Need to see a picture. A "moat"? Not sure what that means.

a ditch/dip around the plant so the water can be added. a moat was a water defence around castles etc in Britain and Europe, especially medieval times.

I know what a moat is thank you lol. I want to see how it's used in this instance.

you dig a small moat around the plant to add lots of water to the surrounding ground with out putting it directly at the base oft the roots/stem.

Lol you are funny

What is your soil like Bhall? Putting a moat round the rhododendron is not going t help if the soil is poor...

Rhododendrons love their water, but they don't want to be submerged.

Basically the soil is acidic but not too heavy.On the left I have well established -azalia-magnolia stellata-acer-enkianthus- rhodo-spindle tree- to the giant birch & spring woodland. On the right I have wild geraniums-amelanchier-spring garden-the dead rhodo-wip- sarah bernhart-mini apple tree-tree peony -small conifer-hydrangea- knackered plumb tree- small conifer-massive bed of a perenial that escapes me fot the minute -escalonia - giant pitosporum. But there are pockets of more sandy soil. I took out a bed of montbretia several years ago & planted anuals & perenials but west facing by a fence is tough. The sarah bernhart peony was disturbed but getting better. The tree peony is thriving & the hydranger is newish bur ok. Things self seed & there are other plants & bulbs not mentioned but there is room for soil improvement on the right but the fence is 5 ft so plants are fighting for morning light.

Oh from the kitchen window the first plants are the wild geraniums -pond lillies-varigated weigela covering the old dark base of the amelanchier. The weigela has less flowers now with the fence

Without a photo, I can only guess what the problem can be. Something could be attacking the roots, but I can't be certain. If it's dead, now is a good time to replace it. I don't think the 'moat' is a good idea. These naturally grown on alpine mountainsides. They need moisture, but also need excellent drainage. Too much water will cause root-rot. Add a couple inches of pine mulch - shredded bark or pine needles - it has an acidic base.

I'm glad I amuse you Bathgate but you did ask.

with all the plants around it, it may just not have had enough water to keep it going.

but photos would be a great help.

No SBG you misunderstood my point. I wasn't asking for a definition. I have a dictionary.

its because you said "I want to see how it's used in this instance." that I described it. glad you have a dictionary they are going into decline :p

but as moats are medieval not everyone knows what they are.

I was asking for a photograph so I can see what is described as a 'moat' in this specific instance with this specific rhododendron. Is it submerged or not? Does the 'moat' cut through the roots? This is what I was getting at. I'm sure there aren't alligators swimming around like Monty Python. I was asking the writer, not you, lol!