By Ralph E. Mitchell
As you are planning your annual flower bed this year, one that I have really had good success with in Charlotte County is Cosmos. This annual flowering plant comes in many sizes, shapes and colors. Originally from the southwestern United States and Mexico, Cosmos are not only sun-lovers, but also do well in our sandy, low fertility, soils.
The Common Cosmos or Cosmos bipinnatus is the type most often offered in seed catalogs and garden centers. This Cosmos can grow from three to six feet in height and has fine thread-like leaves. Cosmos plants tend to be very open and sprawling with weak stems that sometimes need support in the form of stakes. Large growing Cosmos provide excellent cut flowers and can be used in the landscape as long as you stake them. Early pinching can help somewhat as this helps promote a bushier and denser plant.
There is generally an excellent selection of Common Cosmos at your local seed rack or catalog. Some cultivars to look for are included in the various “series” such as Imperial Pink, Sensation, Sonata and Vega. ‘Sea Shells’ actually has curled petals that produce unique, tube-like shapes. Some Common Cosmos cultivars even have double petals.
Another species of Cosmos, Cosmos sulpureus is also available. Also called the Orange Cosmos, it has orange and yellow flowers. The foliage of this Cosmos is a bit more feathery than the Common Cosmos. I tend to favor the orange flowering types and have tried both dwarf (‘Cosmic Orange’) and large varieties such as ‘Bright Lights’.
While you may be able to find some started plants at local garden centers, I most often locate seed packs of selected Cosmos to start my own plants from seed. Cosmos are extremely easy to start from seed either as transplants or planted directly from seed just where you want them. In fact, Cosmos are often found in wildflower mixes and, in some communities, I have seen them planted along highways in colorful drifts of pink, lavender and white colors. Cosmos can reseed themselves and this makes them ideal for those looking to establish a “mini-meadow”. The site you select for your Cosmos planting should be in full sun; well-drained, but of low fertility. Too much fertilizer will actually cause the plant to produce foliage at the expense of flowers. Cosmos seeds will germinate in as little as one week. From seed to the first bloom, Cosmos will take from eight to twelve weeks. Plant or thin Cosmos to about eighteen-inches apart for best growth.
With bright and easy-to-grow flowers and ability to thrive in difficult growing conditions, all types of Cosmos belong in your garden! For information on common flowering annuals and perennials suitable for growing in our area, please call our Master Gardener volunteers on the Plant Lifeline on Mondays, Wednesdays and Fridays from 1 to 4 pm at 764-4340 for gardening help and insight into their role as an Extension volunteer. Don’t forget to visit our other County Plant Clinics in the area. Please check this link for a complete list of site locations, dates and times – https://blogs.ifas.ufl.edu/charlotteco/files/2018/03/Plant-Clinics-Schedule.pdf. Ralph E. Mitchell is the Director/Horticulture Agent for the Charlotte County Extension Service. He can be reached at 941-764-4344 or firstname.lastname@example.org.
Gilman, E. F. (2014) Cosmos bipinnatus ‘Sonata White’, Mexican Aster. The University of Florida Extension Service, IFAS.
Gilman, E. F. & Howe, T. (1999) Cosmos bipinnatus . The University of Florida Extension Service, IFAS.
Scheper, J. (2005) Cosmos binpinnatus. Floridata.com, Tallahassee, Florida
Scheper, J. (2003) Cosmos sulphureus. Floridata.com, Tallahassee, Florida