From my experience, Westringias are not that delicate. When you pulled up the dead plants, Johannes, did the roots show telltale signs of twisting round each other? Olivier Fillipi described this graphically in his lecture to the 2007 MGS Symposium when he produced a dead tree sapling pulled up from an Athens pavement! Since then whenver I remove a dead plant (quite often) I check for twirling of the roots and I find it I'm afraid, though only with bought in plants I should add. If the roots have started to circle in the pot then after planting out there is a danger that rather than venturing out into the surrounding soil to look for food and water, the roots will continue to twist and not be able to support the growing plant.
