雲仙地獄の周辺では強酸性の噴気と高温の温泉が流れ、これらの厳しい環境に耐えられる植物が自生しています。

温泉のそばや噴気のすぐそばで見られる九州の温泉地特有の植物が雑草のように見えるツクシテンツキです。「つくし」とは九州の意味です。

温泉の高温、強酸性のそばでも生育する事ができます。
その他、地獄歩道周辺で目立つ植物では、４月下旬頃からピンク色のミヤマキリシマが咲き始め、ツツジの仲間のシロドウダンが５月中旬頃に、シャシャンボが７月中旬頃に白い花を咲かせます。

★ 英語バージョン
　As you enter the jigoku area and begin to smell the sulfurous gases coming from deep within the earth, you might be wondering how plants could possibly live here. Yet as you can see, there is a unique, thriving ecosystem all around you.
　Noxious gas, water temperatures of nearly 100-degree Celsius, and highly acidic soil—the plants of the jigoku are adapted to this challenging environment. The tallest plant capable of growing here is the akamatsu, or red pine. Below them are shrubs such as Hawk’s claw peppers (takanotsume) and several species of azaleas, such as the miyamikirishima azalea, which blooms with pink flowers in late April. Other plants include the twisting red trunks of the Oval-Leaved Lyonia (nejiki) and the fruit-bearing shashambo, a low shrub in the same family as blueberries.
　Plants can survive even right next to the bubbling water and gas vents. Here you can see bunches of maiden silver grass (susuki) and tsukushitentsuki, ordinary-looking grasses only found in hot-spring areas like this.