Q Why is my rhubarb going into decline?
Awela Jones, by email
A BOB SAYS Weak growth on rhubarb could be caused by bacterial crown rot, which is a brownish wet decay. However, you’ve not mentioned such signs. A viral infection causing lack of vigour is possible but unlikely, as is honey fungus (Armillaria), unless that’s present elsewhere in your garden. There could be herbicide residue in the manure you use or in the planting site, which could cause weak growth, but you’d likely see distorted foliage as well.
Your growing method using manure and plenty of water sounds exemplary, so I assume it’s neither planted in the shade, nor in the root zone of large trees or shrubs. You say you moved the rhubarb – I wonder whether you
kept the clump whole or divided it into smaller chunks taken from the outside, each with a fat bud? An old, congested rhubarb clump can stall and seldom recovers from a move as well as good ‘offsets’. I’d dig it up, divide it and re-try in a new spot, or just buy new plants.