I planted some arundo donax last year, and it was about five feet tall before my dogs chewed it up. I built a fence around it, and it’s starting to sprout back up. I’ve got a question for Joseph or anyone else who has grown their own: about how long does it take for a stalk to dry sufficiently after you’ve cut it off?
Thanks
Oh, Oh. I was going to ask that same question.
I have some growing near my house and I have been intending to cut some the last few weeks.
From what I’ve read, the stalks have to grow to lengths of 15-20 feet to acheive diameters of 1" That’s a few years growth in perfect conditions, then you’ll need 3+ years of air drying after the harvest. I did hear of one guy who keeps pieces in his attic to accelerate the drying process.
You would probably want them to get a bit larger than 1" diameter, as they will probably shrink a bit through drying. Cut them in winter when they are driest. You want to end up with 25mm external diameter when dry for concert D reeds, 20mm for flats. Then three to four years air drying, depending on the softness of the cane (determined by your local growing conditions). David Daye tried growing his own cane, but it appears that he has pulled that page from his web site.
djm
At least 2 1/2 to 3 years. The drying or curing process has to be allowed to take place as there are important chemical changes that the cane will undergo during this time. Accelerating this process may result in cane that is too hard or otherise unsuitable for reed making.
… and I nearly forgot, you want to wait until the sap has dropped before you cut it, otherwise you may not get a good result from drying. Cutting real late in the winter, spring or early summer is a good time to do this.
Ideally, you really want to look for the stuff that has been dead a good while, stuff that hasn’t any green leaves on it unlike the photo above. Even then, it will need to dry a little longer… up to a year perhaps.
It appears in your last photo that the sap hasn’t dropped yet. 
djm
… nothing gets past you, my good fellow, 