Since the rubble is already well draining (and presumably non-toxic) I would be inclined to build up with soil additions. I'd rather have a raised bed closer to working height!
They are already comfortable height for a dinky person like me. I don't think you could build them up, anyway. They are made of paving slabs on end tied with building ties, and are already a good two feet high, and pretty full, so increasing the soil depth is not really an option.
I think even short shallow things will struggle. They really are like 4x1 metre grow bags. Sure I could rig up some kind of watering affair, but it seems more sensible to go with the conditions. Things that I planted in spring did very poorly over the summer, but then pretty well into the Autumn, when crops of kale, squash, romanesco and broccoli appeared from nowhere. I really want things I can plant out in the autumn and harvest in late spring or early summer. Garlic and onions spring to mind and the kale has done ok. I think sprouts and leeks are out, but wind doesn't seem to have been a problem especially. The general area is fairly sheltered, so I'm looking for more ideas for winter veg, really.
||Going along the same lines as Gregotyn suggests, could you use them as plunge beds or stands for pots. Might be useful for things that required different soil, such as acid lovers like blueberries if your soil is alkaline.|
One of the reasons I suggested leeks and sprouts, but there are several cabbage varieties that are shallower rooting, and some of the cauliflowers, you just have to pick the winter maturing types. Winter brassicas need liming before you plant, as that is the best time to apply and not have the ground too high ph for the next spring crops after the brassicas. There is no question in my mind I would have to take some of the rubble out and increase the soil depth to about 9" over a period of time; the deeper the plants are in the ground the better they hold out in the wind, take up nutrients and water.
I agree that the higher the better for ease of gardening. I have boxes about 2 ft high for my plants when I am in the mood to grow "stuff". I like the sizes though, 4x1 metre grow bags sounds really good at about 2 ft high and you can sit to do the weeding-what weeds?
||I guess I'm not following why you're recommending shallower rooting varieties when the problem is already that the soil dries out too frequently. I would think deep rooting is ok, as the plant will be pulling nutrients from the top layers, and lower rubble layers will be explored (to the extent they can be - just what is our working definition of "rubble" here?) for greater stabilization and water|
||Alternatively, you could go for perennial crops with stupidly deep roots that will happily tunnel through the rubble?|
||What sort of things, NMG? Rubble is half bricks and the like.|