Raunkiær plant life-form

These plants, normally woody perennials, grow stems into the air, with their resting buds being more than 50 cm above the soil surface,[10] e.g. trees and shrubs, and also epiphytes, which Raunkiær later separated as a distinct class (see below).

Raunkiær further divided the phanerophytes according to height as

• Megaphanerophytes,
• Mesophanerophytes,
• Microphanerophytes, and
• Nanophanerophytes.

Further division was premised on the characters of duration of foliage, i. e. evergreen or deciduous, and presence of covering bracts on buds, for 8 classes. 3 further divisions were made to increase the total of classes to 12:

• Phanerophytic stem succulents,
• Phanerophytic epiphytes, and
• Phanerophytic herbs.

Epiphytes were originally included in the phanerophytes (see above) but then separated because they do not grow in soil, so the soil location is irrelevant in classifying them. They form characteristic communities of moist climatic conditions.[11]

These plants have buds on persistent shoots near the soil surface; woody plants with perennating buds borne close to the soil surface, a maximum of 25 cm above the soil surface, e.g., bilberry and periwinkle.

Hemicryptophytes

These plants have buds at or near the soil surface, e.g. common daisy and dandelion, and are divided into:

• Protohemicryptophytes: only cauline foliage;
• Partial rosette plants: both cauline and basal rosette foliage; and
• Rosette plants: only basal rosette foliage.

A cryptophyte geophyte

These plants have subterranean or under water resting buds, and are divided into:

• Geophytes: rest in dry soil as a rhizome, bulb, corm, et cetera, e.g. crocus and tulip, and are subdivided into:
  • Rhizome geophytes,
  • Stem-tuber geophytes,
  • Root-tuber geophytes,
  • Bulb geophytes, and
  • Root geophytes.
• Helophytes: rest in marshy or wet soil, e.g. reedmace and marsh-marigold; and
• Hydrophytes: rest submerged under water, e.g. water lily and frogbit.

These are annual plants that complete their lives rapidly in favorable conditions and survive the unfavorable cold or dry season in the form of seeds. Many desert plants are by necessity therophytes.

Tillandsia landbeckii, an aerophyte

Aerophytes were a later addition to the system.[12] These are plants that obtain moisture and nutrients from the air and rain.[13] They usually grow on other plants yet are not parasitic on them. These are perennial plants and are like epiphytes but whose root system have been reduced.[14] They occur in communities that inhabit exclusively hyper-arid areas with abundant fog.[15] Like epiphytes and hemicryptophytes, their buds are near the soil surface. Some Tillandsia species are classified as aerophytes.