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Effective germination is affected by temperature, humidity, light/dark. The literature says that making these conditions ideal can make massive differences in germination percentages & speed.
These are some of my attempts to control those variables. Part of the idea here is that I'm doing a mulch cover on the garden, so I can't just plant seeds. I grow them inside: Germination chamber until they sprout, then in InDoorGreenHouse, then in window racks, then harden to outside weather, then plant when they are well on their way, & can poke up above the mulch. It also makes better use of the garden, because the plant already has a 2-4 week headstart from where it would be if it was seeded directly into the garden. Combine this with insulating protection of mulch cover, row covering, hoop house, & heating coils under the raised beds, advanced succession planting, & it makes for several more crops/yr out of the same space. Also, this is part of the indoor winter gardening endeavor.
Germ1
Germ2--
--SETUP----Just a tub with water in bottom & a piece of 1/2" PVC screwed to each end, on which 3 metal tubes rested. This is what the 10"x10" half-tray sat on, just above the water. This could hold only one 1/2 tray, which could be (16) 2" soil blocks, or (120) 1/2" soil blocks. The round white thing you see is a cheap dial thermometer.
--Heat Source--seedling grow mat underneath & 10w aquarium heater.
--Humidity--Lit search: maintain humidity at 100%---I sealed the tub w/ a piece of plastic over top. I tried it with a fogger (water nebulizer--$20 or so),
SETUP---This one is designed to hold (3) 10x20 full nursery trays. It is made of (2 or 3) 1" 4x8 reflective backing styrofoam insulation. The edges are held together & water-sealed with gorilla tape. The front is left open for easily access. The rack is made of 3/4" PVC, except the cross-bars which are 1/2" steel conduit, for strength. The front has a piece of clear plastic which folds up over the top, for access, then flips down over the front, held to sides with a small piece of gorilla tape on each side.
--Heat--It is powered by a grow mat under a 10x20 nursery tray, on a thermostat, which is hung to the outside of the box, with a remote wire sensor inside the box.
--Humidity--just the humidity from the grow mat heating the water in the tray.
FINDINGS--
--Heat Source--with the thermostat, it stayed at 74+/- 2.
--Humidity---It seemed to stay near 100% humidity without the mister, but there were a few times where I misted a little with a spray bottle, just to be safe.
--AirFlow--It could use a bit more air flow, & smelled just a bit, but I never saw any mold.
--Use---I ran several trays through, & could start/end at different times. With new seeds, the germination rate was near 100%, in a few days.
--CONCLUSIONS:
--Structure--The Styro kept it insulated well, so I'm assuming energy use was minimal. Tray height--If shelves were just 1/2" higher, the2nd shelf could accommodate the taller 4" cups, also. Overall, the design is not bad.
--Heat Source--grow mat under water tray worked well & is viable.
--Humidity--For simplicity, keep it the way it is & spray it once every 1-2 days.
--AirFlow--If you want to get more elaborate with automating the humidity, have a fogger above (maybe on top, or off to side of top tray), but make sure a fan is blowing it around well. Then you have to deal with what that would do to temp regulation, or get a water-resistant fan.
--Light--can be regulated by flipping styro door up/down, on its gorilla tape hinges.
which goes under water. The little white disc you see vibrates super-sonically, which pulverizes the water into mist/fog. The fog was cool & hung low.
--Air Circulation---I ran the tube from a very small aquarium air pump, which moved the air around a bit, but not much.
--Results--had 2 germinations at about 2 days---after that--nothing.
--FINDINGS
----Heat Source--It was on the floor of my office, so it didn't need that much heat. Also, I didn't have a thermostat on it, so it got up to 95 at one point. Later I looked up the ideal germination temp of Tomatoes (what was in Germ1) & it is about 74F.---OOPS. Generally, it stayed about 85 which is where I originally thought it should be for hot weather crops like tomatoes, but we had a warm morning with the sun coming in my window, so it heated up.
----Humidity---I found that the fog didn't disperse evenly, & actually made things too wet. The seeds are supposed to be moist, not drown.
---AirFlow--the little aquarium pump didn't move the air around much.
--CONCLUSIONS:
----Heat Source--Grow mat is enough, but needs to be controlled by a thermostat, which I bought for $35 A small aquarium heater might be enough for this small setup, & I think it has a pre-set thermostat, but I think it is set to keep the water at 80F, so there is no adjustability.
----Humidity--I think the mister was not totally necessary. If it is used, it needs to be on a timer, so it only runs a few minutes every few hours.
----AirFlow---The reason for airflow is to prevent mold. Maybe because the soil I was using was fairly sterile, but I didn't notice any mold. In a larger system, it could be useful if trying to use a mister, but would require a larger air pump. The pump would be pulling air from the outside since they are not submersible, which would affect the temp. Ideal would be to have one which pumps air from within the chamber, but that would require a water-resistant pump--(much more expensive?)
--My seeds were bad, I boiled them, & basically killed them.
--Usage--worked quite nicely. Being able to do 3 full trays at a time is nice, including making it so I can start large seed - transplant-sensitive plants right into 4" pots & still be able to do 18 at a time. Rack height could be increased, but not by much, without interfering with the cost-effective use of styro board.
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