Portulaca grandiflora – Moss Rose is a low growing (12″ spread) half hardy annual with succulent foliage – ideal for planting in those shallow containers that tend to dry out. Colours range from white, orange, yellow, pink, red or purple, and they come in single (hard to find now) or double forms, with contrasting yellow stamens. The flowers can close-up on dull days.
Celosia argentea var. plumosa – Cockscomb Celosia is quite an exotic looking half hardy annual with feathery plumes of yellow, orange, pink, red and purple that make good cut flowers. Do not plant these outside until all risk of frost has passed (they do not thrive in cool weather) and remember that these summer flowers are only drought resistant once established. Grows 6-24″ high.
Gazania x hybrida – These are large-flowered half hardy annuals with green or silver foliage and often bicolour blooms of white, yellow, orange, red, pink or purple – with a dark contrasting central ray. Gazanias are fairly compact summer flowers (averages 8″ tall) that make a great mass-planting specimen on the edge of dry borders. The showy flowers close up at night and on dull days.
Zinnia x hybrida – For sheer range of colour, the single, semi-double or double blooms of this half hardy annual are hard to beat – so expect every hue, including green. Zinnias hate cool, wet springs so if this is a problem in your area, delay planting until the warm weather begins. Heights are rather variable, ranging from 6″ to 2.5′ on average.
Tagetes tenuifolia (syn. Tagetes signata) – This poor cousin of the Marigold is a half hardy annual with tiny yellow, orange or red blooms and fine-textured foliage with a pungent scent. A versatile summer flower which is often found in containers, hanging baskets or used in mass displays, much in part because the flowers often smother the leaves below.