What prompts growth ?

[JennieAtkinson]

Was wondering if I could start off broad beans (being relatively hardy) in the propagator and then get them into the polytunnel under plastic bottles in March. This would be two months ahead of my usual planting time. Presumably it is temp and daylight which prompts growth when coming out of the winter, but I wonder when ?

At the moment we have daylight from 8 am to 4.30 pm but once we get to the middle of Feb it really seems to pull out quite fast (we have to get to 24 hours daylight by mid June). Temp at the moment is about 3 - 6 degrees and only dropping to about 1 at night, so not much difference between day and night temps. (Although we have had snow this week!) We won't start warming up until end April/May, so I don't normally start any of my seeds off until beginning of May.

This winter the lettuce has grown slowly, but the swiss chard has kept bringing on new shoots and the leeks are bulking up, so the polytunnel is getting some warmth and daylight.

Any thoughts ?

[Nicos]

I was wondering about this yesterday after your posting on daylight!
I'm pretty sure it's warmth and length of daylight only (I stand to be corrected!) but then thought if it could be the quality of daylight- ie amount of UV in the light? If this was the case, you could try shining one of those UV light bulbs and see if it makes a difference. Maybe set up light reflectors in the same way as photographers do aswell / instead. Perhaps you could do a trial and have it published in GYO !!!

[nick the grief]

I use sheets of Polystyrene, these keep the cold from coming thru the sides of the g/house as well as reflecting the light.

I wouldn't have thought light would have made any difference as such as the seeds are buried & get none.

Temperature would be the trigger I guess (which I guess is sort of connected to daylight) and this will get the hormones kick in that breaks the dormancy. I guess thats why fridges/cold stores work for late cropping spuds & cold stored Strawberry runners.

[Birdie Wife]

I'm thinking that seeds which you bury are probably more affected by temperature than daylight, whereas seeds that you sow on top of the ground are more affected by daylight. So thereoretically if you keep your broad beans warm enough they should germinate in darkness. Although once they've germinated, you'll need light anyway to stop them getting spindly.

Could be wrong though, it has been known!

[andrewo]

Warmth germinates a seed and then the seedling searches for light and draws energy from the sun. To little light and the seedlings are spindly, too much and their scorched. 8 hours a day should get them off to a good start.

[Nicos]

Yes - I was thinking more about growth than germination. I think most seeds will start to germinate in either light or dark, but as soon as the radicle (root)appears gravity and light take effect.(You see I just knew those biology experiments in school of germinating broad beans pinned to a board would come in handy one day!! - just need to know why we tried to put maggots into the gas outlets for the bunsen burners ...oh...maybe I was just bored/hungover???)

[sandersj89]

But in nature there are always exceptions.

Some seeds need light to germinate, this is then a combination of both light and heat, though I suspect heat is the initial trigger.

Complicated things seeds!

Jerry

[Geordie]

How about water as the initial trigger?

[Nicos]

well spotted!

[sewer rat]

Or cold - vernalisation I think ?

[JennieAtkinson]

Havent' had a chance to even try yet! Shed including propagator been inaccessible due to the snow and the 90 mph winds rattled it so much (shed) everthing has fallen off the shelves! So alot of tidying before I start, but will try this weekend.

Lots of beans in the packet, so its worth an early try. Daylight hours are now good - light before I wake up at 6.45 am and probably light to 6.30ish in the evening.

Thanks for all your posts. Interesting .........