Agonis is a genus of flowering shrubs and trees native to western Australia, with one species, A. flexuosa, being popular for domestic cultivation. Nurseries and garden supply stores sometimes carry seedlings or can order them by request for customers and there are a number of specialty cultivars such as the hybrid known as 'After Dark' that have some interesting physical characteristics. In the case of A. flexuosa 'After Dark,' the plant has rich reddish to purple foliage.
Common names like peppermint tree, Swan River peppermint, and Western Australian peppermint all reference the distinctive odor the leaves of Agonis species give off when crushed. The foliage in wild species is dull to dark green and the plants produce arrays of small white flowers. The bark is typically fibrous in nature, and the size of a mature Agonis plant can vary, depending on the species. Only A. flexuosa reaches full tree height.
These plants have a trailing growth habit and can become very leggy if they are not pruned and trained. They are also frost tender. Although they can survive a single night of low temperatures, even hovering around freezing, a hard frost will kill or seriously injure them. Prolonged cold periods can also cause damage. People living in marginal climates can try covering Agonis species on cold nights to limit the possibility of frost damage, or may want to grow indoors or in a greenhouse, where it is easier to control the temperature.
Members of this genus prefer soil with a neutral pH balance. The soil should be well drained and peaty, sandy, or loamy. Sun to partial shade is preferred. People in cooler climates should select sunny, sheltered areas for planting to limit damage. When transplanting, it is very important to be careful around the trunk and roots, as the plants are fragile and subject to transplant shock. If jarred or handled roughly, they may not thrive after transplant.
Peppermint trees can be used as specimen plantings in a garden and pair well with other Australian natives and drought tolerant plants. They can also be grown in clusters or established in lines for more visual interest. Specialty cultivars can add extra color to a garden. Pruning will help the trees keep their shape and can be used to direct and control growth. It is advisable to take care around long, trailing branches, as Agonis can be fragile and branches may snap if they are stressed.