Broad Bean Germination Woes

I have sown some broad beans [var Karmazyn] and some of them are emerging. They are at the stage where the buried head is lifting from the soil and unfurling so the shoots are trying to stand up straight but some of them are failing when the first leaf bud is half open. They are going black at the "neck" at the base of the leaf bud at the top of the shoot which is about 1 cm or so above the soil. The rest of the shoot down to the soil and the leaf group are light green but on some the leaves themselves are going black and rotting away. It looks like the sort of mush that I'd expect from frost rather than a dry shriveling.

I have attached photos to show 2 seedlings adjacent to each other in the same pot. The first one is about to drop and the second one is OK so far. I have included that because I don't know if the dark pigment at the neck is normal for this variety or if it's early stages of failure.

There have been no frosts during germination and the weather's been quite warm this April. They are in an old caravan used as a potting shed and moved to nearer the window for light once emerging. It didn't get too hot and I opened the other [mesh-screened] window for ventilation on the hot days. There is no direct sun this side. They have been kept well watered and there are no slugs or other known pests in there. They are sown in a rich leaf mold compost harvested on-site.



If anybody knows what might be causing this then I'd be most grateful for the heads-up.

Thank you.
X

 

Not seen this before. The only thing I can think of (guess) is the leaf mould. I’m not sure, but I think that some leaves aren’t suitable. Have you used it in the past?

 

Hi Freddy; thank you for the reply. I have used this sort of leaf mould previously for growing saplings I rescue and keep in pots until I find somewhere for them and for re-potting other things but not for veg or for germinating veg seeds. It was harvested from years of buildup. There will be a lot of beech in there with sweet chestnut, oak and birch that are growing in that part of the woods but there might have been other species before that have died out. There will also be other stuff rotted down like wood that was too rotten for firewood and the usual sundries such as beech mast cases, chestnut cases etc. The more recent surface leaves were raked away first then the mould was loosened with a mattock. It was sieved with quite a coarse mesh mostly to get rid of thin fibrous roots that were starting to exploit the pile so there are still some beech cases in there.

 

Just wondering if the growing medium actually contains any soil, leafmould is good, but I dont think on its own its great for growing plants, it needs to be mixed with soil.
I think it could be very acidic, which I dont think Broad Beans will like.

Having said that the picture looks like some kind of fungal problem, how many are looking like that?

You do sometimes get a few duff seeds when it comes to beans, that tend to germinate but are rotting at the same time, if you get my meaning.

 

Hi Pete; thank you for the reply.

Yes, there might be a deficiency of the desired minerals etc as it's collected from places where I stopped before the gritty layer as I didn't want stones. To my novice, untrained eye, the stuff from deep down looks like soil. Some the leaf mould will be 100 years old [*]. I wrongly presumed that there must be a point that it becomes classed as soil. It's a bit of an experiment but I get black currants, apples and other tree crops. It's a disadvantaged site because some of it is old granite quarries so we're reclaiming/restoring land where the quarrymen have strewn chippings and shards from the bankers on the level. They've formed a handy terrace that juts out from the slope and catches more of the sun. Maybe I will have to do some PH manipulation.

Most of the bean seedlings seem to be failing so I dismantled a couple of the pots. They seem to have a natural redundancy plan as they are putting 1 or 2 new leaf buds out of the bean at the base of the failed shoot. I did not see these before dismantling as they were still underground. I was half expecting the bean to have been consumed by now but it still has a lot of body so maybe it's got enough reserves to succeed at a second attempt. I think the beans have sunk deeper than 2" since I planted them although I can't think how they'd migrate downwards. The new buds/leaves do not have the dark pigment. I get the feeling that the problem might be caused by them having their heads underground for too long in contact with wet compost and that it's a combination of wetness and depth/time. Maybe I'm simulating waterlogging as that leaf mould seems to hang on to its moisture better than I expected.

So I've carefully manipulated a few of them to place the bean and those 2nd shoots near the surface so they have less time to rot. Time will tell

[* Calculated from the last known disturbance. This batch was collected from ancient quarry/woodland tracks rendered inaccessible by a later quarry truncating the track as the quarry was enlarged. The tracks are cut across a steep slope. The leaf mould collects in the upper quarter of the track and tries to make it into a slope again. It is harvested in the course of track restoration.]

 

Think I'd just get a bag of multi purpose for germination at least and then mix your leaf mould in with the garden soil when planting out.

Leaf mould never actually becomes soil its organic matter that tends to disappear, soil doesn't disappear as it is usually a mixture of clay, sand, grit, silt and minerals etc.
But for good plant growth, especially with veg, you need a combination of both.