Can hugelkultur shift my effective hardiness zone?

Hi All, just joined permies, completely new to all these concepts (found Paul about a week ago) but fascinated by them.

I'm in zone 7a in coastal NJ, I'd love to be able to grow avocados here, but even the hardiest are out of my zone. Is it possible that the heat of biomass in a composting hugelkultur could shift my effective zone? Is there a way to quantify based on bed size/volume, what zone becomes accessible?
It seems that this is exactly what Sepp has done, but in a more "throw it in and see if it'll grow" type manner.

Thanks (and greetings!)

-Marc

The one HUGE advantage Sepp has is all that snow. His soil temps are moderated by all that insulation that we just don't get with the bare cold.

If you can come up with a viable alternative to insulate the ground you have a chance. This can be done with deep mulching, but it gets financially challenging for more than a couple trees.

With hugelkultur you should not be expecting a hot composting reaction. It's going to be a fungal decomposition, not a bacterial one, so should not expect heat from the process. Where it can impact your microclimate is more along the lines of insolation of the bed.

Position your hugel bed so it has a south facing slope with good sun exposure and you should be able to get it significantly warmer than a flat bed in the same location. Add a pond (or other reflective body) south of the bed and the reflected sunlight will add to the effect.

Peter Ellis wrote:Position your hugel bed so it has a south facing slope with good sun exposure and you should be able to get it significantly warmer than a flat bed in the same location. Add a pond (or other reflective body) south of the bed and the reflected sunlight will add to the effect.

OK, I don't have the land for a pond, it's really just going to be a conventional 20'x30' garden converted to a hugel bed(s). I've got fallen maple starting to rot on my property, so it seems like a no-brainer. The short edge of the garden is southern facing, so I'm thinking I'll make a few 20'-ish wide mounds with south facing slopes. The garden is fenced to keep the rabbits and gophers out - the 'dept. of making you sad' in my town won't allow the type animals that might keep them in check, and my son is allergic to dogs.

Would rocks on the southern edge of these help retain heat? There is a huge oak on my neighbors property to the east that shades out the morning sun during cold weather months, so maybe some tiles on the eastern part of the fence would retain some heat.

If you've got any ideas around gopher/rabbit management that might allow me to grow outside the fence, please let me know.

Thanks!

-Marc

Short answer, unfortunately, is no way. Avocados are very tender plants, with very shallow root systems. There are 'hardy' varieties that can tolerate some light frost for short periods of time, but not sustained freezing temps like you would have during a cold spell. I would love to be proven wrong, but I do not think there is any chance of success with avocados in your climate, regardless of what microclimate manipulation you might try.

I have a few seedlings of avocado outdoors now, and with two days of freezing temps (-8ºC low to 0C high), and the avocado plants survived when brought indoors.

They were in sheltered spots near the walls of my house. In an exposed place, they have died, of course.

You could have a tree growing with a cold frame over it, that would be the ONLY way possible (that might work), otherwise it would be not possible.
Or plant it in a large pot and bring it back indoors or preferably to a cool but not freezing shelter, for the winter.

It may be possible with some serious micro-climate manipulation. I would start with a hugelkulture shaped into a sun trap or even a terraced high bed as well as some trees to increase the effect and reflect heat into the target space. Crater gardens could also help especially if a body of water forms in the center and of course a nice deep mulch of 20+"