Cosmos: Beautiful and Easy

I start all my Cosmos inside with 72-hole seed trays roughly four weeks before the last expected frost. For me, the last frost is around April 15th, so I start sowing mid March. Once you are sure freezing temperatures are done for the season, you can set the plants outside. When the time comes, be sure to “harden off” the seedlings. This is where you slowly introduce the plants to direct sunlight in order to prevent them from burning. My recommendation is 2-3 hours of sunlight on the first day, increasing by roughly an hour each day for the next 7-10 days.

I try to wait for a cloudy day or two forecast before planting the seedlings (to further reduce the risk of burning). Dig your hole just deep and wide enough to plant the seeding, 12-18 inches apart. I always add a teaspoon of Espoma Bio-Tone Starter Fertilizer to each hole before I pop in the seedling. I’ll then water and add my first layer of floral netting approximately 6″ from the ground. Although you won’t need it until later when the plants get bigger, this seems to keep people, dogs and the occasional deer from walking through the Cosmo bed.

When the seedlings are 10-12 inches high, I remove the center 2-3 sets of leaves. This is known as “pinching” in the garden world (we do this with dahlias as well). It will cause plants to branch out and increase flower production.

Next, move the floral netting up, about 2 feet from the ground. Add another row of netting about 2 feet above the 1st row. Trust me on this, you will want the extra support in July.

Once you get blooms, continue to deadhead (i.e. cut the flowers) to keep the plants producing. You will enjoy huge bouquets of beautiful cosmos all summer!