Enjoy some colors in Spring : Grow Cosmos flower from seeds

I live in a city apartment. Fortunately, I have a huge terrace which is a miracle of 80' Taiwanese architecture, but it is by a main street and facing a shopping mall. I have ugly views from the terrace plus noise from bus, cars and crowds. However, my terrace has some sunlight and still in a good condition. It is not a place to stay and enjoy fresh air but we can see the terrace from every window of the apartment. If I plant something on the terrace, we will have some green natural view. It will still be cool!


To avoid damaging the building, we only do potted plant. Most plants had been in the terrace before I moved into this apartment. I am happy to have them because these big potted trees attract birds. I regularly add some humus made by my composter machine (icomposteur) from daily food scraps to feed the earthworms and I see birds keep coming to my terrace. Basically turtle doves, bulbul and magpies, they chirp every morning on my terrace! I even found a bulbul's nest on a big fig tree.

nest of bulbul on a fig tree

The climax of my terrace must be the cherry tree that I have planted six years ago. I bought it from a nursery center with low price. Now I have cherry blossoms !

Cherry blossoms

However, I would like to see more colors. So I pictured the scene that I would like to see. Surprisingly, that is a field full of with cosmos flowers.

So I bought cosmos seeds from online sellers, I don't know if they are reliable seed supplier, but cosmos seed is very cheap. Germinating seeds is always highly species-specific, which means every species is different. I am tired of Googling the particular instructions of sowing cosmos seeds and got myself distracted by the advertisement again, so I decided to sow the seeds with some intuitions I have acquired from graduate school. Of course, I failed few times.

cosmos seeds


My First attempt:  Paper seed starting trays with potting soil, place outdoors. (Fail)

I sowed cosmos seeds by placing them under potting soil in paper seed starting trays, they germinated nicely within 5 days but I failed to keep them alive because I was away from home for only two days. When I was back, they already died and the seed bed is dried. I guess the paper tray is too shallow and also water evaporates fast from paper. Paper tray can't keep moisture. Thus, the seedlings died.

Second attempt : Plastic planter with soil, place outdoor (Better)

I switched to a deep longer plastic planter and think I can skip transplant the cosmos seedlings later. I simply use garden soil. Seeds germinated in 4 days, but they looked unhealthy for I didn't expose them to sunlight right after the first green leaf showed up. Even I placed them under the sunshine later, but those seedlings still look bad. Not sure if they are going to make it. Poor.

Third attempt : Within container trees (Succeed!)

I sowed cosmos seed just on the topsoil of potted trees, for example, a eucalyptus and an ash tree, without any seedbed preparation. Fortunately, these seeds germinated in 4-5 days and keep growing healthily.

 To Grow Cosmos flowers from seeds :

  1. It doesn't require any special skill or knowledge.
  2. Do it in spring, 15~25 degree Celsius (59~78 F), the temperature fluctuation didn't kill my cosmos seedlings though we had a few days below 15 degrees while the seedlings were still tiny.
  3. Don't use paper seed starting tray. Water goes off quickly from paper tray and there is no way to keep them persistently moist.
  4. If you get seeds from a reliable source, Cosmos seeds should germinate within 7 days. However, some seeds could take longer to germinate. I have seen seedlings came out 21 days after sowing.
  5. They need sunshine right after you see the first two green leaves, place them under sunshine or they will be weak.
  6. They are good cover plants for container trees.
cosmos plants

Enjoy Cosmos !

cosmos flower