It's likely that you're watering too often. The water IS free to migrate into the soil beneath the containers - yes? Oh wait - I just reread your post. If you have mesh over the holes & there is an air space under the bottom, that could make a significant difference. If you have a soil to soil bridge in your other containers, they will behave like raised beds, as far as water movement is concerned; but if the whisky barrels don't have that bridge and aren't wicked, they'll behave like conventional containers. Al

I have rhododendrons that grow near black walnuts. The black walnuts killed some before I discovered the problem and killed the walnuts. I just girdled the walnut trees. It took them three years to die and after over 15 years they are just now beginning to fall over. The rhododendrons in the area are coming back strong and healthy. I think that if you do as you say and remove the leaves, nuts, etc., they will be OK. I can't imagine the dripping rain water is that bad. The live roots are what did mine in. I think it is worth a try.

Farsighted, Your plant here looks pretty healthy to me. I think you were right in saying that the dwarf variety grows slowly. I have a non dwarf Tahitian planted in the ground for a few years already. The first couple of years, it didn't grow too much and it didn't bear fruit. This year being its third year planted, it is showing a little more growth and is fruiting now. Last year, it also flowered, but the blooms all dropped except for a couple which carried themselves to fruition. So, with my own limited experience, I think this variety is not a fast grower. That said, you have nothing to worry too much about your plant. It's a healthy looking dwarf, so it looks like you're doing all the right things to feed and water it. The only thing though about citrus fruit trees is that they don't like wet feet and over watering or mulching especially around their trunk. Lots of sun is good for them. I'll post picture of my plant later. Hope your dwarf will take off when your hot weather comes. Are you having Summer now in NZ?

I grew borage last year and had no problems with it. I have heard that it will reseed, but nothing about it taking over or acting "invasive". I reseeded some as I had a couple of plants come up late in the summer. We'll see if they come back this spring. I hope so. Borage and Basil seemed to do well next to my tomato plants. Cilantro was a bit invasive. I also didn't have any issues with onions. I would not recommend marigolds as they attracted spider mites. The only thing that I found that worked was to spray them down with high-pressure water from the hose at least twice a week.