Don’t think you can plant trees in containers? These birch trees are placed in large containers, and because the root ball is kept from growing outward, the whole tree remains smaller and more manageable.
Eryngium variifolium or sea holly suits a seaside spot. Sea holly is a stunning architectural plant with silvery bracts and egg-shaped heads with delicate blue flowers. It is hardy and will grow happily in full sun and poor soil.
Mexican tree ocotillos + agave: Here, fanlike Mexican tree ocotillos (Fouquieria macdougalii) serve as a backdrop for equally spaced agaves (Agave ‘Blue Glow’) and low chartreuse Sedum rupestre ‘Angelina’.