Cosmos (Cosmos bipinnatus)
A native of Mexico, also called Mexican Aster, Cosmos is a heat loving annual that provide abundant blooms all summer until frost. This airy plant produces tall, lanky stems with feathery leaves and colorful daisy-like flowers. The plants can grow up to 4-6 ft with dwarf varieties up to 1- 3 ft tall. The blooms come in assorted colors of white, pink, red, lavender and yellow, in single, semi-double and double forms making them an excellent cut flower.
Care
Grow them in full sun in a well drained, dry, poor soil. They thrive on neglect; rich wet soil will produce floppy plants with many leaves and little flowers.
Start them from seeds indoors 6-8 weeks before the last frost date or sow directly outdoors after the last expected frost.
To start the seeds indoors: Sow seeds and cover lightly with soil. Germination should take 5-10 days at 70-85 degrees.
Plant seedlings outdoors 9-24″ apart. The taller varieties of Cosmos should be planted in the back of the flowerbed and may need staking. To keep tall varieties from falling over, plant them 9-12″ apart, so that they can interweave and support each other. For compact, bushier plants with more flowers pinch them back once or twice before flowers buds begin to show.
Deadhead spent flowers for continuous bloom and to prevent them from self-seeding. If you want Cosmos to self-seed next year; allow some of the seed heads to remain on the plant at the end of the season. You can also collect dry seed heads for next years planting.
8 weeks ago I started cosmos from seed and they are now bushy and about 3 feet tall. They are in excellent soil in the center of my perennial garden — I thought I could fill in with a few annuals. However, NO BLOOMS. From reading above, I now understand that perhaps the soil is too good? Since I’ve never grown cosmos before, I don’t know what to look for. They look very healthy, but only foliage thus far. When should I give up on them?
Planted a packet of seed of Cosmos on an open well drained stoney (impossible) area in Southern Ireland. Absolutely fabulous display (ht.6 ft.) of all colours including white, but no yellow. Can’t find how to deal with seed heads to have seed for next year? Ann
I am in same situation as Lisa. The cosmos are grown in well drainage soil in PA. They have very healthy leaves, about 2-3 feet tall, no no blooms at all. I just feed them miracle-gro yesterday, which obviously is not a good idea.
So I shall neglect them for a while and I will see…
Is any part of the Cosmos edible?
I just started a packet of Cosmos from seed, I wasnt sure hoe many would start so I put good soil in a 1/2 gallon pot and started them all. Now there are all kinds in this tiny pot. So I guess im goining to try to sort them apart and plant them in my flower bed this afternoon. Perfect placce as it gets sun all day and the soil is hard light brown and not that great looking… we will see.
please can you tell me if i have to cut them back to the ground now that they have finished flowering.
Powdery mildew?
My Cosmo leaves and foliage have turned a milky white. The new blooms also seem to be a little weird looking. This has just happened in the past week. I have not changed the watering method or put any new fertilizer on them. Up untill now they have looked great and plenty of blooms.