Hi Al -

Thank you for the information. At the moment I sat the plants directly on the mat but it doesn't seems to be warming them to any extent. I assume the heat generated by the mat is being dissipated to the ambient air more quickly than being able to heat the plant - thus the sand idea. If possible and you have time could you call me to discuss or perhaps I can call you -- I believe I still have your number from when you helped me a few years ago, I have had the heat mat on for 16 hours straight and haven't noticed any temperature change - even in the plastic saucers to catch excess water, The plastic saucers were in direct contact with the heating mat. Thanks! Brian

I would think that bonsai pots, because they are on legs with an air space between the mat and the pot, wouldn't heat up much, but pots with bottoms fully in contact with the mat should. Is the mat working? I guess you could try covering the mat with sand, which might tend to even out the heat a little, but I can't envision how it would INCREASE the amount of heat that made it from source to soil mass.

You can call if you like, but I'm not sure what additional help I'd be able to provide - unless you have other questions.

Al

Hi Al -

The mat is definitely working....I can feel that it is warm after being on for a while. the black nursery pots are not in direct contact themselves with the mat. It is the plastic saucer that catches any excess water that is in direct contact with the mat while the pots are inside the plastic. The plastic saucers are those very thin ones like you get at lower/home depot. As far as the sand idea I was thinking the sand that is below the surface will retain more heat that can be transferred to the submerged nursery pot. The sand at the air/sand interface I would expect to also lose heat to the air in the basement, The warmer sand below the surface is what I am hoping will transfer heat to the nursery pots. What i your set up for warming the root zone of your pots?

Have a great day!

Thanks! Brian

What is your mat sitting *on*?

Many overlook what they place the heatmat onto, such as a cold floor or a metal shelf... that might easily sink all the heat away.

My heatmat sits on an insulated surface like sheet styrofoam, a thick wad of newspaper, cardboard tray (wrapped inside a plastic trashbag to waterproof it), an upturned plastic tray...

id rather not let the mat ever get wet so it's wrapped in plastic, plastic tray/bucket sits on top and plant pot goes in that... it gets noticeably warm even without much heat conduction

i run it on a timer to control heat output

My homemade heated surface is waterproof so I never worry about it being wet. I have tested many times the soil temp of my nursery pots sitting directly on the heated surface and have always found the two temps to be the same. The surface is aluminum and the plastic pots are in direct contact.

Thanks Al C and Tamiya -

Tamiya - The heat mat is on a plastic surface. I will try the insulation you discuss. Thanks and happy new year to all!