Starting seedlings under lights

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Starting seedlings under lights
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wellington womble

Joined: 08 Nov 2004
Posts: 15051
Location: East Midlands

Posted: Sun Jan 03, 21 10:25 pm Post subject: Starting seedlings under lights

I’d love a greenhouse, but realistically there’s nowhere to put one here. Last year I had a go at a hydroponics set up in the spare room, and it flopped. And I got water everywhere, and we couldn’t have any guests (2020. Not a big deal, in hindsight)

But I did raise some super seedlings under the lights, and given that I’ve nowhere for a greenhouse, I’m pondering the idea that it’s easier to light a dark space than heat (or enclose) a light one.

So I’m thinking about getting a few more growlights for the garage. Don’t really use it, except for storing junk. Can’t even put the car in it, because the camper needs to go behind it.

Anybody done anything similar, or have Thoughts? I’m primarily wondering how much heat I’ll need. It’s a single skin garage, so I’m not sure if just heat mats will be enough. I’m vaguely pondering an insulated cupboard around a shelving stack or something similar. I’d even be up for buying a kit, if I can find something the right sort of size (cheaper than a greenhouse, too)

Mistress Rose

Joined: 21 Jul 2011
Posts: 15996

Posted: Mon Jan 04, 21 7:58 am Post subject:
No experience of it, but doesn't sound a bad idea. You would need to insulate the area though I would have thought, and you will have to harden off the seedlings before putting them out.

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Mon Jan 04, 21 11:41 am Post subject:
I'm going to be putting together a talk about this for sometime in February. Would probably be good for me to work through any questions you have specifically!

dpack

Joined: 02 Jul 2005
Posts: 46247
Location: yes

Posted: Mon Jan 04, 21 1:37 pm Post subject:

Ventilation, internal and through flow
pest/disease/fungal control, can be a big one, best planned for
electrical safety, very big one.
heating may not be an issue, cooling might be even with LED kit in a confined space, see ventilation etc

moisture levels in soil/media need close control and are different for different plants
hands on matters, shadow of the gardener and all that so access to all the grow trays etc is needed at the planning stage

as kit has improved the ability to change the spectral composition of the lights to suit the objective that day is rather nice, see led kit

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Mon Jan 04, 21 1:52 pm Post subject:

It's always fun to agree with and contradict dpack. Consider temperatures for germination versus seedling growth. Can you geminate somewhere small and very warm and then grow somewhere bigger that doesn't require as much heat? (A bit species specific, so ideal situation is warmer and cooler spots for different crops) Avoid day/night temperature swings as they exacerbate legginess.

I wouldn't bother spending money on fancy lights unless you're trying to do a full indoor grow. You just need cheap LED shoplights to provide lots of light for little power, for the first few weeks of the plants' lives. Reaching peak photosynthetic efficiency through expensive LED setups won't really be noticeable (would maybe have them ready to be planted out a day earlier - why not just seed a day earlier?)

Last edited by Slim on Mon Jan 04, 21 1:55 pm; edited 1 time in total

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Mon Jan 04, 21 1:53 pm Post subject:
Consider an oscillating fan, both for ventilation and making the seedlings hardier and used to air flow so you have less hardening off to do (or simply get a greater success from it)

dpack

Joined: 02 Jul 2005
Posts: 46247
Location: yes

Posted: Mon Jan 04, 21 4:29 pm Post subject:
small can be even more tricky to control conditions re the lights, for the first couple of weeks a very basic rig is fine for seeds or cuttings, through a full growth to harvest cycle needs a bit more sophistication fan in the space+in/out ventilation is good, if you use a gallon of watering water it needs to go somewhere

wellington womble

Joined: 08 Nov 2004
Posts: 15051
Location: East Midlands

Posted: Mon Jan 04, 21 5:10 pm Post subject:

I’ve actually already got three lights. I was vaguely thinking of getting one more and adding them to one of those mini greenhouse thingummies. I’m just not sure how warm the garage is (not terribly, I should imagine. I doubt it freezes, but I wouldn’t think it gets into double digits before may, either.)

So said growhouse is going to need some insulation, and heat mats, I reckon. I think that will be enough. I usually germinate seeds in small trays in the house, and then prick out into modules so it’s the modules that will go in them.

The heat mats are all the wrong sizes, naturally. I’d wondered about boxing it in with rigid insulation with a vent at the top (doesn’t need to be waterproof) and a fan at the base. But I’ve no idea what sort of temperatures to expect.

Why can’t you ever find a thermometer when you need one?

dpack

Joined: 02 Jul 2005
Posts: 46247
Location: yes

Posted: Mon Jan 04, 21 5:28 pm Post subject:
amazon have a selection of greenhouse thermometers from about ten quid

wellington womble

Joined: 08 Nov 2004
Posts: 15051
Location: East Midlands

Posted: Mon Jan 04, 21 10:31 pm Post subject:

dpack wrote:

amazon have a selection of greenhouse thermometers from about ten quid

I know, but I must have three or four weather stations somewhere around.

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Tue Jan 05, 21 1:44 am Post subject:
I've got a soil probe thermostat for my heat mat, probably the best place to set the temp. LEDs can still generate a fair amount of heat as well, even though they're efficient - in an insulated space

Mistress Rose

Joined: 21 Jul 2011
Posts: 15996

Posted: Tue Jan 05, 21 8:39 am Post subject:
That's interesting Slim. I didn't realise that the fluctuation in temperature between day and night affected legginess. I always assumed it was trying to get to the light.

dpack

Joined: 02 Jul 2005
Posts: 46247
Location: yes

Posted: Tue Jan 05, 21 8:57 am Post subject:

wellington womble wrote:

dpack wrote:

amazon have a selection of greenhouse thermometers from about ten quid

I know, but I must have three or four weather stations somewhere around.

like my claw hammers and tape measures, i have plenty, but they hide

seconded that led and lp fluorescent lights do give off heat, not as much as incandescent or hpmh bulbs(the latter are amazingly warm)

re temp control, soil in trays or pots is not as good a heat sink as a large nutrient reservoir or similar but a few large containers of water will serve as a decent "ballast" to assist your temp control
that might be 3 lt pop bottles or 1000 lt drums depending on scale

from seed/cutting to ready to plant out is fairly small and only involves a little transpired/evaporated water but humidity /ventilation control is still important

you need to balance heat in, water in, fresh air in+all of those out in order to create perfect and stable grow conditions of humidity and temp.

timing the lights is easy but has a dramatic effect on the outcomes

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Tue Jan 05, 21 12:31 pm Post subject:

Mistress Rose wrote:

That's interesting Slim. I didn't realise that the fluctuation in temperature between day and night affected legginess. I always assumed it was trying to get to the light.

It is largely the plants reaching for light. But if you provide enough light, or are just measuring with a constant light level, you'll see the temperature differential also has an effect. I know this is true with tomatoes, I'm assuming also with other common crops, but can't promise.

wellington womble

Joined: 08 Nov 2004
Posts: 15051
Location: East Midlands

Posted: Wed Jan 06, 21 3:01 am Post subject:

dpack wrote:

you need to balance heat in, water in, fresh air in+all of those out in order to create perfect and stable grow conditions of humidity and temp.

Yes, I think it might be a bit of a pita. I can’t find anybody doing it either (what is the internet coming to!). Systems are usually designed for spaces that already have stable heat (micro greens in American basements, usually)

Perhaps I’ll go back to the spare room, as the heat is stable. It just feels weird, and it’s not designed for sloshing water about in, plus then there’s no room for the laundry. I don’t suppose we’ll be having any guests this spring, at least! Humidity hasn’t been a problem there so far.

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