Seedlings stalled

[Martin H]

Advice please...

On 1st March I sowed four pots of Brussels sprouts, four different varieties. I left them on the cold greenhouse bench with a propagator lid over them.

After a week or so they all germinated so I whipped off the lid to let them breathe.

Since then, two of the varieties have grown on nicely and are now ready for potting up individually in modules.

But the other two just stalled, like this:



I'm going to re-sow, so I pulled a few up to see what was going on underneath. Sorry the picture isn't very clear, but the roots have either curled up or not grown at all:



I've not had this problem before, when seedlings fail for me it's usually damping off

Obviously I didn't intentionally do anything different between the four varieties. Any ideas what went wrong so I can avoid in future? Dodgy seed, dodgy compost or accidental mistreatment?

Cheers!

[marchogaeth]

Dodgy seed, dodgy compost or accidental mistreatment?

I would say the latter. I would always sow different varieties in separate pots, I grow Flowers of Spring and Precoce de Louviers cabbages and they do behave quite differently even if it's only a few hours difference in germination time. I've also got a packet of mixed lettuce seed and it really annoys me when I have to thin them out because, if I did it logically, I would end up with all the same plants (the ones that are a bit bigger when the scissors come out).

Maybe when you looked at the whole pot of seeds these didn't stand out as different but really they were. It's either that or s()d's law! Why don't you let the ones you haven't killed grow on and see what happens?

[Kristen]

I think most likely reason is that the ones with poor root development are wetter / too wet.

[Martin H]

Thanks for the reply, Marchogaeth.

I'm not sure I was clear in my initial post, I sowed each variety in a different pot just for the reasons you outlined. So I had a really nice pot each of Evesham Special and Rubine, but a rubbish pot each of Trafalgar and Bedford. The pictures in my post are of Bedford.

[sparrow100]

Duff seed? If you've given them the same treatment, same compost, same watering, seed is the variable. I think sometimes (not always) we're too quick to blame ourselves for seedling problems. Was speaking to someone in HSL and they were saying that there are more instances of lower/hinky germinations in some seeds than others, depending on how long they were stored before being packed. And whether the seed packets had been in something like garden centre conditions before you got them.

[Kristen]

I think sometimes (not always) we're too quick to blame ourselves for seedling problems. Was speaking to someone in HSL and they were saying that there are more instances of lower/hinky germinations in some seeds than others, depending on how long they were stored before being packed. And whether the seed packets had been in something like garden centre conditions before you got them.

I'd be interested in other folks' views, but I would expect that to impact germination percentage, rather than the ability for a germinated seed to form a proper root?

[marchogaeth]

Thanks for the reply, Marchogaeth.
I sowed each variety in a different pot just for the reasons you outlined.

Sorry to treat you like an idiot! Some comments still apply if you treated all the pots the same way, though.

I'd be interested in other folks' views, but I would expect that to impact germination percentage, rather than the ability for a germinated seed to form a proper root?

Agreed.

[sparrow100]

I'd be interested in other folks' views, but I would expect that to impact germination percentage, rather than the ability for a germinated seed to form a proper root?

I wouldn't think it would be limited to that - duff seed can make weak seedlings. I don't want to labour the point, but germinating is a viability test not vigour. It doesn't follow that if a seed germinates it makes a strong seedling.

[marchogaeth]

Yes, we could go round and round or on and on. To me, roots like that suggest a check for some reason but that's based on my knowledge of sugar beet growing! (Which is quite possibly out of date.)

[WendyC]

Have you had any of those compost / scariad flies around? I think I'm right in saying their larvae eat roots. Not significant on an established plant but enough to stop a seedling.

[Martin H]

Have you had any of those compost / scariad flies around? I think I'm right in saying their larvae eat roots. Not significant on an established plant but enough to stop a seedling.

Ooh that's a thought. I have had some this season, I had always thought of them as harmless, but apparently not: https://www.rhs.org.uk/advice/profile?pid=804

I didn't see any little white worms in the compost when I emptied the pots; mind you I wasn't looking very hard.