A Debate: germinating Brassicas and other seedlings.

[dewwex]

Should Brassicas been germinated in darkness?.

I have germinated my brassica plants 2 ways this year.

1)early in year on a heat mat (13c min) in a glasshouse with a board on south facing side to partially shade.
2)lately in the house under the bed. and put on window for 12 hours once germinated, and then put into polytunnel.

I have noted that the house sown brassicas seem to be more leggy.

I have been sowing brassica plants for 3 years. And more and more i feel germinating in the dark produces more leggy seedlings. Does anyone share my view?

Has anyone found the ideal way of sowing Brassica plants. Lack of leggyness in brassica seedlings is very important in my view, other wise the small plants are not really strong enough to hold themselves upright. And don't make premo plants. twisted stems etc.

Maybe it is some other reason. like that its now too warm in a polytunnel for brassica seedlings during the day? or house temp of around 20c to warm for germinating brassicas?

Any body got any views based on experience?

I personnally would appreciate technical knowledge on the subject if it were forthcoming, as i feel its a fiddley subject anyhow.

[Jenny Green]

Any seeds left in darkness for any time after germinating will grow leggy. They're trying to reach the light. Too high temperatures will also cause legginess in plants that grow in a cold climate.

[cevenol jardin]

I don't grow brassicas for harvest in the summer months (too many other edibles more suited to our climate) all mine are for winter autumn spring harvest and i always start them off in a seed bed with a cold frame April & May & June with the light removed and plant them out to their final positions May-July. It works well for me, the seedlings don't get too much wind and don't get too leggy so long as i thin them a bit as soon as they are up. I've tried growing in modules and the plants suffer too hot and dry during the above months.
I have never tried germinating in the dark - what made you think of that?

[dewwex]

when i say germinating in the dark.i mean covering the modules with say newspaper. or if done in a house under the bed say.

most people or books i have read say cover the modules /pots etc with say newspaper and also advise putting in say clear bags to keep moisture in.

What are the actual reasons. I am rather getting skeptical about this advice. when we sow in the field we do neither. i can understand keeping pots shaded in regard to keeping down midday temps on say a window sil or in a propagator. But its not a rule so to speak. unless you sowing very shallow, i find it hard to believe that light is an issue, that would prevent germination.

[Johnboy]

Hi Dewwex,
There are several families of plant that will only germinate with full light however none of them are vegetables.
Brassicas do not need light to germinate but are best germinated without heat and with good light above. If you germinate them in the dark they will stretched in the germination before you can get them into the light and will only ever produce a weaker plant.
However there are three plants that I do deliberately germinate in the dark and these are Parsley, Celery and Celeriac. These are sown broadcast across the modules then germinated in the dark and when the first few germinate they are removed from the propagator and placed on the bench and those showing removed from the tray and full germination takes place within a week. So I initiate germination in the dark and then place them in full light on the bench in the tunnel.
JB.

[alan refail]

As far as I can see, all seeds that germinate below ground, whether in the field or in modules/pots/seedtray, are germinating in the dark and should not need any further darkness. When they emerge they presumably need light immediately in order to develop naturally.
The limited number of brassicas I now grow I sow in modules, pot on into 3inch square pots and plant our when roots just fill the pot. I have no leggy seedlings.

Alan

[Johnboy]

Hi Alan,
Quite so and the three that I mention are sown across the top of the soil and as they germinate they have Peat lightly sifted over them. For this reason the modules are not filled to the top prior to sowing. They are given 15C but none of these are Brassicas.
Brassicas do not need heat and to put them into a propagator is courting disaster. I feel that it seems that it doesn't matter how many times you stress this on the forum people will disregard what is said. I have been growing Brassicas since 1943 and I think by now I might just have managed to have got the hang of growing them.
JB.

[Primrose]

I sowed some purple broccoli indoors in February on a window sill. They benefitted from the indoor heat but I suspect the light level was too low. Consequently they grew so leggy that I had to toss them and start again. My next batch I germinated in my mini plastic greenhouse 3 weeks ago. They got more light and were exposed to some pretty high daytime temperatures for at least a week. They are peeping through now and the stems look so much sturdier that I'm inclined to think that exposure to adequate daylight, rather than temperature range may be the key to non-leggy plants. I'd love to know the process/temperatures which commercial growers follow to produce their plants for garden centre sale as the stems on their plants always seem to be much thicker than mine.

[dewwex]

It might be worth pointing out that there could be two forms of leggy seedlings in brassicas.

1)those germinated in dark which get stretched looking for light.
2)those who at germination look perfect, but seem to grow too fast later until true leafs form. heat??

issue 1) is a common occurance across veg, but 2) seems to be bigger issue amongst to brassicas.

I find i do have to pot up brassica seedlings as Alan does, sometimes.

this gives extra support to young plants stem. But i feel if i was growing correctly i should not need to do such. the commercial plants on sale are not potted into pots, and sometimes my plants do'nt get leggy so i don't have to do with these plants.

I have just sown new batch and left in cold frame with no covers a few days ago.. so i will let you know how i get on.

I still wonder whats the best depth to sow brassica's too, and whether this is an issue.

Advice from literature to back or packets can vary 1 cm to 2.5cm. which is it? what are the differances with a seedling grown at 1cm to that grown at 2.5cm. Anyone tested this?

i find it mine-field! Iritates me somewhat.

[dewwex]

Primrose:
Can i ask why are you sowing 'purple sprouting broccoli' in febuary? when traditionally sowing is not started till april/may. Whats the advantage/logic?

[dewwex]

To cevenol jardin:
what do you mean by 'light removed'?

[dewwex]

Shading.

the following is my hunch.

Shading probably does make sense say in a tunnel or greenhouse to reduce day time peak temps. So say early on in year(eg:early march), with say brussel sprouts. i put on a propagetor set at 13c min temp. i semi-shade drom the south with a big piece of cardboard behind the propagtor. Then down to polytunnel once germinated, and full light. I had good results.

late april/May (this year)though i feel is too warm in a polytunnel/greenhouse anyway, so issue of shading does not apply i feel!ie. the ambient air temp is two high from the start.

Its quite common to hear advice on ideal temperature ranges for say tomatoes. eg 16-36?c

But very little is given on other non 'greenhouse' type crops.

Oh i forgot, we in the dark ages!!

Or maybe its just down to the 'commercialisation of thought'

[dewwex]

I reply to Johnboy:

So if you were starting off say a batch of 'F1 hispi' summer cabbage in early febuary you would not put on a propagtor.

You say that 'Brassicas do not need heat'. I am going to be a bit nit picky here, but do you start in tunnel or polytunnel. surely that is heat?

which starts me thinking is there a difference in terms of effects of temperature on plants at night as opposed to day. A propagator gives steady heat, wheras a polytunnel or greenhouse only supplys really daytime heat.

Is there not premature bolting issues regarding growing a few brassicas in cold conditions. eg chinese cabbage, other oriental brassicas, and i suspect Annual forms of sprouting broccoli.

[alan refail]

Dewwex

You're now debating with yourself If you wait for some replies you might get something useful. I got lost half-way through your last five consecutive posts. There were some comments I wanted to make on each, but while reading the next post I forgot, and so on. Just one answer:

"To cevenol jardin:
what do you mean by 'light removed'?"

The top of the cold-frame, known as the light.

Cofion gorau - regards

Alan

[Primrose]

Dewwex, You are right about me sowing purple broccoli in February. It was far too early and I guess my enthusiasm just got the better of me. It expect it was just a fine sunny day, I felt the sap rising within me and probably just couldn't curb my enthusiasm to get busy and sow something! Seriously though I have sometimes found that a few early sown plants have grown enough by July/August for me to sneak a few leaves off them for cooking, before all the white cabbage butterflies arrive and start sabbotaging the leaves.