The Hampton Gardener takes on the cosmos

I can always depend on a certain phone call around the end of the summer. Sometimes it’s toward the end of August, but it can happen in late September.

A dutiful reader is sorry to bother me (it’s no bother) but he/she has got the most unbelievable cosmos growing in the garden. It may be orange or reddish, maybe even pink, but it’s not the color that the caller is so excited about. The source of marvel is the fact that this reliably tame annual that usually grows about 2 to 3 feet tall has managed to top the 7-foot mark and “isn’t this very rare or unusual?”

While each gardener would like to know that this “unusual” event is rare and specific to their garden, their adherence to moon phases or the use of hummingbird guano, the fact of the matter is that many cosmos will exhibit genetic diversity with an occasional, exceptionally tall plant.

But aside from this infrequent mutation, the cosmos are a great and easy annual to grow.

Too many gardeners think of cosmos as they were used in their grandmother or grandfather’s garden—tall, sprawling plants that needed staking and were relegated to the back of the border or hidden in the cutting garden. However, breeding efforts in the last two decades have resulted in many new varieties that have been downsized, while retaining their airy and colorful qualities.

In fact, the new cultivars are so various that an annual bed or cutting garden can be crafted solely with cosmos and yet retain a diverse look. The plants may be tall or short, produce single or semi-double flowers, and have petals that are daisy-like, quilled or anemone shaped. The cosmos color palette begins with pure white, shades into all the pastel hues and ends with bright yellows, reds and oranges.

Like many of our warm weather annuals such as dahlias and marigolds, the cosmos originated in Mexico and South America. Spain plays an important role in the introduction of cosmos to Europe and this is the apparent result of a 1788 expedition by King Charles III. After the expedition, several years were spent identifying and cataloging native plant forms known to Europe, though it isn’t clear if any of these continental types made it back to the colonies. But if we watch the path of American horticulture at that time, we have to assume that there were introductions and seed exchanges.

Latino priests grew cosmos in their mission gardens in Mexico. The evenly placed petals led them to christen the flower “cosmos,” the Greek word for harmony or ordered universe.

In 1897, the Plant Introduction Center in Washington, D.C. was searching for plants adaptable to American growing conditions. They brought the cosmos north of the border where it became known as the Mexican aster.

For our purposes, there are two species of annual cosmos that we grow here on the East End—the

Cosmos sulphureus

and the

Cosmos bipinnatus

. These two types are easily differentiated by leaf structure and flower color.

The leaves of

Cosmos sulphureus

are long, with narrow lobes and hairy margins. The flower colors of this species are always shades of yellow, orange or red.

Cosmos sulphureus

is the native species and can range in height from 4 to 7 feet, but the cultivated varieties (those in catalogs) are not as tall. The flower heads are composed of disc and ray flowers similar to the daisy form. The disc, or center of the flowers, is yellow. The ray, or outer petals, range from pale yellow or mustard to orange-scarlet. Red is a relatively recent addition to the color range and was first offered in 1966.

While you are browsing the seed racks or catalogs you’ll probably notice that

Cosmos sulphureus

is referred to as Klondike. The name dates back to the 1920s when shorter cosmos of only 3 to 4 feet became commercially available. The cosmos had gold flowers and was named Klondike after the gold rush in the Klondike River Valley in Canada. As years went by, the old Klondike was improved and newer cultivars introduced.

Cosmos sulphureus

contains both tall and short varieties. Some of the earlier varieties include the sunny series, the diablo series and the bright lights series.

The sunny series is a group of dwarf Klondike types ranging in height from 1 to 2 feet. This early, free-flowering series is available in gold or red and has semi-double 2-inch flowers.

The diablo series has 2-inch semi-double flowers of a bright scarlet-orange on bushy plants. This variety will grow from 2½ to 4 feet depending on the soil conditions and how early it’s planted.

The bright lights series is slightly taller and comes in a mixture of lemon yellow, gold and orange-red. This is the first cosmos with a full color mix that has a uniform blooming period and uniform plant characteristics with semi-double flowers.

The

Cosmos bipinnatus

has leaves that are finely cut into threadlike segments. The foliage on this flower looks similar to ferns and sometimes they are called the fern-leaf cosmos. The flowers are white or various shades of pink to dark red.

Cosmos bipinnatus

can reach a height of 7 to 10 feet, but most cultivated varieties are considerably shorter. The flower heads can be 4 to 6 inches across the bloom. The center flowers (disc) are yellow while the outer (ray) petals are white, rose, pink or crimson.

The

Cosmos bipinnatus

comes in a variety of series including the sensation series, the seashells series, the sonata series, the anemone series and the candy stripe series. The sensation series is ideal for the back of the border and for cuts. Although it grows to 4 feet, the plant is graceful in appearance with large flowers rising above lacy foliage. This variety is available as mixed colors and as straights in crimson, rose or white.

The seashells mixture has an unusual flower form. Its petals curve in on themselves, giving the flowers a rolled, quilled look. The mix contains rose and pink shades as well as white and bicolors.

The sonata series is of medium size, about 2 feet, and has a free-flowering habit producing pure white flowers.

The anemone cosmos are early-bloomers that have unique double crested flowers of an anemone form in white, pink and crimson.

Possibly the most unusual variety of

Cosmos bipinnatus

is the candy stripe series, which has white flowers that are striped or edged with crimson.

Now that we’ve got the basic types of cosmos down, next week I’ll talk about sowing the seeds and growing the plants. I’ll also talk about my personal history with cosmos and the 6 acres we planted a few summers back.

Keep growing.

Andrew Messinger has been a professional horticulturist for more than 30 years. He divides his time between homes and gardens in Southampton, Westchester and the Catskills. E-mail him at: Andrew@hamptongardener.com. The Hampton Gardener is a registered trademark.