I want to qualify this question by giving some background:
-Long time gardener and have started my own seeds for 10+ years
-I am in Zone 6A in Michigan
-Previously started my seeds in my basement with multi-rack and lighting setup. Ambient temperatures can be controlled at 70 – 75 degrees
Now I have a new home without a basement and no space indoors to setup my multi-rack system. Moved last Summer so missed the growing season and this will be my first go at starting seeds in my new seed starting space in an unheated garage/polebarn.
Already purchased several heating mats to start my seeds but my concerns are ambient air temperatures once the seedlings start growing. Right now ambient temperatures are in the low 40s in the space, despite outside temps in the single digits (thanks to the building being dark color and facing south/southwest).
I am anticipating ambient air temps in the space in the 50's while seedlings grow. How would this impact the growth of the seedlings after I remove the heat mats?
The theory in my mind is that the seedlings may grow a bit slower but they would also be better prepared for placement in the garden? Here in MI even well after the plant in date the outdoor nightime temps can be in the 50's/low 60's. Would this benefit me in the long run as there would be less chance for the plants to stall as they are more used to the 50-60 degree temps vs. hardening off and planting plants that were grown in consistent temps in the 70's in a heated house?
Lastly I could use insulated blankets to enclose the growing racks, which will keep the heat given off from the grow light system from being lost into the room, and creat a warmer microclimate. I would like to hear if others have done something similar?
Would love some opinions on how the ambient temps will impact my plants, and any tips and advice to help, short of heating the entire garage/barn?
by thesnowmaniv
5 Comments
In most indoor situations…soil temperature is more important, in my experience, than ambient air temperature. You will definitely need to monitor your soil temperature, though. If your soil is staying warm enough (70°+)…and your ambient air temperature remains 50° or above…you should be fine. Make sure your water is also around the soil temperature, as well.
I think cold tolerant plants will be fine. Heat loving plants will slow but as long as we’re talking about temps in the 50s should be OK. 40s will be an issue for things like tomatoes etc.
What I’d consider is getting a grow tent that will fit the entire thing inside and has a fan setup to keep air from getting stagnant and humid. Something like [https://vivosun.com/vivosun-mylar-hydroponic-pro-grow-tent-2×2-for-indoor-plant-growing-24x24x48-p148350832863748091-v148396918936661479](https://vivosun.com/vivosun-mylar-hydroponic-pro-grow-tent-2×2-for-indoor-plant-growing-24x24x48-p148350832863748091-v148396918936661479) but probably a different size (I don’t have the Vivosun, but was looking at it over winter just in case)
>>>”Lastly I could use insulated blankets to enclose the growing racks, which will keep the heat given off from the grow light system from being lost into the room, and creat a warmer microclimate.”
I start lots of my seeds in an unheated storage room behind the garage. Ambient temp is in the 50’s and 60’s most of the time. I actually think this is better for the seedlings. They grow slower, but with thicker stems and less tendency to become prematurely tall.
About retaining heat in the seedling rack itself, I use sheets of mylar that I’ve cut to size and stapled to pieces of cardboard. These have the added benefit of reflecting light. I like the way they “bounce” light into the sides of the seedlings.
[Mylar sheet](https://www.amazon.com/TEXALAN-0-25mm-Diamond-Highly-Reflective/dp/B08DSC149G?ref_=pd_basp_d_rpt_ba_s_1_pr_t)
Consider buying some sheets of foam insulation board with the silver face material. Build a box that would enclose your rack and lights. Reflective side on the inside. It will also help reflect light for the plants and insulate to keep the warmth in.
This is exactly how we start all of our first set!
We have a little table sitting next to it with a good quality power strip for the lights and the heat mats.
We have heavy-duty cardboard around where the electricity is, and we have cutouts to make sure nothing touches the power cords.
We have one fan going, so there is circulation to avoid damp-off.
We use clips to hold up newspaper as needed for heat-retention.
It’s a pain to lower & raise the lights all the time, so I have taken to raising sections of the heat mats instead.
Have fun!
A from Laurel’s Heirloom Tomato Plants