Minimum Temperature Rating System

[Thuja]

Bamboo survival in cold weather is dependent on a variety of factors besides temperature. Factors such as siting: wind, humidity, cold exposure time, winter sun, etc.; culture: mulching, watering, fertilizing, soils, etc.; winter acclimation; etc., all figure into plant survival. Therefore it's probably next to impossible to assign a single number which will tell us definitively whether a plant shall live or die when exposed to a particular low temperature. Even so, most books and nurseries list minimum temperatures that bamboos can survive.

So why are the numbers even published?

Can this system be improved upon?

[needmore]

Mike, I agree that a temp rating is probably not the best way to approach bamboo growth. I told Bill H. last year that I hope to someday create a map with growth projections that is something of a hybrid between the USDA zone map, the Sunset Zone map and a bamboo database. What I envision is building a database with 'normal' environmental ranges for various parts of the country including a blend of coldest temp, hottest temp, annual precipitation, length of growing season, humidity norms, snow cover days etc. Then within a reasonable variance factor, combine locales with similar enough data and color the map as per the USDA style hardiness ratings.

Integrate this database with an additional database with actual performance data of mature plantings for each species, for each of the new 'zones'. Then each species of bamboo would refer to the colored zonal map with a legend/key.

For example, Nigra - in 'green' zones this bamboo should emerge from most winters with minimal damage and will mature in the 25 feet by 1 1/2 inch range with an aggressive spread rate. In 'red' zones this bamboo will sustain significant damage most winters and will remain compact in the 8-12 feet by 3/4 inch range, the desired black culms will rarely be present due to environmental issues. In 'yellow' zones this bamboo will not likely survive winter and another species should be considered.

Blah, blah, blah,...I'm not quite totally wired in to this idea yet and it is a big undertaking, but dang it, I can just the thing in my mind....

[foxd]

It would seem to me that Wind Chill and Heat Index would be better choices than Min and Max Temp for the charts. It would keep the charts simple and at the same time account for the effects of wind on the bamboo during cold months.

[bambooweb]

Collecting survival information is part of the idea behind the Growth Data section of this website. Unfortunately I have not had time to finish some output screens but you can enter you data. It is not yet set up for metric information.

In the Species list printed version the unknown values are left blank. Sometime in the past the unknown values were blank in the *F field but were converted to -18*C. This was corrected last year so the *C is also blank.
This site uses 'U' for Unknown values and the PocketPC version of the species list uses 999 for an unknown low temp.

Another thing that affects hardiness is the timing of the low temperature. A cold snap in late Fall does more damage than in late Winter because the plant has adapted to low temperatures.

Bill

[Thuja]

All these ideas sound great. Brad's map idea would be ideal. This site's Growth Data will be interesting to see as it develops. There's nothing as valuable as a neighbor's shared experiences growing a particular plant, so having access to this information will be valuable. E.g., on Gardenweb, I saw a photo of P. nuda being grown in Milwaukee, so from this I do know that it is possible to get a fairly good-sized nuda plant to grow in southern Wisconsin. By comparison, looking at a -20*F rating on ABS's source list is encouraging but not quite as conclusive.

The effect of wind on bambooo is problematic. Personally, I see wind-chill temps being related mostly to foliage retention. I think that bamboos can be thought of as broadleaf evergreens, and hence need the same sort of protection from dry winds and winter sun that we normally associate with growing plants like boxwood, Rhododendrons, holly, and the like. There is somewhat of a difference tho with bamboo in that if the entire plant gets defoliated during a winter blizzard or bitter winter, the bamboo plant, if mulched well, can recover in spring by releafing or by shooting new culms.

In thinking about cold hardiness ratings related to growing bamboo, I think there are at least 3 distinct levels that bamboo growers are interested in:
1. leaf
2. culm
3. rhizome

Wind (winter sun, etc.) is going to affect leaves the most, culms probably not nearly as much, and rhizomes maybe not at all. Most often books and growers seem to list "leaf-kill" temperatures rather than "culm-kill" or "rhizome-kill" temperatures. E.g., the ABS Species Tables' (http://www.americanbamboo.org/SpeciesSo ... ciesTables) states that:

The ?min temp? column entries for subtropical bamboos give an estimate of a one-time brief minimum temperature that can be tolerated with only leaf loss in well-established plants on a calm night, in areas where the daytime maximum temperature is substantially higher.

I would interpret this as saying this rating system lists "leaf-kill" minimum temperatures for perhaps the southern US area.
The question I have is why list leaf-kill temperature? Why not list culm-kill temperatures instead? The hardiness zone rating system works quite well for trees and shrubs. Listing culm-kill temperatures would make bamboo appear more like "regular" trees or shrubs and thereby would fit better in the hardiness zone system.

I suppose this suggestion might reflect a northern grower's perspective but could have more universal use.

Related question: How different are leaf-kill and culm-kill temperatures? I think it is species-dependent & very variable, but on average it seems like it might be at least 5-10*F?

[rfgpitt]

I have grown to better understand the rating system with lots of invested time. What I would like to see, and what I think anyone who is interested (newbies) in growing bamboo would benefit from is pictures. Show me pictures of poor looking bamboo after winter has damaged them, and explain what caused the problem. I have seen very little evidence of cold weather related damage posted anywhere. To me, as a gardener and former landscaper, seeing something with a defoliation rating of -20*f would mean that in a zone 6 environment the thing would be invincible, but that is not the case.

[Thuja]

I've got plenty of damage to photograph. I'll have to document some of it. Brad has some cold damage photos on his website http://www.needmorebamboo.com/
Here's what some nuda leaves look like after a low of 5*F so far this November...
<img src="http://www.bambooweb.info/images/bamboo ... Small).jpg" alt="PHYLLOSTACHYS nuda ">
Most of the time the thought doesn't occur to take photos of something that looks bad.

[bambooweb]

Yellow Groove
Plant on right- 2 year old plant from #1 pot. Plant on Left- Field dug plant planted in 2003. Photo taken in spring of 2004 after low temp of -24*F.

<img src="http://img.photobucket.com/albums/v134/ ... ck2004.jpg" alt="Image hosted by Photobucket.com">

Bill

[Iowaboo]

Last weeks coldest recorded temp. was 7 degrees F on our hill. May have been colder in the valleys where my bamboo shall get the onslaught of nature's tough love.

All the bamboo had some leave damage. The two that had very little damage was rubro, Bissetii and aureosulcata. Nuda and Flexousa had major leaf damage on the highest leaves on the culms. Aurea had medium leaf damage.

[Mike McG]

Mike,

I am sure in part your post was meant to prompt discussion and I hope you would agree the temperature listed by the ABS is better than nothing. I use it as a relative number to compare one bamboo to another but nothing beats the specific experience growing a specific plant, yours, your neighbors, or someone in a similar climatic condition.

As many plant enthusiests do, I keep inching up to less and less hardy plants. I think the "Tropicals" guys are even worse about this and the extent to which they will go to grow say palms in NJ. I sure I will be caught with major damage to my Bambusas one of these winters, but I am hopefull that very few will die. I try to keep them well mulched. I do grow many plants, including some 6-7 ft high bushes, here in TX as die back perenials. The trunks die and then regrow every year.

I also grow some cycads and face a similar problem as with bamboo, degree of frond damage vs caudex death, except in most cases, caudex death is plant death. Some of you may be familiar with the CRDB for palms and cycads. Here for example is the link to data on Cycas revoluta, aka Sago Palm.
http://tct.netfirms.com/cgi-bin/crdb/cr ... Bank=Cycad
A summary for cycads is at:
http://tct.netfirms.com/cgi-bin/crdb/cr ... Bank=Cycad
Like everything it could be improved, but I have found this database to be very useful, along with other data, as a screening tool on what I might consider growing here.

For many of the bamboo too high a temperature can kill them as easily as too low so there are certainly other parameters such as shade and water needed for bamboo. At this point with the limited (or scattered) data, listing success growing a certain bamboo in a certain area may be a useful as where you killed it. I am certainly willing to contribute to such a database for bamboo.

Mike near Brenham TX

[Thuja]

The best rating system I've ever seen for bamboo is one used by David C. Andrews of the DC area. http://bambooweb.info/ShowFilterSources ... &Button=GO

He uses a grading system from A-F.
A: Most leaves survive.
B: Most old culms survive.
C: Most new culms reach or nearly reach normal size.
D: All new culms grow below normal size.
F: Rhizome death (plant dies).

For example he lists P. nuda as AB-4 B-7 BC-8. This means that its foliage starts to suffer at -4*F and dies at -7. Culms begin to die at around -8*. David's hardiness ratings seem to me to be more accurate than any I've seen, at least for someone trying to grow bamboo in cold climate areas.

[rfgpitt]

Thuja,
do you have a link for that info? only an e-mail addy was given....

Thanks,

[Thuja]

Rick-- He doesn't have it posted on a website as far as I know. All the hardiness ratings are on his price list which you can get by email from him or snail mail in exchange for a SASE. I'd copy and paste it here but would need to ask his permission first.

[Mike McG]

Mike,

I agree David Andrews' system using A & B certainly is an improvement over the ABS single temperature, but I think it starts to breakdown on C, D, & F where duration at a certain air temperature or soil temperature are probably more important. Whatever system is used needs to have easily obtainable parameters for the local area, lacking area specific experience with that or a similar species.

Firstly, I think any system such as this needs a temperature where essentially no damage occurs. I realize in Zone 4 you are probably looking for long-term bamboo survival, but I would expect that many people using such a list would be growing bamboo as an evergreen ornamental and interested in knowing where it would be damage free most winters. This temperature or zone would need to be broken down further into shaded locations and sunny locations.

Secondly, I am not sure what effects culm size in C & D. Is this an effect of length of growing season, bamboo species, soil temperature, ect? Would air temperature coupled with number of frost free days be say a better indicator of areas allowing bamboo to recover from winter culm death?

Thirdly, for bamboo in the ground, as opposed to pots, I would think duration at temperature is even more important than an instantaneous air temperature for rhizome death. Here in Zone 8b TX it can be 18 F at 6:00 am and over 40 F by Noon. The 18 F is importantant for above ground damage but does not have much effect below the mulch. Ponds almost never get any ice on them, puddles sometimes do. People frequently have well tanks exposed outdoors. The point I am trying to make (in a long-winded fashion) is that if we got several days here at 25 F it would be a much bigger problem than a brief. hourly dip to 15 F. Maybe freeze depth from the local building code might be a good indicator but I am not sure it is readily available to most people, so maybe average weekly of monthly temperature might be a better indicator of long term low temperatures that would pentrate into the ground?

Mike near Brenham TX

[kstanwick]

I hear ya about the min temp thing...Since i have been growing bamboo...this will be my third spring...I have decided to take people's advice vs going with a rating....hence the importance of this and other forums. Most of the bamboo i recieved were z7(first season)...and i know now for sure i am a z6.... lol....so i'm going with what works....especially just trying to get something going....overall it is a good guideline if you have no one to ask...but we have Brad....lol