Duration and habitat:
Herbaceous – these produce little or no persistent, woody tissue above ground. They have soft stems and do not have obvious bark. Herbaceous plants which persist for many seasons and flower every year are called herbaceous perennials.
Woody – having persistent, hard, aerial twigs. These usually possess obvious bark. They possess aerial, woody stems and twigs which can survive many winters. Their shoots may be any consistency, and they bear buds, helping them to grow further during favorable seasons. They may lack noticeable bark.
Annuals – They exist for one season, during which time the seed germinates and it grows into a plant which produces flowers, fruits and seeds, and then dies. All of this typically happens within a year. They typically have small, slender roots and most of the branches produce flowers, especially towards the end of the growing season.
Winter-annuals – Plants that germinate in autumn, pass the winter as small rosettes of leaves near the ground, and flower the following spring.
Biennials – These germinate in the spring and produce a rosette of leaves during the first year. They persist through the following winter and produce flowering shoots, seeds and fruits during the subsequent spring and summer. After this, the whole point dies off.
Monocarpic plants – They produce a rosette of leaves which do not flower immediately. Rosettes oftentimes persist for many years.
The plant bears flowers only once, following in the death of the plant. While this necessarily entails the death of the plant’s underground parts, the flowering itself oftentimes lasts for many years.
Climbers – these plants ‘climb’ things by structural means, such as tendrils. Vines are a well-known example of this phenomenon.
Parasitic plants – like animal parasites, they draw their nutrition fro their host plants.
Epiphytes – plants that grow on other plants without extracting its nourishment.
Saprophytes – instead of practicing photosynthesis, these plants draw their sustenance from the soil on which they grow.
Subshrubs – small, low plants, having thin, wiry, woody stems. While they look like herbaceous perennials, they can be distinguished by persistent, woody, above-ground stems. These are known as “suffrutices”, from which English-speaking botanists get the adjective “suffrutescent.”
Shrubs – larger, woody plants with obvious, persistent branches. They ordinarily have many main stems with arise at the ground, or at least near it. There is technically no scientific means of distinguishing trees from plants. Trees are usually larger with a distinct trunk or “bole”, which raises the branches above ground level, but other than this, humans ordinarily operate with a kind of folk distinction.
Cullen, J., and J. Cullen. Practical plant identification: including a key to native and cultivated flowering plants in north temperate regions. Cambridge, UK: Cambridge University Press, 2006. Print.