Good drainage is essential for drought tolerant plants and so gritty topsoil has been used, mounded up into bunds over rubble filled subsoil.
For large scale production they are grown in long, mounded rows, and replanted every two to three years.
The bed may be contained within a border such as concrete bricks or two by four lumber or merely mounded soil.
A very thin, low ring will look skimpy when paired with a thick, tall pillar candle, while a thick, mounded ring can overwhelm a taper candle.