Overwintering outdoor bamboo until established?

[Snowbird]

I have chosen to take a chance on a few boos that are likely to have top kill in my zone. Additionally, I'd like to keep more leaves on my hardier boo to better facilitate next years growth. I was thinking of staking three wooden dowels on the ground to support some insulating material. Burlap, clear plastic or both have crossed my mind. I've heard that some people around here will wrap theirs with clear visqueen through the winter season. Though, I wonder i this would negatively affect the bamboo due to the lack of CO2 exchange.

I've searched the site and have been unsuccessful in locating previous threads on the subject but maybe there are some I've missed. If there are any links or tricks of the trade, I'd love to hear about them.

Thanks in advance,

Seth

[Mark Meckes]

Hi Seth,
As I begin to experience a serious meltdown here in Texas from a summer heat wave, it's a good time to cool off my mind by thinking about the winter season. :)

There are a lot of different ways you could go about protecting your bamboo from the cold.
Here's some things to consider ...

- Use a breathable wrapping, otherwise a buildup of moisture or trapping of too much heat on warm days could create other problems.
Another alternative solution is to make an initial cage out of chicken wire that may more may not need to be lined with a breathable fabric, though this will be another thing that may need to be stored during off season, unless for those that have bunnies or other critters going after young shoots.

- Insulating mulch should be airy. It's the air between the mulch that has the most insulating effect. Compacted wet mulch will freeze solid.
There are two purposes for mulch.
- Protecting the rhizomes
- Protecting leaves if the mulch is built up around the planting within in a cage.

A good example of an airy mulch is pine needles. Loblolly pine needles are sold in southern states as pine straw.
Shredded wood chips, straw and leaves mixed with branch clipping etc could also work as a ground cover
I used to rake up my "autumn leaf harvest" and put it around some of my bamboo when living in the north, to give added insulation.

One thing about applying winterizing mulch is not to do it too soon before the weather cools down.

Well, these are just some preliminary thoughts.
I look forward to hearing how others keep their outdoor plants snug over winter.

Mark

[Snowbird]

- Use a breathable wrapping, otherwise a buildup of moisture or trapping of too much heat on warm days could create other problems.
Another alternative solution is to make an initial cage out of chicken wire that may more may not need to be lined with a breathable fabric, though this will be another thing that may need to be stored during off season,
Mark

well that gives me an idea. I have been growing tomatoes that got huge this season, requiring more support than anticipated. the solution was a multitude of the newer cages that will of course have to be stored during the off season. well, that is unless there's a better use for them in the winter.:)

i'm thinking a fixed 12-16" of burlap at the bottom with mulch piled into it. Then a simple burlap bag over the top for the coldest days. its simple and easy to remove for the nice days.

i'd still love to hear what others in cold/cool climates are doing to grow those borderline not hardy enough boo.

thanks again,

-seth

[ShmuBamboo]

Well, there in Ootah you are apt to have really cold weather in winter. I have read some on this subject and there seems to be several 'levels of temperatures' of killing that happens as a result of boos being exposed to cold. The first temperature is that the leaves drop. Then the next is when the tops of the culms die off. Then when the whole culm dies off to the ground. Then finally the lowest tolerable temperature is when the rhizomes die off. Usually these events occur in progressively colder weather, though with some types of boos they all occur at similar temps (especially tropical bamboos; case in point with some bamboo I brought back from South Carolina that completely died at about 28 degrees). If you post the types that you have I may be able to find some numbers of the temperature gradients of survival.

Several ways that you can get around the cold to establish plantings. One is to pot them up for the first year or so in a large pot so that you can move them near the house or into a greenhouse or someplace warmer in winter months. I have 3 boos here that are marginal in this area. I have them in larger pots and they will be moved next to a sliding glass door here in winter. We have an outdoor wood boiler, so the house is always 70 degrees in winter months. Larger boos will be more robust than smaller ones, and after a year or two in a pot it might be large enough to survive a winter in the ground. Another technique is to put lots of mulch down on the ground to protect the rhizomes. Also you can fill empty plastic one gallon milk jugs with water and put them around the bamboos and swap them out with melted water ones if it freezes. When water freezes it gives off heat in the process. I keep water jugs around my orchids here in their greenhouse. If it gets really cold where you live this may not be realistic. Of course, buying a bamboo that is not cold hardy to your zone may not be realistic either :rolleyes: Or maybe you have to grow them as an annual?

Wrapping with material may help with things like wind chill, but if the bamboos are solitary that will not likely help much. If there is no source of heat, the heat will just leave them over time and all you are doing is slowing the cooling process. The result will be the same in the end. A dead plant. A source of heat like water bottles would be needed to protect your plants. If they are near the house then wrapping them may help, as the house would supply some heat in winter. The ground will also supply some heat as well, but if it freezes for some depth, the ground may not help supply much heat either.

[sasa fool]

Here are my thoughts on the subject:

In my experience, I have found that extra winter protection allows me to grow plants rated a zone warmer, but the reality is that some may survive but will not prosper. And I've tried many things to protect the culms - deep mulching of the rhizomes; covering them with blankets; burying them in snow, leaves, and mulch; spraying them with water; venting the dryer towards them. And to some extent all of these protection attempts (except the water) have helped. The problem is that as your groves expand it is no longer possible to protect more than a few culms. I still employ some of these methods by selecting culms of my prized varieties for 'wintering over' and I am having the most success with burying entire culms in mulch, blankets, snow etc. when the forecast first calls for subzero temperatures (for me this is usually late December or early January) and continuing to do this during extreme cold snaps, uncovering once it 'warms' back up to above +32F, in my experience it takes a long time before the leaves are damaged by the burying. My goal is to save a few culms of the species so that there can be active photosynthesis during the spring shooting period.

I have reached the conclusion that despite how excited I am at the prospect of planting a newly acquired species, the best strategy is to container grow the bamboo until it has really filled up a large pot with new rhizome growth. I am presently up-potting new plants until they are well established in squat 7-gallon pots before planting them out. I believe that this extra rhizome mass will help the plant to endure cold temperatures and also to have much greater energy for producing new canes in the spring, particularly if there is top kill. This means that one must over winter the bamboo indoors for at least 1 full growing season which may not be possible for everyone.

Winter Damage

Bamboo is damaged by extreme temperatures, cold dry winds, and prolonged periods of below freezing daytime highs. All of these conditions are even more damaging if they occur when the bamboo is exposed to direct winter sun as the sun light adds to the other environmental factors that desiccate the bamboo leaves. When the ground freezes the rhizomes can no longer take in water and they respond as they would in drought conditions - they curl up their leaves. If this condition continues for very long the leaves will ultimately dry up and fall off. As long as the leaf buds on the culm branches are undamaged, new leaves will appear in late spring.
Bamboo displays cold weather stress beginning with the leaves, which will start to show signs of cold-burn, starting at their tips and moving towards the culm, eventually drying out and falling off. This is known as leaf burn. Culm damage comes next and the culm will begin to die from the top down until total topkill occurs.
The most critical winter protection that you must provide your bamboo is to deeply mulch the rhizomes. Even if total topkill does occur, as long as you have deeply mulched the rhizome system, the plant should continue to live and produce new shoots in the spring, however, the ensuing culms will be smaller than the prior years’ growth because the energy reserves of the colony have been stressed. Another way to minimize winter damage – particularly if you have selected a marginally hardy variety – is to be aware of any microclimate protection that a planting site may offer. These sites would provide shelter from winter sun & winter winds, and may also offer a few degrees of radiant heat from a house or other structure – even your clothes dryer vent can provide some extra warmth on those subzero nights but care should be taken so that the vented air does not directly blow on the bamboo leaves.
In my location our coldest subzero temperatures usually occur as a result of snow covering the ground. The snow cover reflects daytime sunlight back into the atmosphere preventing the ground from receiving solar warmth and it also blocks the existent ground warmth from radiating back upward to the atmosphere. When these conditions are present, for additional protection I usually will bury my most sensitive bamboo in deep piles of snow. This will greatly help to protect the foliage from the air temperatures. I am always amazed to see how the shrub & ground cover species that were totally buried in snow, will emerge looking fresh and undamaged by even the coldest air temperatures. The worst situation is for the subzero spell to occur with no snow cover at all, followed by sunny days.

[Snowbird]

Thanks for all the responses. very good ideas for me to incorporate. the ones i am worried about are the zero to -5 bamboo. luckily, all but my fargesias and semiarundinarias are in the back yard and protected from winds by fences, retaining walls and a 30' high house wall. i planted far enough away from concrete as to not conduct cold to the roots. my front yard is less protected with two fargesia robustas in the park strip next to the road. i am worried about both the wind and possibility of plows throwing salt and snow on them. i have considered the possibility of potting those until next spring to give them a better chance. if that is the case, what size pot would work best for this 1 gal planting? will they continue to grow rhizomes over the winter or do they become dormant indoors as if they were outside?


shmu, here's my best guess at the temps for my boo from reading a few websites.

1. Phyllostachys nuda -20

2. P. nigra 'henon' 0 to -5

3. P. nigra 'black bamboo' 0 to -5

4. P. nigra 'bory' 0 to -5

5. P. aureosulcata 'spectablis' -10 to -15

6. P. aureosulcata 'harbin inversa' -10 to -15

7. P. aureosulcata 'aureocaulis' -10 to -15

8. P. Rubromarginata -5 to -10

9. P. Bissetii -10

10. P. decora -10

11. P dulcis - 0

12. P. gluaca 'yunzuh' - 0

13. P viridis 'robert young' - 0

14. Semiarundinaria fastuosa 'temple bamboo' -5

15. S. fastuosa 'fall red' -5

16. S. yashadake 'kimmei' +5 (potted)

17. Fargesia robusta -5

18. F. robusta 'wolong' -5

19. F. rufa 'green panda' -15

20. Pleioblastus distichus -5

21. Pl. pygmaeus - 0

22. Pl. viridistriatus 'dwarf greenstripe' - 0

23. Pseudosasa japonica "japanese arrow" - 0 (potted)

[ShmuBamboo]

I had some other ideas last night after going to bed on this one. One is adding small outdoor christmas lights to your bamboos. These will give off some heat and in many cases, all you need is a little heat. Now these will obviously not help in a blizzard or ice storm, but would make plastic covering more effective and add heat to the plants. There is another device that would help in cold conditions as well; greenhouse heating wire. This stuff is designed to go into the dirt or on the soil. My brother used to use in in his greenhouse up over the 46 parallel to get a jump on spring planting.

Some reasearch I was reading a while ago also mentioned various greenhouse experiments in Siberia that used ground heating wire and ground heating water systems from a boiler. Both had good results, and the idea that they were trying to get across was that it was better to heat the ground than the air in a greenhouse in extreme cold environments for better results. In any event, the wire would work to keep the rhizomes, and presumably the base of the culms of boos from dying from extreme cold. Another similar trick is to put an old tire around the base of a plant and the sunlight will heat it up during the day (if the sun is out and it is not buried in snow).

[ShmuBamboo]

Yah, your temps are about right according to some books I have and the ABS source list. The low temperature seems to vary for the same type of bamboo according to different sources. Seemingly, the numbers you have are the temperatures at which leaf losses generally occur. Most bamboos will usually go lower before cane and rhizome loss. For example, for Phy. nigra 'type' (black black, as it were) that was heavilly mulched: Leaf loss from -10 to 0 deg. F., cane loss from -20 to -10 deg. F., rhizome loss from -30 to -40 deg. F. Compare that to Phy. dulcis that some say will survive (rhizomes and canes) to -20 deg. F., whereas others say that it will suffer heavy rhizome losses at -8 deg. F. I also have some higher numbers for Phy. viridis (all types, including Bob Young). That supposedly loses leaves at 10 to 15 deg. F., canes from -10 deg. F. to 0 deg. F,, and rhizomes from -30 to -20 deg. F.

Temperature variation seems to be dependant on soil type, wind protection, humidity, length of cold spell, snow accumulation, depth of soil frost, size and condition of plants, and if they are mulched or not. Wind protection seems to be a big factor. If you have solid wood yard fences, evergreen tree or other type of wind protection, or they are near the house they stand a much better chance in lower temperatures. And as some of us have said, usually a larger plant that has been potted up befor planting in the ground does a lot better than a baby boo planted in the ground in the fall. I do not as a rule, plant any boos in the ground that were only in gallon pots. I typically plant 5 gallon sized bamboos in the spring, and up to 15 gallon size potted bamboos in the fall, and I have yet to lose any of those in winter (or during summer heat and drought) here. I typically water bamboo plantings in summer drought months here as if they are still in pots for one year so they can get good root growth.

Also a good cold spell here and all the bamboos really take a beating. With a low of 15 degrees for 3 days after an ice storm and snow to follow, my boos all looked rather crappy until spring shooting season came along. Now they are all re-leafed and looking happy again. Hopefully this year will have higher low winter temperatures. 15 was the low this year and last. The year before was a mild 25.

[Mark Meckes]

Having previously grown bamboo in a climate where winter temperatures would consistently go well below 0F (-18C) for prolonged periods, (coldest temp experienced was -26F) my personal opinion is that many minimum hardiness listings (for prolonged cold conditions) are over exaggerated, at least for top hardiness.
Under prolonged cold periods, I would roughly estimate that, at the least, leaf damage will be noticeably visible even at minimum low temps 10-15F or higher than listed.
I would go so far as to say that it's just a fact of life, no matter how evergreen the bamboo is, and even if it does not get to the minimum stated temperature, that there will be a couple of months from late winter into early spring that even established bamboo will have a somewhat scruffy, leaf tattered appearance.
This doesn't bother me, though I anxiously hope that any remaining defoliated branch leaf buds would not have become desiccated and that the previous years culms would releaf, as that would ensure the possiblity of seeing larger new shoots emerge in the spring.

The good news is that, despite total top dieback, rhizomes with adequate snow cover/mulch can survive the below the minimum listed (air) tempertures for the species.

I did find though that some bamboo species (with minimum temperature listing of 0F (-18C) or higher, when experiencing consistent sub-zero F winters would gradually lose their "vigor" over successive years.
I attribute this partially to a symptom I will describe as root/rhizome rot.
Things that can cause this are ...
- Near surface rhizomes getting their eye buds super frozen/losing viability.
- Overly wet spring and soggy conditions.
- Accumulative buildup of dead roots and rhizomes in the core of the planting.
Decomposing rhizomes and roots are a natural part of the recycling nature of bamboo. But a healthy vigorous bamboo is better able to grow away from these areas as they decompose back into nutritional humus, and they have a better circulatory system that draws away moisture and helps prevent anaerobic conditions from persisting.

This above scenario also happens when trying to grow other less hardy perennials at the fringes of their cold hardiness zone.
With these types of perennials it's sometimes necessary to dig them up in the spring, cut out the rotting dead portions and replant the viable portion.
The problem doing this to spring shooting bamboos is that the spring is not a good time to disturb the plant, as it will affect the size/number of shoots Also one does not know the condition of the plant (if all top growth has been totally desiccated) till one sees shoot growth ... or not.

One of the biggest challenges of growing half hardy, less than ironclad plant species is that by their very nature they are subject to the vageries of the seasons.
However with bamboo, if one can get the plant decently established, many less than hardy species will be able to make a comeback.
After all, their known vigor and vitality works in their favor, an attribute that so many of us admire ... others fear. :eek: :p

BTW ... Bamboos grown in one location for a number of years provides an excellent visual indicator of climate changes in your area.

With regards to overwintering a bamboo indoors, we've discussed this here and there in various threads ... the latest being this thread:

Supplemental lighting for overwintering bamboo? (http://www.bamboocraft.net/forums/showthread.php?t=2699)

In a nutshell, if you can't give the bamboo adequate growing/light conditions, plan B is to induce dormancy by keeping it in a cool location, provide minimal watering and hope it survives till the weather sufficiently warms.

I have a couple tropical bamboos which I plant in the ground. They grow to about 10ft tall each year then I dig them up in late autumn, otherwise they will get zapped to the ground here in central Texas.
However the autumn dig causes some leaf defoliation, so this year I decided to keep them in their pots (10gal this year) and then I dug a hole and planted the pots in the ground up to their rims.
I have to water them but not so much as if they were above ground.
This autumn I'll dig up the pots, trim their extending roots or pot them up slightly for the winter and bring them indoors at any danger of frosty weather.
Fortunately we get a lot of warm enough days that I can take them outdoors ocassionally during the winter months.
I get my fair share of exercise hauling our potted plants in and out, come morning and night.
I'm glad the plants appreciate all this effort. :)
Yep, one of these days it would be nice to have an attached greenhouse but I'll settle for it being a pipe dream. I would soon have it bursting at it's seams with a jungle of growth and would be dreaming of a bigger greenhouse.

Mark

[Snowbird]

thanks for all the great info. i'll have to take it all in and formulate a plan. i'll update this thread with whatever i learn by late spring.:)

--seth