[Hippocrates_Garden]

Go for it. Why not? Or even in a bed set aside for surprises!

[Hippocrates_Garden]

My kneejerk thought is “why do you need to heat the entire greenhouse, air and all?” depending on what you are trying to do, there may be another way to approach this.

If trying to keep things alive to have winter harvests, and depending on where you are, It may be more efficent to have those crops, which I’m going to assume will be leafy greens) already grown when winter hits. Many of the plants don’t really “grow” during winter, but more or less hold on where they are, this being more a factor of sun hours (and possibly intensity) than temp. For this, Elliot Coleman technique of one or more floating row covers might do the trick.

However if wishing to heat the greenhouse for starting seeds etc earlier, the main concern is potting mix / root temp. For this just use the compost pile as a hotbed, on which you place the seed starting trays, possibly with an extra floating row cover if needed. Thus you’re only heating their feet (just like radiant in-floor heating) rather than focusing on heating the entire air mass of the space. Of course, it may knock a degree or two off the cold, but won’t need to generate near the BTU’s to do that and get the same result.

Of course, if you have raised beds and enough material, and don’t mind emptying them, then refilling, you could put the N rich stuff at the bottom or middle of the entirety of the entire bed, and let it bottom heat everything.

that’s just immediate musings. Oh, and get Elliot Colemans 4 season garden book, lots of good info on this stuff in there.

[Hippocrates_Garden]

I’ve not done muscadines, but like Darren said, should be same as grapes.

When training grapes on to wire, I can’t remember the source, but seem to remember some types grow essentially “up” and some grow “down”, as in from the branch as it were, the suckers go more up or hang down from the start.

When trellising, if you notice a significant predisposition, this can determine where to pur your wires, as if they grow “down”, put the wires higher so as they droop, you can harvest, prune, manage etc. Whereas if they grow “up”, have the wires lower to keep everything in reach. (but who knows, that may have been a strange dream). Just something that came to mind.

[Hippocrates_Garden]

You may be talking about “Climate Batteries” kind of Geothermal for greenhouses, based on air rather than liquid as the thermal transfer medium.