I will be planting mammoth sunflowers this year for multiple reasons:
* seeds for birds/chickens (maybe even me?)
* attractive to pollinators
* deep root system to help open up compact soil
* trellis beans up
* deep roots can also mine deep nutrients for use by other plants through leaf drop
Something that I have been mulling around in my mind is harvesting the stalks of these sunflowers at the end of the season and storing them until next year to use for structural components like one would use small to medium diameter bamboo for. I have heard that mammoth sunflowers often have to be cut down with a saw-z-all due to the thickness of their stalks. Has anyone harvested the stalks for future use before? If yes, what are your experiences? How long would they last? I am thinking that they should have several years longevity since they are quite robust. I am comparing these in my mind to corn stalks which stick around for quite some time and don't have quite the cross section/wall thickenss that I understand that these large sunflower stalks do.
"Turn your face to the sun and the shadows fall behind you." ~Maori Proverb
I haven't used mammoths, but my experience is they don't retain enough structural strength to do much past a year. While they don't completely decay, they do get brittle.
I bet if you weaved them green fish), they would hold up as a wattle fence for a few years (use coppiced wood for the stakes/veriticals).
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Jen, I grew mammoth sunflowers last year, and will again this year. It was my experience that the stalks broke easily when the plants were done. I would not expect that mine would even have served for doing tepees for beans.
Sounds like a use that is similar to pampas grass shoots. They are soft, brittle, barely make it through a winter, BUT...if you need something temporary it would be worth the effort to harvest it for that use. Or something inside. Or decoration (ie. not holding any weight).