New Guinea Impatiens hybrid in the garden of Kathryn Hipkin in SydneyImpatiens hawkeri is native to Papua New Guinea and the Solomon Islands. They have been popular as a greenhouse plant since the 19th century, but they have been improved by much hybridisation in recent years. They have the same rich, jewel-like flower colours of the ordinary 'busy Lizzie' (Impatiens walleriana) and also bloom very well in part-shade. However, the flowers are larger and more showy, and the plants are more sun-tolerant than their cousins, which wilt dramatically if exposed to direct sunlight. Morning sun seems to be best for the New Guinea varieties; too much sun can apparently be detrimental - though some (such as the 'Sun Patiens' series) are marketed as being quite sun-hardy, as long as they are kept well watered. Too little sun can result in a leggy plant with fewer flowers. A morning sun position is ideal. They are not afflicted by the 'impatiens downy mildew' that has wiped out busy Lizzies all around the world.
New Guinea Impatiens hybrids look good in containersThe plants have a neat, mounded shape, to a height of 20 to 30 cm. They are perfect for containers - in a big pot, three plants will grow together to form an impressive mass. They are self-cleaning - so no dead-heading is required. If they are grown in a pot set on paving, wooden decking or tiles, it is advisable to sweep away fallen flowers regularly, as these can adhere annoyingly to the surface after a while. They can also be grown in the ground, but do need a rich, moisture-retentive soil. Regular watering is important to keep the plants looking healthy (especially in the early weeks after planting), and regular applications of a water-soluble fertiliser will be much appreciated. Some growers recommend using high-potash food, such as tomato fertiliser. Occasional trimming back during the growing season will promote a compact form. They flower for a long period, from late spring until the end of May - possibly even longer in warm microclimates.
New Guinea Impatiens hybridrange from bright hot colours of reds and oranges, to cooler hues of white, pinks, cerise and purples. Some of them have interesting foliage as well. They are look very at home grown with semitropical shade-loving plants with exotic foliage, such as Colocasia, Calathea, Iresine and coleus. They can look very effective grown in a large hanging basket, as long as it is kept well watered. Depending on how cold winter gets in your area, the plants may need some protection over winter to survive. They shouldn't be pruned until September, even if they look very ratty and gawky through winter. As with coleus plants (which sometimes don't get through winter in my garden), I take cuttings in autumn - these Impatiens don't self-seed. Propagation is as simple as putting a few stems into a vase of water on your kitchen windowsill, and watching them take root!