Yellow Sulphur Cosmos

Cosmos prefer well-draining soil that is of average to poor fertility. They are tolerant of a wide variety of soil types and pH but prefer slightly alkaline soils. Cosmos will produce the greatest number of flowers when planted in full sun, however they will tolerate some shade. Remove spent blooms to encourage the development of new flowers and water only as needed. Fertilizing is not recommended.

After danger of frost has passed, sow seeds 1/4" deep into a prepared garden bed. Can also be started indoors 4-6 weeks before the last frost. After germination has occurred, thin to one plant every 12-18". Do not over-water as this will reduce blooms.

Set plants outdoors after danger of frost has passed, spacing plants at least 12" apart in all directions. Keep adequately watered until seedlings are established but avoid overwatering as this can lead to problems.

Cosmos are generally very easy to care for as they are tolerant of drought and poor soils, however they can be affected by a few diseases, particularly during wet spells. Fusarium and bacterial wilt will cause the leaves to look wilty or limp. These problems are most common when the plants receive too much shade, too much moisture, or are planted too closely together. In rural areas, corn rootworm beetles can attack the petals in late summer and fall. Unfortunately, sprays are usually not effective at controlling rootworm beetles and pose the risk of harming bees and other pollinators.

Cosmos make excellent cut flowers, with individual blooms lasting 4-6 days and vase life extended by the gradual blooming of multiple flowers along a stem. Flower preservative is recommended to maximize vase life.

CONSIDERATIONS:

Cosmos seeds are relatively easu to save. Just wait for the flowers to mature into brown seed heads. Remove the seed heads and place in a paper bag until completely dry, then separate the seeds from the seed head and place in an airtight container until ready to plant.

HARVESTING SEED:

SEED LONGETIVITY:

Cosmos seeds will remain viable for up to five years when stored under ideal conditions.