Posted: 08/01/2015 at 16:10
Gemma - I think your idea of a mobile frame would work quite well & the compost etc that you leave behind each year would help improve the soil underneath.
The only thing I would question with a single mobile frame is when you would actually move it - the garlic would be in from autumn to early summer by which time it would be planted up with summer crops. If you have room for 2 or more frames that might work better.
Other advantages of raised beds is that they warm up much quicker in spring than cold clay and the controlled contents mean direct sowing is usually more productive. If you can afford it, the company Harrod Horticultural Products do some smaller frames in various shapes & sizes which might be more moveable or easier to take apart each year. Their products are nice and sturdy but they are an easy rather than a cheap option.
Otherwise I have had success just using old bricks (loose laid) to essentially contain the contents of a few bags of MP compost. This just gives a few inches of friable compostey soil over pre-dug soil. The bricks can be moved to a new site as needed and can be used to make containers of different sizes.