Before adding plants, neutralize the portland cement by rinsing the finished trough with 1/2 cup white vinegar in 1/2 gallon water. Allow container to dry.
Place a piece of wire mesh over drain holes to allow water to drain without losing soil and to prevent slugs from creeping into the trough.
Make a planting mix that holds moisture and drains well by combining equal parts humus, peat or leaf compost, and sand.
Plant the trough with an array of sun-loving alpines or slow-growing plants that have similar needs and are adapted to your climate. Cover the soil with 1/4 inch of pea gravel to help hold in moisture and give the garden a finished look.
Set the trough on top of a concrete block, bricks, or hypertufa blocks in a protected place where it receives morning or late-day sun. Water the trough garden regularly (every other day in hot weather) throughout the growing season. Do not allow the garden to dry out. Water it with diluted fertilizer once a month. Over time, troughs develop mossy, weathered-looking character.
Select from a huge array of compact, low-growing, and dwarf plants including varieties of: Alyssum, Armeria, Campanula, Dianthus, Gentian, mosses, Primula, Saxifraga, Sedum, Silene, thyme, Viola.