African marigolds from seed

A few years ago I grew some african marigolds from seeds in 3-inch pots, in a greenhouse. The seeds all germinated but the seedlings were all stem with little foliage. When I eventually planted them out, they collapsed. Before and since then, I've grown other flowers from seed, with reasonable success.

Recently I bought some african marigolds ready for planting out. They are great, really bushy, nothing like my seedlings.

Can anyone throw any light on what I did wrong when I grew them from seed ?

 

my guess would be you kept them in the greenhouse too long.

They probably got drawn up and grew very soft.

They need to be hardened off before planting out also.

 

Possibly the compost was lacking in nitrogen too.