Dictionary of botanic terminology
index of names

A "root succulent” is a plant that stores water in enlarged, specialized spongy portions of their roots; a plant with fleshy and juicy roots.

In general succulents are plants that store water in their plant tissue, they may be loosely grouped as:

• Stem succulents: (most of which are cacti) plants the have swollen, moisture-retaining stems.
  (e.g. Pachypodium namaquanum)
• Leaf succulents: Plants that have foliage but often lack a stem, whereas cacti and other stem succulents have a swollen stem but mostly lack leaves. (e.g. Echeveria laui or many vygies, i.e. members of the family Mesembryanthemaceae – commonly referred to as mesembs)
• Root succulents: Plants the have swollen, moisture-retaining roots. (e.g. Pterocactus tuberosus)
• Caudiciforms & pachicauls: Plants the have swollen, moisture-retaining trunks. . (e.g. Uncarina grandidieri, Adansonia digitata)
• Bulbous: Plants that have swollen, moisture-retaining bulbs. (e.g. Ornitogalum caudatum)