Overwintering Bamboo in Containers

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Kippy
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Overwintering Bamboo in Containers

Post by Kippy »

I know it may seem like odd timing, considering that I am misting my bamboo plants two times a day in the midst of a heat wave, but I have some questions about overwintering bamboo in containers. First, let me say that I know it is risky business, and no matter what steps I take, there is a definite probability that my bamboo will not come out of winter unscathed, or even alive for that matter.

I built two containers that are each six feet long, two and a half feet high, and one foot wide. They are placed side-by-side on my patio, so it is effectively one large twelve foot long, two and a half foot high, one foot wide container. In each container, I have two phyllostachys aureosulcata 'spectabilis' plants, for a total of four plants. The plants each have three to four culms, which are five to seven feet tall. I live in zone 6a, my patio gets full sun, and it is not sheltered from the westerly winds. Each planter is about one-hundred pounds, and each is filled with about three-hundred pounds of soil, so they are not easily moved.

Since they are rectangular, and based on feedback on another bamboo forum, I have been looking at foam board/sheathing insulation. The boards are fairly inexpensive, and they have what I would consider to be high R-values. For example, Home Depot sells 4 foot by 8 foot generic brand boards that have a R-value of 5.9 for $10. Will this be sufficient to keep the root mass from freezing in zone 6a?

If this is not sufficient, additional layers of the foam board could be added, or other products could be layered on, such as radiant barrier insulation (think: tin foil). Are there any other materials that I should be considering? I have seem people mention asphalt roofing shingles, but then I see others say to avoid warm up/cool down cycles.

When one uses bags of leaves as an insulating material, do they act solely as insulation, or does the decomposition of the leaves add heat to the equation? Or, at low temps in a sealed bag is decomp not a possibility?

I plan on bending down my bamboo culms, staking them, adding mulch to cover the culms as best I can within the confines of the planter, and then covering the tops with some kind of tarp-like material to prevent wind damage. It still seems weird to me that this won't hurt them, but the alternative is them dying, since it is quite a windy location.

So, any advice or input that you can provide is much appreciated. I really love my bamboo, and I am hoping with the proper plan of action, I can continue to enjoy it.
ShmuBamboo
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Re: Overwintering Bamboo in Containers

Post by ShmuBamboo »

Well, I live in zone 7 or 8, depending on the year. This year's low was 22 F, last year was 10 F.

I grow a lot of my boos in plastic pots, some as large as 40 gallons with 15 ft. culms. I sink them in the ground and cover them with mulch/wood chips/leaves to keep the rhizomes warm in winter and cool in summer. Boos in pots are a problem in colder climate becasue the rhizomes are exposed to cold temps. R value for pots is pretty useless, unless you are heating the inside of the pots. There is not enough heat in that much soil to retain heat for very long, and after a day or two of freezing temps the soil is going to be freezing inside the pots as well. By sinking my bamboo pots on the soil, I am getting heat from the ground, which is replaced as it is lost to the potted boos. If they are above ground they do not have a heat source, and so they are apt to freeze. It is similar in summer, above ground they bake in high temps, whereas in the ground they are protected from the heat by the surrounding soil.

So if you are wanting to keep your boos alive there in winter in that kind of planter, I would advise that you use a heating device in the soil to keep them from freezing. Use resistance wire sold at some nursery supply houses for that purpose. They also sell that for heating pipes in winter months. You can also buy pads that heat the underside of tables that plant pots are set on in greenhouses. The Russians figured out some time ago that it is better to heat the soil and/or pots wit radiant heat than it is to heat the air around plants in winter. Heating the air is not as efficient or as effective. That does not keep your boos from cooking in the summer, but watering will help cool them. The farther off the ground or deck, generally the more they are apt to cook (as well as freeze).
Happy trails...
Kippy
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Re: Overwintering Bamboo in Containers

Post by Kippy »

Thanks for the reply, Shmu!

The more I thought about it, the more I felt that I was missing a part of the equation -- heat. While heat tape looks like an interesting product, I think that it might go beyond the scope of what I feel comfortable doing.

I think that I might revert back to my original plan, which was to haul the planters into the unheated integral garage. I had abandoned the idea due to the fact that a.) the planters are unwieldily, weighing far more than I imagined they would, and b.) the culms of the bamboo plants I purchased are way taller than I was expecting, over seven feet tall, which when added to the planter height is an overall height of over nine and a half feet.

However, since keeping them warm enough in their current spot to prevent freezing is going to take extreme effort, I might as well put that extreme effort into a one-time event, like moving the planters into the garage. The cost of the materials needed to heat and insulate the planters in their current position would likely exceed the cost of a heavy duty hand truck.

Since I was planning on bending the culms over and tarping them, I can just bend the culms over to allow them the necessary clearance to fit into the garage. I could see the task of bending the culms over getting difficult after a few seasons of growth, but topping would be another option.

I had great success overwintering several tropical plants in my garage last winter, so hopefully, I can succeed with bamboo.
stevelau1911
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Re: Overwintering Bamboo in Containers

Post by stevelau1911 »

I believe that tipping over any container and tarping the bamboos should be enough to protect them over the winter as long as it is zone 6 or warmer. It has worked very reliably for me with every bamboo except for tropical bamboos which still survived, but were damaged.

Here's a 2 year old post on overwinter bamboo in containers.
http://www.bambooweb.info/bb/viewtopic.php?f=4&t=4789
bronze4art
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Re: Overwintering Bamboo in Containers

Post by bronze4art »

Hi:

I am no expert, but if it were me I see two choices 1, Foster in greenhouse.
2. Gently pull plants from container, shake off dirt and put in a trench or holes in ground.
plant a little bit deeper and leave concave area around plants, use huge amounts of mulch (leaves, grass clippings, etc., concave mulch pile also) fluffier stuff on top, mix as necessary while first mulching, water from time to time. If you have to get aggressive to pull plants apart ok, use a Sawsall or loppers if necessary. Better than having them freeze and die. Here in Southeast Michigan bamboos in ground do just fine. Containers very difficult for bamboo over winter. Most other evergreens in larger containers (maybe 7 gal.on up depending) do just fine. For bamboo in containers I think repeated freezing, thawing and drying-out is part of the problem. For your containers: Massive amount of mulch or leaves might work. In or out of the ground next to a house foundation and out of the wind will help. I plan on putting several smaller plants half in the ground next to the house under faucet this year, and I might leave a couple in containers. Dirt from hole around the edges and huge amount of leaves. I am not sure but I think some freezing is okay. A repeated freeze and thaw might be bad. I think some bonsi guy said "Let my evergreens freeze, then pack them in leaves". But bamboo in containers has always been difficult. Some winters are very bad; some winters aren't so bad.
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Re: Overwintering Bamboo in Containers

Post by stevelau1911 »

This winter, I am putting all my potted bamboos in my solar greenhouse so they can get some light through the coldest months.

It seems like potted bamboos are pretty easy to overwinter even without a greenhouse since creating a tarp bed is pretty much the same as burying them underground with less work. A 20ft by30ft tarp only costs about $40. Even in ground bamboos can be protected the same way as long as they are still flexible enough to tie down with a tent stake. The layer of snow over the tarp is usually enough to keep the pots from freezing over even when it dips below 0F.


I'm hoping that we will see a little bit of sub zero this winter because I want to see how well the greenhouse holds up, and I really don't know the hardiness of my bamboos anymore since they have matured a lot since 2010. My guess is that the hardier ones will still be mostly green after a night of -5F. They are still perhaps 15 or more years from reaching their full size and hardiness potential, but most of my groves don't look completely juvenile anymore.
bronze4art
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Re: Overwintering Bamboo in Containers

Post by bronze4art »

I agree light over winter is important. I have Sasa seedlings in the ground, I am not sure what is best to do for winter.(I posted a question under "seedling questions" and hope it is okay to say so here). Only once, in many years did a plant, in the ground loose its leaves over winter(plant recovered very well sprouted leaves). My garage is detached from house and will freeze solid here. I am very good at digging plants of all sizes and like to see others get them. Otherwise need to learn and experiment more.
Alan_L
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Re: Overwintering Bamboo in Containers

Post by Alan_L »

Light over winter is not important, as long as the plants are dormant or semi-dormant.

I've kept bamboos in an unheated garage with very little light and they've done fine. I've also laid potted bamboos on the ground and tarped over them and they did fine too.

Snow cover is good for your seedlings -- it will protect them from the coldest temps and wind.
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needmore
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Re: Overwintering Bamboo in Containers

Post by needmore »

Spent 2-3 years massing/tarping bamboo outside in clear plastic, leaves held fine in fact new ones had initiated but those bamboo never seemed to shoot properly to me and they ended up being tossed so I quit that practice. Klyn Nursery on Lake Erie tarps their bamboo and they do fine, I was told that using clear plastic was my error but I can't relate that to compromised shoot buds, the variable that leaves for me is our minimal snow cover most winters lets the cold do more damage. We get snow but big snows are rare and generally they don't last all that long so the pots are frequently uncovered during cold snaps.
Brad Salmon, zone 12B Kea'au, HI
http://www.needmorebamboo.com
Alan_L
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Re: Overwintering Bamboo in Containers

Post by Alan_L »

Good point Brad -- I never really monitored the shoot production of the plants that spent the winter tarped. I know I've never been overly excited about the shoots that those plants produced the following spring, but I attributed it to being in the pots too long, not getting enough water/fertilizer the previous year, or other factors. Probably a combination of all of them.

I've already decided not to do this again this year, mainly for the amount of work required and the ugly factor.
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Re: Overwintering Bamboo in Containers

Post by johnw »

Brad - By tarps I assume you mean that material that feed bags are made of, woven plastic and opaque. All plastic sheeting used for winter protection up here in the north is white and UV protected, it reduces temp fluctuations and wind burn on plants in coldframes large & small.

When bamboos are tarped are the pots sunk into the ground, partially sunk or not sunk at all? I'd guess there must be considerable root and rhizome bud damage if they are not completely sunk and might that not explain their poor performance the following year? While we get lots of snow it hardly ever stays around too long and we never seem to get enough when it's really cold.

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ShmuBamboo
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Re: Overwintering Bamboo in Containers

Post by ShmuBamboo »

I have never had issues with boos needing light here in winter. They completely ignored my moving them into the insulated/unheated garage here last year. I will do the same again this year.

As for pulling boos from plastic pots in winter, that seems like a bad idea to me, for many reasons. Pulling them from the pots can damage the rhizomes. Putting them in the ground in fall/winter here will allow them to freely run and establish rhizomes in the ground. My rhizomes typically run the most in the late summer through early winter here. Also putting them in the ground here directly exposes them to voles, and voles do the most damage here eating rhizomes in the winter. It would just create a vole buffet. Every potted boo that I have sunk into the ground here has multiple vole tunnels up to the plastic pots. Which may actually have benefits when it comes to drainage.

I have never had issues with over-wintering my boos in plastic pots. If you want more insulation, re-pot them up now and the added dirt will help insulate the rhizomes. If you bury them in the ground as I do here (and have for about 8 years now), I do not see how the plastic is doing anything, other than protecting them. I do not grow many types of boos that do not tolerate the cold temps here, so I do not do anything other than sink the plastic pots into the ground leaving about a 2 inch lip and covering that with wood chips. The culms are exposed year round. Actually, this year I have come to the conclusion that my potted boos generally do better than the ones planted in the ground. Mainly because of vole damage, but also for better water retention in summer months.

As for water damage and over-watering in winter months (or even summer months), I got 12 inches of rain in June here and I had no rotted boos. I got 13 inches of rain this October and I also have no rotted boos. At my ex's sheep ranch south of Eugene, they got between 8 and 12 feet of rain a year. I have found that they are impervious to any amount of water as long as the soil in and around the pots has good drainage and they are not left in standing water. I use about 50 percent organics in my potting soil, and I have silty loam soil that drains well here. I only lose boos here to 1) cold and 2) voles. I have also lost culms to snow loading and to high winds. Vivax is notorious for not doing well with snow becasue of its thin culm walls, and I lost some tall Bory culms this year in a wind storm in the spring.
Happy trails...
stevelau1911
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Re: Overwintering Bamboo in Containers

Post by stevelau1911 »

I only meant that keeping potted bamboos inside a greenhouse where temperatures stay warmer, and get exposed to the sun through the winter may help the growth a little bit. By around December, temperatures inside my greenhouse should still get cold enough for proper vernalization to mature the shoot buds for next year.

They still overwinter no problem under dark tarps. The need for sunlight and photosynthesis seems to shut down when the temperature drops to a certain level. It might be around 40F or maybe even lower, but I don't think there can be very much photosynthesis when the temperature is below freezing.
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Re: Overwintering Bamboo in Containers

Post by Tarzanus »

I've removed one of whip shots that emerged 3 or 4 months ago and since the Phyllostachys is growing in container, I took most of the rhizome with it. I've noticed fully developed white-yellow swollen buds all over the rhizome and large amount of feeding roots. Steve, does that mean it got rested enough to start growing again as it was spring? Does winter really activate rhizome/shoot buds?

I'm taking it inside, perhaps it survives, if not - no problem. :)
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Re: Overwintering Bamboo in Containers

Post by stevelau1911 »

Many bamboos should have swollen shoot buds at this time of the year, but that doesn't mean that they are ready to shoot because you probably haven't given them any exposure to temperatures in the 40-50F range for proper vernalization which can vary based on what kind of bamboo you have.

I've tried to get extra growth out of bamboos every winter testing various species, but it seems like the only thing I end up doing is setting them back as they fail to adjust to outdoor conditions even when they are set by a south facing window. It seems like they need a period of cool temperatures, or the natural decrease in daylight to trigger dormancy which is required for the explosive shooting season that we are all familiar with. Unless it is a very young moso seedling, bamboo divisions that are over-wintered indoors tend to sit there all summer doing nothing or dying off as they simply seem to lack the will to grow.

If you are in zone 7, you can probably get one of those cheap hobby greenhouses such as the one I have. There's probably no need for additional heating as long as you have a well insulated greenhouse with a few barrels of water inside. You can overwinter all kinds of plants in one of these greenhouses. They do increase the temperature by quite a bit for both day and night.
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