・シロドウダン（花５月中～６月初旬）
ツツジ科の落葉低木で、雲仙では全域に分布しています。特に地獄歩道に多く見られ、昭和３年に国の天然記念物に指定されています。ミヤマキリシマの花が終わる５月中旬頃からスズランの花のようなクリーム色の小さな花を房状に咲かせます。
雲仙では、ほとんどがシロドウダンですが、稀に薄いピンク色の花が一部に見られます。また、秋になると、その葉は赤く紅葉します。
・ネジキ（花５月下～６月初旬）
高さ４ｍ程のツツジの仲間です。６月頃に長さ１ｃｍ程の釣鐘状のスズランと同じような、白い花を一列に並んで下向きに多くつけます。ねじれた幹が特徴で、冬の若枝が赤いため塗り箸の木とも呼ばれています。
アセビ同様に有毒植物であり、本来は庭に使われるような木ではないですが、幹が持つ野趣や渋みのある紅葉が好まれ、雑木の庭を中心に使われることがあります。
　特に葉の毒性（アンドロメドトキシン、リオニアトキシン）が強く、人間も食せば、嘔吐や痙攣を引き起こします。
英語バージョン
　White flower (flower mid-May to early June)
It is a deciduous shrub of the Ericaceae family and is distributed throughout Unzen. They are especially common on the Jigoku Trail, and were designated as a national natural monument in 1928. From around mid-May when Miyama Kirishima flowers end, small cream-colored flowers like lily of the valley bloom in clusters.
In Unzen, most of them are shirodoudan, but in rare cases, pale pink flowers can be seen in some areas. Also, in autumn, the leaves turn red.
　Nejiki (flower late May to early June)
It is a member of the azalea that is about 4m high. Around June, many bell-shaped lily-of-the-valley-like flowers, about 1 cm long, are lined up in a row and put downward. It is characterized by its twisted trunk, and is also called the lacquered chopstick tree because its young branches are red in winter.
It is a poisonous plant like Japanese juniper and is not originally used in gardens, but it is often used mainly in gardens with miscellaneous trees because its trunk has a rustic feel and its astringent autumn leaves are preferred.
The leaves are particularly toxic (andromedotoxin, lyoniatoxin) and can cause vomiting and convulsions if eaten by humans.