworthia that suffered summer decline similar to yours. It was planted in a heavily flooded location - not even standing water, only strong currents flowing in a channel on a hill after rains. It was growing fine for extended periods of time and then occasionally suffered wilting-like symptoms that occurred after heavy rains and set it back significantly leading to net decline. It was rescued by being extracted and kept in a pot for one year and replanted elsewhere. As a precaution we planted other Edgeworthias in slightly raised mounds, which is also useful for planting in areas with lots of roots competition, like under established trees.
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Container help
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