As we head into the dog days of summer, the old fashioned orange cosmos becomes one of the most revered flowers. Botanically speaking it is Cosmos sulphureus and is a drought-tolerant member of the aster family from Mexico and Central America. Since we grow it as an annual, this gives basically the whole country the option of firing up the landscape.
If you haven’t looked at your garden center lately you will be surprised at how the flowers have changed. It is almost like they are glowing embers of fire, with shades of orange and golden yellow.
These awesome double or semi-double flowers will be prolifically produced the rest of the growing season. They attract bees, butterflies and the passers-by like me who become mesmerized at the blossoms. It is not uncommon to see the old-fashioned strains reach 6 to 7 feet tall by fall.
You can set out nursery transplants now or by all means plan on using them next spring. Seeds germinate quickly and will be blooming in eight weeks. Thin seedlings or transplants to 12 to 36 inches depending on variety. Add a good layer of mulch around young plants to help retain moisture and reduce weeds.
Deadheading old flowers will pay dividends with this plant as it gives the impression of wanting to bloom itself to death. Water the plant deeply during long, dry periods and give a mid- to late-summer pick-me-up with a light application of a slow-release, 12-6-6 fertilizer.
Blue or violet flowers make the best companions. To make the flower border sizzle, grow with salvias like the Mystic Spires Blue. Victoria Blue, and Cathedral Deep Blue varieties of Salvia farinacea would make wonderful partners.
There are a lot more varieties of cosmos than most gardeners realize. Planting by seed gives an option on variety selection. Bright Lights, a taller form in orange and yellow, is highly recommended. Cosmic Orange, a 2000 All-America Selection winner, and its counterpart, Cosmic Yellow, are shorter selections. Sunny Red, an All-America Selection winner from 1988, and the yellow version, Sunny Gold, are excellent dwarf forms, but getting harder to find.
The Lady Bird series is also dwarf. If you have the opportunity to try a new selection called Tango, it is almost iridescent, and stunning.
When you think about fall colors, orange and yellow are among the first that come to mind. The Cosmos sulphureus is among the best at providing these warm colors. Add a pumpkin or two, a bale of hay and a scarecrow and you’ll look festive for the season.