What is the easiest way to propagate P.nigra? I have heard that it is very difficult. Has anyone any tips?
It's no harder than any other running bamboo. You either need a division from an existing plant that includes a good sized root ball, or you need to start it from a piece of rhizome with viable buds. A division is the most reliable way; you may have anywhere from 0-100% success trying to start from rhizome pieces. You cannot propagate any running bamboo, including Ph. nigra, from branch or culm cuttings.
I've heard a good technique for propagating bamboo from escaped rhizomes that shoot out of the soil. Instead of re-burying the rhizome or cutting it, you direct it into a container - via a small hole cut in the bottom. A two or three gallon container should be perfect. Anyhow, you let the rhizome fill the container and produce a culm or two the following season - then you can sever the rhizome and either re-pot or else transplant the new division.
That method does work sometimes, though not always. One of the problems with that approach is that you cannot control the length of the rhizome. Sometimes a rhizome will extend, say, 10' before it decides to put up a culm, and that makes it difficult to contain in one pot!
Thank-you Kudzu9 and Greenman28 for the input. A friend told me that you could propagate it just as you would a grape cutting. I thought that was to good to be true, since the stuff is so darn expensive to buy!
the rhizomes that have poked out of the ground have all become culms...unless I bury them...and even then they tend to put up a wimpy culm from the area of the rhizome that is still above ground. Here's a pic of a rhizome that emerged horizontally. I trained this one upward with rocks and cordage, but it is very weak. If I were to do it again, I would send it straight through a hole in a bucket of potting mix, then I would let the rhizome shoot up out of the bucket to form its wimpy culm. Essentially, this would be like ground-layering a rhizome...but easier to control, and less shock when cutting it free.
Nature's devining rod...they always point toward water.
Ha! You're right!
It's funny, but I thought the rhizomes would drown in that "ditch," which stays wet for two months or so during the winter. However, as I was clearing the ditch the other day, I found a lacework of big rhizomes passing through....so these guys might tolerate more water than I'd thought. Of course, a really wet season might do them in...but there's plenty more above the water-line.
I think they can easily survive constant water, as long as some/most of the rhizomes are in normal dryer soil.
Putting the running shoot into and through a pot of soil is a great way to propagate new plants. No digging which saves time and your back.
I do that often with potted bamboos. I recently set a small pot beside a larger pot with S. tootsik 'Albostriata' growing in it. It put out a whipshoot through the bottom hole in the larger pot. I simple ran it through the smaller pot and filled it with soil. Now I have two S. tootsiks.