As well as clustering smaller pots, you might have the space such as a roof terrace or side return that merits a large trough or planter where you can indulge in large trees and shrubs.
When planting larger planters, approach it as you would a raised or island bed, where your starting point might be a specimen shrub or tree for height in the centre. For an exotic spiky feel, opt for palms such as chamaerops or larger structural plants like trachycarpus, yucca or phormium. Multi-stem or half-standard trees such as olive, bay, arbutus (strawberry tree), phillyrea or dwarf pine would also provide good evergreen structure, as would the large-flowering shrub oleander.
You can then build up more mound-like structure will smaller ball-shaped evergreen shrubs such as Pittosporum tobira ‘Nanum’, dwarf pine, santolina, small cistus, lavender and hebe. Silvery ballota or Convolvulus cneorum would also look great tumbling over the front of the trough.
Once you have some structure in place, start adding herbaceous plants for colour. Include sun lovers such as agapanthus, sedum, salvia varieties, achillea, gaura, verbena, fennel and centranthus for height. Lower-growing dianthus, pelargonium, osteospermum, Erigeron karvinskianus, Stachys byzantina and Geranium ‘Rozanne’ will spill over the edge. You could also use trailing rosemary prostratus and stunning blue-flowered Convolvulus sabatius to trail over the edge.
Grasses are a great addition for height, texture and movement. Try varieties such as Festuca glauca, Stipa tenuissima and taller sturdy grasses such as miscanthus. Even deciduous grasses provide excellent winter structure lasting through the season until getting cut down in spring. Then come autumn, pop in some bulbs such as allium, tulips, daffodils, crocus and liriope for some spring colour.