Unit 56 (056)

1. Compositae or Asteraceae, the Composite or Aster Family

The Compositae has over 1,100 genera and over 20,000 species. It is considered

to be the most advanced family of dicotyledons. It comprises herbs, shrubs, or trees

and is cosmopolitan in distribution. It is best represented in temperate or subtropical

regions that are not densely forested. The herbaceous habit is predominant, with lots

of shrubs as well, and the tree habit is rare.

About 20 % or more of cultivated ornamental plants are from the Family Compositae.

The flowers are arranged in a head with a large base or receptacle, which has its

involucre or base made up of a series of bracts called phyllaries. These bracts are

fleshy and are the edible part of the artichoke (Cynara scolymus).

The flower petals are tubular or ligulate (strap shaped). Because the compositae head

is composed of many small flowers, the individual flowers (= the petals or a dandelion)

are called florets.

The flower sepals or calyx is replaced by a pappus of scales, awns, or bristles.

In a typical flower head the outermost florets are ligulate or strap like and are called

ray florets, which are sometimes absent.

The inner florets are tubular and called disc florets. These are the small flowers in the

yellow center of the dandelion.

The fruit is an achene which is a dry fruit with a single seed. Achenes are also the

little “seeds” present in strawberries, which are in the Rosaceae or Rose Family.

The Compositae or Asteraceae were divided into two subfamilies, each with a number

of Tribes. Taxonomists now divide the family into a lot more subfamilies.

2. Plants in Unit 056; Dusty Millers

The genera covered include the first part of the alphabet, along with many silver or

gray plants that are often called dusty millers. Senecio cineraria is the common Dusty

Miller with the thick gray felty leaves. A finer more dissected leaf is found in

Chrysanthemum ptarmiciflorum or the Lacy Dusty Miller.

Look at Onopordum acanthium which is the Scotch Thistle. It is a 6 to 8 foot tall, thistle

like plant that is cottony gray in color, and has winged stems..

An interesting garden plant is the Japanese Plumed Thistle (Cirsium japonicum), which

has attractive red, pink, or purple flower heads.

Artemisia includes many gray or silver colored garden plants. Some western species

are the common sagebrush. A few species have medicinal uses, and some are

poisonous.

Artemisia stelleriana have very finey divided gray or silver leaves, with the cultivar

Silver Brocade having wide gray lobed leaves.

3. Chrysanthemum; splitting and lumping or species in a genus

Chrysanthemum as a genus has been split into a number or other genera, and you will

see this in the synonyms.

The splitting or lumping of species is based on the research of plant taxonomists, but is

not binding law. You can choose to use the set of names you prefer. There is no right

or wrong, but it is a matter of scientific opinion. Unfortunately, many horticulturalists

tend to use the new names immediately, while many reference books retain the older

names. Synonymy needs to be listed, which is missing in many books and catalogs.

This is why I use Hortus Third and The New Royal Horticultural Society Dictionary of

Gardening as a standard for names. They are comprehensive and widely used.