It’s a good thing that my hobby is neatly divided into seasons. It gives me time to forget how foolish I was to buy and save all those seeds last year, and how hard pressed I was to find warm places to germinate them. My wife Lisa (who I may have mentioned having the patience of a saint) tolerated it when my seedling trays migrated into the house, but drew the line after all the appropriate windowsills and nearby table tops reached capacity.
At some point those early-season seedling trays need to migrate out the greenhouse – not only for the sake of my marriage, but also because the plants benefit from the better lighting conditions of the greenhouses. I won’t confess here which was my greater motivation.
The difficulty: at the time when I’m starting many of my seeds (February, March) weather conditions can still be quite variable, and if I put newly sprouted seedlings out on an unheated bench, a bitterly cold night could knock them right down.
All of this explanation is by way of justifying another heated greenhouse bench. Here’s the video of us building it:
I won’t spend a lot of time recapping what I already said in the video, but I will say this: root heating has an incredibly beneficial effect of young plants. It increases root development in those vital early weeks, which in turn means a quicker, healthier plant. The nursery I work for uses a much larger an more robust boiler system with microtubes to distribute heated water to all the benches – and the results are phenomenal: big healthy plugs that are ready to transplant and finish in a larger pot within weeks.
I can’t duplicate that entirely, but I do get good results on these inexpensive benches. Because of the insulation, and because all the heat is released relatively close to the roots, they actually don’t take much electricity to get a good result. Later in the season, I use the same benches for rooting my semi-hardwood rose cuttings.