My first encounter with this tree species was actually in aromatherapy seven years ago. Both Niauli oil and Cajuput oil, extracted from another variations of the Melaleuca plant (Niauli oil is from Melaleuca viridflora and Cajuput oil is from Melaleuca cajuputi), are good antiseptics and stimulants. Niauli is a very good healing and relief aid for respiratory infections, and one of my favourite home-use vapouriser oil during influenza season*. Cajuput oil is great with digestive and skin problems*.
(*Use Niauli and Cajuput essential oils with caution. Check out proper aromatherapy literature or consult aromatherapists for safe and correct use.)
Though having a somehow similar Chinese name, Paper Bark tree is of another Melaleuca category – Melaleuca quinquenervia. It is distinctive with its greyish white and beige multi-layered peeling papery bark.
Native to Australia, New Caledonia, etc., Paper Bark Tree was introduced into Hong Kong as in the last century. It is now a common street and countryside tree. Melaleuca quinquenervia grows from 8–20 m (25–60 ft) high with a spread of 5–10 m (15–30 ft). Its flowers, in cream or white colour, look like bottle-brush!
Despite a peeling bark, Paper Bark Tree is highly adaptable to unfavourable growing environment, drought and flooding, nutrient-poor soil, and tolerant of fire. The inner layers of its trunk are nonflammable, hence when a hill fire occurs, paper bark tree can prevent the fire from spreading.
I love to visit the Paper Bark Tree path and vast area of Paper Bark Tree foliage next to Shing Mun Reservoir – they are familiar local filming sites!
In the U.S., Melaleuca quinquenervia has been classified as an exotic invasive species that is capable of displacing native species, changing hydrology and soil content, and reducing native habitat value.
與白千層緣起於香薰治療：白千層與綠花白千層萃取自白千層屬Melaleuca viridflora和 Melaleuca cajuputi的枝葉，兩者都是有效的「消毒」類精油，穿透力強。綠花白千層是我最喜愛的流感高峰期家用薰香精油之一，是舒緩呼吸道感染和保健的佳品*；白千層精油即白樹油，是製造白花油、萬金油的成分之一，對皮膚和消化系統亦有療效*。
(*須小心使用白千層與綠花白千層精油，不可口服，應諮詢芳香治療師或參閱相關典籍查詢正確的應用方法及安全劑量)
後來才知城門水塘的地標樹林，即舊時武俠片拍攝聖地、那主角比武練劍、密會郊遊的樹林，種的就是白千層樹。上世紀由澳洲引入的白千層，在城門水塘成林後，竟是「製造」香港人的古裝片集體回憶的其中一員！
香港的白千層樹屬另一Melaleuca 屬 – Melaleuca quinquenervia，常見於路邊和郊外。灰白、粉色海綿質樹皮隨樹齡增長不斷更新、層層剝離，觸感鬆軟，很易認出。白千層可長致20米高，開花時穗狀白花看起來像一個個洗瓶刷，很有趣。
白千層適應力強，耐旱、耐水濕，抗風耐鹽，雖有「紙狀樹皮」，但樹幹內層不易燃燒，一旦發生山火，白千層可減低火勢蔓延，幫助抵抗林火。
在美國，白千層被列為外來入侵物種，認為它的生長習性會取替本地物種、改變水土、和減低本地自然生境的生態價值。但據說，白千層在香港並未出現此等野化現象。
Chinese Banyan 