Cosmos Seedlings Too Tall - Knowledgebase Question

Name: Walter W.
Williamstown, NJ
Question by waltknit
March 25, 1999
I am a fairly seasoned gardner and have been raising seedlings in the spring for many years. This year I planted tomatoes, daylilies, hosta seeds from my own plants and others. However I also planted 2 weeks ago, under my gro lights as always, a small flat of cosmos Burpees Versailles mix. I use a very small warming cable for gentle bottom heat and maintain a max distance of no more than 4 inches to the light bulbs which should produce short healthy plants. These cosmos were up and out of the ground in 30 hours and have continued to grow at a tremedous rate. They are only about 13 days old and they can no longer support their height of almost 6 inches. I am dumfounded.

Can I salvage these plants by planting them deeper than they are growing now or should I scrap them and plant outside later. The plants now have their first true leaves and could be replanted into larger containers.

PS. ( Gardening is always full of new surprises no matter how long you have been at it.)

Answer from NGA
March 25, 1999


Cosmos are so fast growing that they are difficult to raise from seed at home (without a greenhouse) and in my experience they are better direct sown as soon as the soil has warmed in spring. If they are outgrowing their starter pan or cell packs then you will need to transplant them quickly so they do not become stunted. You can transplant a hair deeper than they are growing now, but this may not be enough to help them support themselves. Once they have been transplanted, one way to slow them a bit is to keep them cooler, but be prepared to raise the lights quite high between now and when they can be set outside on sunny days for the sun they crave. Keep in mind, too, that they do not tolerate frost so you will need to be conservative in planting them out.

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