The Genus Cordyline
This is a small genus of shrubs and trees native to warm climates in Asia and Australia, reportedly with one species native to South America. The names seem to be confused in horticultural literature. At least one species is cold hardy enough to grow in northern zone 8 gardens.
It is challenging to keep up with botanists’ changes to the Asparagaceae. The current trend in botany is to include several families previously separated from the Asparagaceae. This epanded family includes many interesting garden genera, including agave (Agave,) asparagus (Asparagus,) cast iron plant (Aspidistra,) spider plant (Chlorophytum,) ti plant (Cordyline,) plantain lily (Hosta,) mondo grass (Liriope,) nolina (Nolina,) snake plant (Sansevieria) and Yucca.
New Zealand cabbage tree
This is a small to medium-sized tree. It is capable of reaching over forty feet tall in the wild. Young plants have a straight stem that branches with age. Each branch is topped with a dense crown of slender, grass-like leaves. It is cultivated in warm temperate gardens around the world for its tropical appearance. Leaves vary in width and color. Several cultivars have been selected on the basis of leaf color. It grows best in a moist, well-drained, shady site and is moderately drought tolerant. It is listed as moderately salt tolerant, along with C. stricta and C. indivisa. Various references indicate that this plant will survive in 7b with protection but is more reliably cold hardy in zone 9.
Plants are available in nurseries and catalogs. ‘Red Sensation’ is an attractive plant with reddish leaves that maintains its best color in full sun. Plants are propagated by seeds and cuttings. Cultivars will not come true from seeds.
My largest plant grew to eight feet tall from a small potted plant in just four years. Young plants survived a brief winter low in the upper teens F with no obvious damage but all of my plants were killed by two particularly long, cold winters in a row with lows in the upper teens F.
This is an evergreen, tropical plant that grows to about six feet tall or more. The broad leaves are green, pink, or white variegated. Grow them in part shade or sun in a moist, well-drained site. Plants survive in uppermost zone 9a and even lower 8b through mild winters or in protected sites but they can look a bit ragged by spring. Various references say it is cold hardy from 9 or 10 to the equator.
Plants are readily available in nurseries and plant shops. Propagation is by seeds and cuttings. Seedlings may not have the same foliage color as the parent plant.
I grow plants in zone 9 as cold tender perennials that are annuals many years. I have seen plants survive mild winters in northern zone 9a, experiencing some foliage damage with lows in the upper 20’s F. Plant suffer stem damage and may be killed when temperatures drop into the mid-20’s.