Cosmos sulphureus
2007-09-21. Differing habits of Cosmos sulphureus despite being from the same seed packet and planted in the same site.

September 21st, 2007
Cosmos, the Tall and Short of It

I planted a packet of orange cosmos, Cosmos sulphureus, early last summer and the seeds sprouted and grew during our very rainy June. When I returned from vacation in July, the meadow was populated with lots of cheerful orange flowers growing on plants with a branching habit about three feet (1m) tall and wide. Those plants are just now starting to look a bit ragged.

In their place Super Cosmos has sprung up. These are orange cosmos on an incredibly thick stalk. The first one shot up to almost 6 feet before flowering. I had to stake it, as it was leaning precariously. I thought this was just a freak but all the orange cosmos coming up now are following the same pattern.

All these cosmos were planted at the same time from the same seed packet in the same location. I have not fed them anything. (Most wildflowers thrive on poor soils; feed them and you’ll get a lot of green and few flowers.) I have not given them supplemental water, as we’ve had so much rain this year. And yet they look like different plants. Were there different varieties in the seed packet? Did the early sprouting type have a different habit. Are they responding to the different amounts of rain we received at different times over the summer? Or did the ones that sprout earlier grow differently because of the time of year they were growing? I read once that cosmos grow best after the summer equinox. Certainly the plants that sprouted before the equinox behaved quite differently than these that sprouted after.

This is the first year I’ve grown orange cosmos. (Pam/Digging assures me it won’t be the last as they are prolific self-sowers.) So I have no basis for comparison. How do your orange cosmos grow? Short and wide? Or tall and straight?