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I am in the UK, midlands. Have these seedlings in a greenhouse and they were doing quite well. Almost getting ready to stick them in the ground for winter.

Almost overnight they have died. Can anyone note what the problem could be?

To much water? Not enough?

Temperature has been reasonable in the greenhouse, 16'C overnight. Warm days it can get up in the 30's but I open it up when its sunny to avoid it getting to hot.

I have been using a general feed for veg once a week. There is also a lot of slugs :/

Some pics, one thing that is strange is that it only seems to be the Brassicaceae family that is affected. The carrots in the second pic are still fine.

The third image is the same plants as the second image a couple days before.

Exhibit A Exhibit B Exhibit C

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Looking at your pics, I believe there are two things happening. I think you're overwatering ... they look long and leggy ... the plants collapse due to a small root system, caused by overwatering. When you overwater, the roots don't have to work hard so they stay close to the surface...watering less means the roots have to strive and grow deeper to find water. You want good strong growth above and below the soil. While water is crucial, don't throw water on them until the soil appears dry on top ... if you have good compost in the soil which retains water, you will not have to water as often. When you try seeds again, pinch off the top leaves once the seedling has three or four sets of leaves. This will encourage branching or widening of the plant. Another thing about good root development, the pics of your seedlings look like they should have been put in their own pots to get their roots established well, prior to putting them in the garden or containers. ... to transplant, you need strong roots, and that happens when the seedling has to push its roots down well into the soil to find water. Hope this helps.

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  • Thanks, seems to make sense. About the containers, those are just seed trays (these) with a couple seeds in each. Is there something better for propagation then?
    – dogmatic69
    Oct 22 '13 at 21:21
  • I done some more reading on the subject of over watering and it seems you were spot on. The soil has green tinge (moss / algae) and the leaves first went pale green before they flopped. Seems like it pretty common mistake :( Thanks for pointing me in the right direction
    – dogmatic69
    Oct 22 '13 at 22:23
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    Another thing, roots need air. You can drown plants, the roots have a fine hair system that attracts various bacteria and fungi in the soil. Plant growth is actually a symbiotic relationship between the three with the plant providing sugars and the others extracting nutrients from the soil to exchange for it. Slightly damp soil with air content is highly necessary for plant health, overwater and the anaerobic bacteria take over and the fungi die.
    – Fiasco Labs
    Oct 22 '13 at 23:14

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