Eucalyptus risdonii

Eucalyptus risdonii is a species native to southern Tasmania, where it only grows in a very limited geographical area. It is a bush or sometimes a small tree that has the peculiarity of keeping its juvenile foliage for a very long time. The opposite, heart-shaped leaves have a superb silvery blue hue. This colouring is even more accentuated when clusters of small white flowers appear at the leaf axil. Growing on well-drained slopes, it is one of the most drought-resistant species, but not very hardy

Eucalyptus risdonii belongs to the vast botanical family of Myrtaceae, which has nearly 6000 species in the tropical and warm temperate regions of the globe. This Eucalyptus grows naturally in a small area of ​​southern Tasmania, near the locality of Risdon which gave it its name. It is found at low altitudes, on the dry slopes east of the Derwent River, in low and open forests.
It forms a bush of a few metres high, occasionally a tree of 7 to 8 m (23 to 26ft), whose trunk carries a light grey bark, which peels off here and there in strips, leaving a smooth, yellow to cream, ornamental surface. This species develops a lignotuber, a swelling rich in starch at the base of the partly underground trunk, which allows the regrowth of buds following a fire.
Another peculiarity of this species is it keeps its juvenile foliage for a very long time, sometimes always. This is what makes it a very ornamental species, as this juvenile foliage is extremely decorative. The sessile and opposite, heart-shaped leaves are fused at their base, with a size from 3 to 5 cm (1.2 to 2 in) long and wide. They are bluish, very glaucous, with silvery reflections. The foliage is very aromatic, which gives this plant its name of "silver peppermint". The branches are dense and bushy. The adult leaves, when they form, are significantly less attractive, with their somewhat dull green colour. Arranged in an alternate manner, they are elongated (10 cm (3.9 in) x 2 cm (0.8 in)) and crescent-shaped.
From November to January in Tasmania, which corresponds to our summer, white flowers appear from silver buds in groups of 9 to 15 at the base of the juvenile leaves. The crown stands out even more silvery than usual, reinforcing the ornamental aspect of the bush. The flowers are small, measuring 1 to 2 cm (0.4 to 0.8 in) in diameter and form small, capsule fruits, without ornamental interest.
This Eucalyptus develops in neutral to acidic soils, not appreciating limestone. It does not dislike drought, it is probably the Tasmanian species that tolerates it the best. Like most Eucalyptus, it thrives in sunny exposure. Although from the south of Tasmania, therefore in an area far from the Tropic of Capricorn, this species is not very hardy. It withstands brief frosts down to about -7°C (19.4 °F).

This silver Eucalyptus will form superb scenes, associated with other plants with ornamental foliage, like the purple Bailey's Mimosa (Acacia baileyana Purpurea). This bush with finely cut foliage develops purple young shoots which will form a sumptuous contrast with the silver foliage of the Eucalyptus. For an even more pronounced contrast, opt for the dark purple foliage of Pittosporum tenuifolium Purpureum, a small bush native to New Zealand. Banksia integrifolia, a tree-like Proteaceae with dark green evergreen foliage and large pale yellow flowers in tight spikes, will also be a good companion to create an exotic scene.