Viable, yes. But with some considerations. First, your 60+ degrees is great for growing the plants AFTER they germinate. Temps are only a concern for germination and then it is soil temp, not air temp that is important. After germination air temps are vital and 60-65 is considered the ideal. Much hotter results in leggy growth, stressed plants, and potential fungus problems.

Second, with direct sun on it the enclosed plastic space will "trap" heat and can get way too hot quickly so it will need to be monitored closely and vented/opened as needed. It would be better to provide supplemental lighting rather than the direct sunlight. The spectrum, intensity, and # of hours of exposure are all so low this time of year that about all it provides is heat. Using supplemental fluorescent lighting makes temp control much easier.

Third, using a source of bottom heat on your seedlings assures quicker germination. Light isn't needed to germinate, just soil heat, unless you are growing one of the few flowers that need light.

Dave

I've had the same scheme in mind, but now I see the need for supplemental light. My area - which is not yet put into play - are corner windows, 2 to the south and 2 to the west on the 2nd floor, which I thought ideal.

My plan included mirrors behind and under the pots to reflect the light from all angle, and I thought would be sufficient - but we've had no real sun at all for 5 days straight, and I realize, that some supplemental would be needed in such a time.

I just started a tray of different veggies. I use a propagation tray 32 coco pots a humidity dome and a hydro farm seedling mat. They're in a closet under a 4x48" t5 flourescent light . It took only a week for all my seeds to pop . Except for habeneros they'll take longer. My seeds include ; better boy, Roma, cherry, and yellow tomatoes, zhuccuni, cucumber, green beans, orange bell peppers, and the habeneros. I like the dome because it traps warmth and the vents allow control over humidity . I've always had success with this method. I think even in a window the light would be sufficient for starting the seeds. The mat produces the needed heat for fast germination and root growth.

Isn't 60-65 a little cool? All my pepper and tomato plants have purPle stems due to cold soil. Any advice?

lay them over on the soil - looks like you have room - and bury all that naked stem under several inches of soil. Just leave the tops above grounds and move your cages over. Water them in well. Give then a week then feed them well.

No because the goal at this stage is root development not top growth. Warmer air temps not only encourages leggy top growth and the development of molds and fungi, but also increases the demands for watering which slows root development. Phosphorus uptake to the stems and leaves is slowed by the cooler temps because it is used by the roots where it is needed.

If you feel the purpling is too severe then your plants may need a mild feeding depending on what growing medium you are using and the size of the containers the plants are in. Young small seedlings in too large a container are more prone to retarded phos uptake and seedlings that are in too small a container so are rootbound will also show signs of poor nutrient uptake. In other words, it is a balancing act so don't just assume it is due to cooler soil temps.

Dave

Isn't 60-65 a little cool? All my pepper and tomato plants have purPle stems due to cold soil. Any advice?

Sorry for the misquote above. This is the question I was addressing.

Dave

Crystal clear. Thanks Dave!