The time when the sun never set on the British Empire may have passed, but in her day Great Britain ruled many of the world's tropical regions. Hundreds of species of plants from those regions made their way to the United Kingdom during those years. They graced the conservatories and greenhouses of many a nobleman's ancestral UK home, and took up residence in Britain's great botanical gardens, where they remain to delight the 21st-century public. Some of them have adapted to life in home landscapes.
Sydney Golden Wattle
Sydney golden wattle (Acacia longifolia) is a tropical shrub or tree native to eastern Australia and introduced to the United Kingdom in 1792. In Australia and the United States, it's effective for screening road dust and oncoming headlights, states the BBC. While Sydney golden wattle can tolerate mild frosts, it's often grown as a greenhouse plant or container in the United Kingdom. Reaching as high as 23 feet, it's heavily branched, with grayish-green leathery leaf stalks (petioles) up to 6 inches long. In the spring, they bear heavy spikes of bright yellow flowers. Plant the shrubs in full sun and well-drained, acidic soil.
Black sassafras (Antherosperma maschatum) is a tropical tree native to Tasmania and Australia's temperate rain forests in New South Wales and Victoria. An evergreen hardy to winter temperatures of 20 degrees F and higher, black sassafras is an effective woodland garden plant in milder areas of the United Kingdom. Elsewhere it does well as a greenhouse plant, according to the Plants for a Future website.
A tall, narrow tree, black sassafras can reach nearly 100 feet high with a 33-foot spread. Every part of the tree is fragrant, with its nuts emitting a nutmeg-like scent. Male and female trees are necessary for pollination and nut production. Their fragrant, yellow flowers bloom in the spring. Black sassafras prefers a sunny to partly shady location with organically rich, pH-neutral or acid soil.
Another tropical shrub from the Australian states of New South Wales and Victoria, crimson bottlebrush (Callistemon citrinus) grows wild along swamps and streams. Like black sassafras, it's hardy to winter temperatures of 20 degrees F and higher. An evergreen, it grows up to 15 feet high by 8 feet wide. In the United Kingdom, cautions the Plants for a Future website, crimson bottlebrush is almost exclusively a greenhouse plant. It may tolerate winters in southern parts of the country with protection.
Varieties with small leaves, including the 'Splendens' cultivar, have the best chance of wintering outdoors. 'Splendens' blooms all year. Other varieties flower in the spring and summer, with filamented spikes of bright red blooms resembling bottlebrushes. The shrub's crushed leaves emit a pleasant lemon scent. Plant crimson bottlebrush in full sun and acid soil. It tolerates both wet and dry conditions.