My plan was, to closely monitor weather data and try to spot emergence of cold induced damage on different (more or less) cold hardy bamboos. With gathered data, I’ll be able to determine cold hardiness of each individual bamboo, and detect possible ‘top kill’ conditions or (I sure hope not) conditions where bamboo completely dies. Bamboos are placed in different locations and can have their own micro-climate, but conditions are nearly identical. Small Chimonocalamus pallens seedling is planted under quite large Fargesia murielae, so it’s a bit more protected, but also much more tender because of it’s youth and extremely small size. Actually I will not be able to determine proper values for Chimonocalamus seedling, I will, however, be able to check its hardiness in it’s young seedling stage.

I will closely monitor temperatures and try to write down absolute low temperature (usually morning) and highest temperature. I will add wind conditions information, soil freeze / thaw conditions, information about snow cover accumulation, exposure to full sun, fog, rain, freezing rain… While closely checking weather conditions, I’ll also keep my eyes on all the plants, trying to notice any sign of stress or damage. When weather conditions won’t allow me to identify damage, for example in prolonged period of time with temperatures below freezing or rainy weather that will temporarily re-hydrate damaged leaves, making them look alive, I’ll try to determine the cause and extent of damage when it becomes evident.
I’ll keep all my recordings for further analysis and in try to create easily readable table or chart. Non-threatening days (with temperature above freezing) will be excluded, but will be mentioned as annotation in case of possible impact on plant’s condition later on when freeze damage occurs.

First freeze damage victims: Chimonocalamus pallens and Borinda fungosa seedlings

When temperature dropped and freeze the soil enough (-5°C/+2°C), Chimonocalamus pallens was the first of bamboos that started to show signs of leaf damage. Damage most likely started because of frozen soil and direct sun exposure. Leaves were exposed to full sun and roots were mostly shaded by F. murielae. With day temperature just above freezing, without wind and fully shaded, 1 cm of soil remained frozen. That was enough to damage the leaf cells. Leaves ended up slightly damaged and some of the youngest branches dried out during the first cold spell.
At the same time, the last shoots of Borinda fungosa also started showing some damage. The unbranched shoot is missing the top leaves, but culm still seems to be alive. Spring will tell if branches or buds got damaged. Autumn shoots that branched out recently had shown some damage and had lost a couple of fresh branches, but at least some of them might still be alive. Full extent of damage will also be visible in the spring.

DATA

Bamboo Name
Phyllostachys aureosulcata ‘Spectabilis’
Phyllostachys pubescens ‘Moso’ (3 year old seedling)
Phyllostachys aurea
Borinda (Fargesia) Fungosa (3 year old seedling)
Fargesia denudata ‘Lancaster 1’
Fargesia Murielae
Hibanobambusa tranquillans ‘Shiroshima’
Pseudosasa japonica ‘Tsutsumiana’
Chimonocalamus pallens (1 year old seedling)

Second cold wave.

Just after Christmas, we’ve received another wave of cold air that persisted longer and temperatures dipped much lower. Luckily we’ve received around 20 cm of snow in the beginning when temperatures started plunging. I used that snow cover to tarp down and bury Borinda fungosa which is not hardy enough to survive during harsh winter conditions. Most of the time it was sunny weather with moderate to strong wind. Moso leaves that were not protected by snow started to show signs of freeze damage when temperature dropped to -13°C. When temperature dropped to -15°C, first signs of damage appeared on Hibanobambusa tranquillans ‘Shiroshima’, exposed branches of Phyllostachys pubescens ‘Moso’ seedling got completely fried, Borinda was already tarped and covered with snow to prevent cold air from entering the space between tarp and the ground. Temperatures remained below freezing, but sun managed to melt the snow on south facing positions which caused quite some damage on bamboos that got exposed that way.

Phyllostachys pubescens ‘Moso’ got completely defoliated (perhaps even top-killed) on it’s southern side. Snow cover remained on it’s north facing side, which kept all the leaves and had shown only minor signs of any kind of damage. On January 3rd, snow started melting and temperatures started to rise. When daily highs were above freezing, there was no additional damage on any of bamboos. At the end of the cold wave, southern wind brought warm weather and I untarped B. fungosa to see it’s condition. It was looking surprisingly good. While exposed parts of culms got completely killed, everything that was tarped remained in relatively good condition. Old culms and shoots from late spring/early summer received only up to 30% leaf damage, shoots from early autumn, on the other hand, got up to 90% damaged despite protection.

Result of second cold wave

Chimonocalamus pallens (1 year old seedling) got devastated. Despite being covered with snow and branches of F. murielae, it got completely fried, dried, broken and dead. I still hope rhizomes remained alive so it can ressurect in the spring.

Phyllostachys pubescens ‘Moso’ was also seriously hit. It was covered in snow, but sun managed to expose it’s southern side. Southern side is completely fried, northern side almost undamaged.

Borinda fungosa lost from 20% (mature shoots from spring and last year’s growth) to 90% (youngest shoots) of leaves. It was tarped and bent almost to the ground, which proved to be sufficient protection. All the older shoots survived, late summer/early fall shoots seem to be damaged, but damage can’t be determined before spring. Some of the nodes might still be alive. Tarped and snow covered leaves were only slightly damaged, some started to turn yellow like those in the fall, those that are dead started to dry, most of surviving leaves are green.

Hibanobambusa tranquillans ‘Shiroshima’ had shown quite a lot of damage, but it seems it’s holding well. Snow covered leaves were undamaged, exposed leaves are severely damaged but still show signs of life. Several older culms that were too rigid to get any snow protection seem to be dead.
Phyllostachys aurea is holding well, much better than in 2012 when it got top killed. It does show some frost damage, but most of the culms took the cold surprisingly well. Even some of exposed leaves managed to recover, despite being totally dried out and wilted during the cold sunny weather.

Pseudosasa japonica ‘Tsutsumiana’ got only slightly damaged. Some of the leaves were exposed to cold and were damaged, but they are still alive. It does have several tops fried. They are also water-logged most of the time and they never lost supply of water.

Fargesia denudata ‘Lancaster 1’ is showing some damage as well. It got attacked by voles once again, so it might be vole issue, not the cold alone. I really need to do something about voles.

Fargesia murielae is almost undamaged. It got flattened by the snow, with only middle of the clump partly exposed. When snow melted and some of the branches experienced the cold, it didn’t do much damage to them.

Phyllostachys aureosulcata ‘Spectabilis’ was also almost flattedned despite it’s larger size. I shook it a bit to keep the snow off, so it was exposed to the cold and the sun. It had shown minor signs of damage on youngest shoots during the worst cold, but it recovered. Late autumn shoots that were just starting to branch out in late fall, might be damaged, but are still standing.