Last week we learned about sowing seeds. We learned that an important part of this process is soil temperature. This week we will learn about the importance of bench heat.
In a typical greenhouse propagation there are often some benches that are heated. This heat assists germination, in the case of seeds, and rooting in the case of cuttings. The entire greenhouse does not have this system, because it is often expensive. Also once germinated or rooted, bench heating becomes less important. There are a few ways systems that are used commercially. Some will use hot water run under the bench through tubes, but more commonly it is an electric pad. Greenhouses use an electric pad that is the width of a typical flat but at least 10' long.
While gardeners can buy heat mats to propagate their crops there are other options. I use an old heated blanket; rope lights will work as well. I saw an elaborate home system that included making an elevated bed filled with damp sand. In the sand heating wires were placed. Sand transmits heat uniformly and creates a good place to place flats of seedlings.
A traditional method uses a modified cold frame. The cold frame is dug out, and filled with manure. As manure breaks down it releases heat and warms the surface above. When transplant are placed above this manure they are warmed, even after the sun goes down.