Best time for pruning/thinning culms?

[Matt in TN]

I know it's heresy, but I'm thinking about thinning out some of my Rubro to give more space between the culms and hopefully encourage it to spread out a little more. In my inexperienced head, it makes sense to leave everything at full growth all summer to help maximize rhizome growth, then thin when the bamboo goes dormant (maybe December?). Maybe by December I'll have lost my nerve, but I'm at least thinking about it at this point

Any tips/ideas on thinning to encourage better spread? Am I wasting my time and stunting the growth?

[stevelau1911]

I think it would make sense to thin the shoots as they are just rising so that all the energy gets directed towards fewer shoots which will make them taller and fuller. As far as existing culms, I would think that thinning out older culms once the new ones leaf out would be an ideal time since this is when the culms are depleted of energy and the new larger culms will have plenty of time to absorb energy through the year. Just make sure no more than 1/3 of the culms are thinned out so the plant can continue to increase it's energy.

If you cut out culms during fall, the rhizomes created by that culm won't have the energy source to support them and its when the culm stores up a lot of energy.

As far as spread, I'm still unable to get my juvenile moso to run, but I think mixing in something like horse manure into the first 6 inches of soil in a ring around the plant might encourage it to grow into that, and mulching it to keep the soil warmer and loose. Don't forget about watering that area too. You should have a much easier time to get your bamboos to run than me considering you have overall warmer soil temperature throughout the year.

[Markj]

it makes sense to leave everything at full growth all summer to help maximize rhizome growth, then thin when the bamboo goes dormant (maybe December?).

Perfect timing IMHO, get rid of all the old and small stuff and try and get a good shape going while you're at it

And recycle the trimmings back - If you need some new bean sticks, go and buy some the cuttings gota go back

If you cut out culms during fall, the rhizomes created by that culm won't have the energy source to support them and its when the culm stores up a lot of energy.

Steve- where are you getting this info from It's just wrong...

[Steve in France]

What I do if I feel I must trim out stuff is wait until this years growth has leafed out, look at what old small growth is shaded and take that out first. If there are small growth culms or whipshoots on the outer edge of the grove then these make good divisions and if taken now will have plenty of time to root up and grow in a pot. Once in a while I'll take a culm down from the center of the grove if it seriously improves the look of the whole grove. Standing back and taking a long hard look at the project will help to make the right choices. The object I feel is to create a more open grove that will get the maximum amount of Sun to each blade and at the same time both look natural and impressive. If a Bamboo is in a spot that is a little out of the way then I don't trim .
On another front ,I've moved up to Miracle grow twice a week now plus three month Osmocote every month, plus daily water. No trimming this year. Parvifolia looks a little bit of a mess but I'm keeping every blade for next years growth.
I'm not saying my way is the best , it's just the best wat I've worked out for my Bamboo and growing conditions.
For you in Tn your growing conditions will be better than mine if all is equal ie: soil ,mulch, fert and water. The extra heat and longer season means you can get away with more experiments because the Bamboo will grow faster and size up faster.
David says his Parvifolia is growing like a mad thing and he has little trouble with propagation from it. Parvifolia in more Northerly conditions seems to be harder to propagate from and slower to size up. I think your best bet is to be very agressive with the feeding and watering all through the season and from August on add more fert for Flowers and Veg as this will help with rhizome developement for next year. Pile on as much leaf mold as you can get in the Fall, I'm going for 8 inchs to a foot thick this year. If it has not rotted down by the Spring I'll rake it to loosen it up , add manure and lawn fert and speed up the process of decay. Always have a plan
Best of Luck with your Season
Steve

[David]

I thin after the culms have hardened and the branches are leafed out. If you take the smaller growth that is now shaded somewhat by the new growth I don't think you will effect the energy stores of the plant. I thinned a small grove of spectabilis last year taking perhaps 40% of the culms. This year it was one of the few bamboo that actually sized up. It needs thinning again!

I was recently searching for a small division of dulcis to send to a friend, and just began whacking away at unsightly culms. I don't know what impact that might have on next years growth, but it certainly improved the looks of the grove this year. I grow bamboo because I like the impact that it has on the landscape, so liking how the grove looks is important to me. If this means cutting and thinning then I'm going to do it. The exception would be a very young grove that needs all the energy it can muster just to get going.

I agree with all that Steve in France wrote with the exception of the use of mulch. We have so many moles and voles that thick mulch is an invitation to stay and have rhizomes for supper! I may use a very thin mulch on new plantings just to hold water while the plant catches on. Rocks or pebbles seem to be a good alternative at least for water retention, but I have not tried it.

Matt, I say stand back, look at it, and cut away what you don't like. Have fun! It's a plant not a religion

[stevelau1911]

I think I'll have to clear out 100% of last year's culms on my moso once these new shoots complete growing and leaf out. Some leaf buds actually survived, but from how they look, they can't provide that much energy. This grove should look beautiful again in another month.

[Tarzanus]

Nice new shoots, considering devastation that can be seen everywhere around them!
Looks like lower parts of older culms are still alive, if you keep them, you'll get thick layer of branches just above the ground. I don't think that will help the plant much. I would keep culms that are at least 1 or 2 feet high or have some leafs left from last year. I'd also leave culms that have no new shoots around them - you can always cut them off later.

[stevelau1911]

There are only about 60 shoots total so I'll leave it alone, see what it does. The biggest ones are around the 0.75inch mark while the smallest ones can be a hair under 0.5, and depending on how warm it is, most of them will probably fall in the 5-8ft range, and easily pass up the dead culms from last year. Even though the grove looks pretty destroyed, I think it still stores some energy reserves in the old culms even if they are top-killed above the snow line.

Once the new culms are hardened off, and the old stuff looks like it won't serve a purpose anymore, I'll get rid of them, maybe by July or so. Only the lower leaf buds made it through the winter so they'll be shaded out pretty well.

Here's how big the biggest ones are. There are around a dozen around this size, and they all seem to be coming up on the same side of the grove.

[RazinCane]

For what it's worth I prune the beginning of March taking out 3 yr. old growth, the logic being the resources needed to sustain the older growth is redirected into the soon to arrive new shoots and providing me with garden stakes for the coming garden season.