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Palms in Colorado Springs USDA Zone 5b, Page 2
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Photo above, Trachycarpus takil (nainital) at -7F, unprotected. Fronds turn deep black green below 0F, but ~3x increase in cell wall thickness, gain in mass, maintenance of equilibrium, low volumetric soil moisture and high carb/water ratio prevented lethal freeze at temperature below 0F.
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Left, palm frond samples following 64F to -3F event (23-25xi01), from left to right, R. hystrix @ 0.139 with no damage, S. minor @ 0.135 with no damage, T. fortunei @ 0.118 showing ragged spotting from ice crystal rupture of frond tissue, T. fortunei 'greensboro' @ 0.132 without damage.
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Top left, Trachycarpus takil (nainital) unprotected, except by snow, during a -7F event in January 2006. Top right, takil covered by (nainital) canvas tent during December 2005 Arctic front, 36 sustained hours of subzero 0F cold, minimum to -15F. In tent, temperature fell to -9F. We expected lethal freeze of fronds and defoliation, but when temperature rose above 20F, and palms were uncovered, no damage or stress was visible. Bottom right; growth continued through the 2005-6 winter, with each palm maturing one frond and producing one new spear. The -15F cold caused a "crimp" (visible halfway up spear) in each spear. On T. fortunei 'greensboro', crimp is visible as a yellowish ring on the disc, but that mark is absent on takil (nainital).
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Hastulae
The report of a twisted Trachycarpus takil hastula is unreliable for determining this species, because many Trachycarpus have different hastulae, some straight and some twisted, on the same tree.
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How T. takil (nainital) outperformed R. hystrix in 2005-6
Limitation of loss of mass since planting in 2002, by protection when air temperature fell below 0F, lead to observation of some flexibility in Trachycarpus takil (nainital) adaptive range. Mass increased and equilibrium was maintained, and all energy was directed toward growth and achievement of equilibrium. Cell wall thickness increased ~3x, and fronds developed a very thick cover of wax on both surfaces, particularly underneath. Cellular carb/water ratio increased to ~0.140%, in volumetric soil at ~0.070%. During the 2005-6 winter, a true USDA Zone 5 event, the palms were able to withstand -7F unprotected, and -15F protected in a canvas tent, where air temperature fell to -9F, and leaf temperature certainly dropped below 0F. During the 2005-6 winter, T. takil (nainital) outperformed R. hystrix in cold adaptation. During the same events, all R. hystrix were damaged, ranging from minor leaf burn to defoliation and loss of spear. Photos above show takil after all subzero 0F events of the 2005-6 winter.
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Rhapidophyllum hystrix grow more slowly than T. takil (nainital), and may be only slightly more cold tolerant.
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T. takil (nainital) often has a SFH trait (soil frost heave), a sideways growing root that anchors the palm on a slope where frost slip from regular freeze thaw and gravity occur, common among alpine woody plants.
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Above left, at -7F, frond of Trachycarpus takil (nainital) shows deep black-green color. Increased cell wall thickness and elasticity prevent ice crystal formation at temperature below 0F, plus a very thick layer of wax forms over leaf surfaces, most visible underneath (above right). When normal December-January temperatures return, palm regains bright green color, and remarkably, growth continues, unaffected by the means of ~15F low to ~40F high. Limitation of subzero 0F duration, and common winter highs to 50-60F also play a role in winter growth and limitation to lethal freeze.
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Although Trachycarpus fortunei 'greensboro' also shows adaptability to subzero 0F cold, and in fact was the first Trachycarpus we tested to do so, it is not quite as resilient or resistant as takil (sp naini). In "shade," subzero 0F cold produces a crimp in the spear, then a ring of minor damage on the frond. In sun, subzero 0F cold produces the pinhole effect from ice crystals rupturing cell walls, that leads to damage to leaves, but retaining enough energy to recover so the palm functions within equilibrium and achieves actual growth.
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Potash and Epsom Salts were recommended by a Florida grower, who considered these applications to help his palms overwinter and withstand freeze. Application of potash midway through the growing season appears to improve cell wall elasticity, and may increase cell wall thickness. Epsom salts are problematic here because of the already alkaline tendency of our clay soils, and while recommended, have not been used.
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Volumetric Soil Moisture Critical to Cold Tolerance
Palms absorb water incredibly fast and efficiently. They shed water only through transpiration. Carbohydrate-sugar/water ratios in vascular fluid changes incredibly fast with changes in volumetric soil moisture, so the ratio would be best described as a range instead of a figure. Control of the carb/H2O ratio through volumetric soil moisture appears to be a critical factor in cold tolerance. Even in fast draining, permeable soils, palm roots sponge up water so efficiently before it can drain away, a minimal or modest rain or snow can quickly lower the carb/H2O ratio so tolerance of subzero cold is adversely affected. In drought mode, VSM ~0.070%, cell walls thicken and lipid wax production increases as palms gain mass to maintain equilibrium growth.
Minimum temperature cold tolerance of selected palm species based on low volumetric soil
moisture during temperature event. 0.070%
0.143% -14F (Rhapidophyllum hystrix)
0.139% -12F (Sabal minor)
0.133% -7F (Trachycarpus fortunei 'greensboro')
0.133% -7F (Trachycarpus takil)
0.125% -3F (Trachycarpus fortunei)
0.115% -2F (Washingtonia filifera)
0.111% 0F (Serenoa repens)
0.110% 0F (Butia capitata)
0.082% +25F (Howea fosteriana)
Minimum temperature cold tolerance of selected palm species based on moderate volumetric
soil moisture during temperature event. 0.180%
0.138% -11F (Rhapidophyllun hystrix)
0.129% -5F (Sabal minor)
0.125% -3F (Trachycarpus fortunei 'greensboro')
0.125% -3F, (Trachycarpus takil)
Minimum temperature cold tolerance of selected palm species based on high volumetric soil
moisture during temperature event 0.250%
0.132% -7F (Rhapidophyllum hystrix)
0.126% -4F (Sabal minor)
0.122% -1F (Trachycarpus fortunei 'greensboro')
0.122% -1F (Trachycarpus takil)
These models reflect formation of ice within vascular tissues to determine a critical temperature when fatal rupture of vessel walls may occur. Francko, Hirsch, Isakawa and other researchers are measuring cellular protein and fat degradation within individual cells for the same purpose. Figures revised 2006
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RATIONAL ANALYSIS OF CARBOHYDRATE-SUGARS IN VASCULAR FLUIDS OF PALMS IN COLORADO SPRINGS
Samples of vascular fluids were taken from each palm specimen 90 days after the last killing spring frost, 90 days after the first killing autumn frost, and 90 days after the recorded lowest temperature. 30 ml of palm fluid was collected from each specimen, weighed, distilled, and the residue weighed to determine a ratio by weight as parts per 1000. Residue was chemically analyzed by spectrography, to determine that residue were in fact, carbohydrates and plant sugars. The results support the hypothesis:
If a palm has a greater ratio of carbohydrate-sugar to water in vascular fluids, then it can withstand greater stress from subfreezing temperatures.
Control data:
Control plants potted in same soil as the experiment, (Pikes Peak granite loam and Pierre Shale clay mix) kept in a greenhouse window with stable, non-freezing temperatures. Average daily high 72-74F, low 66-68F. An external precipitation gauge determined how much water control plants received, so control and experiment factors
balanced.
Figures are 1/100th percent, data set from 2000-2001
GDD = 2915 (50F base) 3320 (41F base)
Control Set I - continuous irrigation, stable temperature, 4-5 hours direct sunlight
Rhapidophyllum hystrix (Aug) 0.092% (Jan) 0.092% (Apr) 0.093%
T. takil (Aug) 0.08%9 Jan .090 (Apr) 0.090%
Control Set II - winter drought mode, stable temperature, 4-5 hours direct sunlight
Rhapidophyllum hystrix (Aug) 0 .092% (Jan) 0.125 (Apr) 0.129%
T. takil (Aug) 0.089% (Jan) .102 (Apr) 0.108%
Experiment Set I (shaded)
Volumetric soil moisture (Aug) 0.141% (Jan) 0.102 (Apr) 0.136%
Rhapidophyllum hystrix (Aug) .092% (Jan) .127% (Apr) .130%
(visible damage-one plant lost a spear)
Sabal minor (Aug) .091% (Jan) .117 (Apr) .119%
(visible damage - 40% burn on fronds)
Trachycarpus takil (Aug) .089 (Jan) .102% (Apr) .105%
(visible damage- 90% burn on fronds, lost spear)
Trachycarpus fortunei (Aug) . 088% (Jan) .099(Apr) .101%
(visible damage -90% burn on fronds, lost spear)
Experimental Set II (exposed to full sun)
Volumetric soil moisture (Aug) 0.117% (Jan) 0.064 (Apr) 0.102%
Rhapidophyllum hystrix (Aug) 0.092% (Jan) .133% (Apr) 0.138%
(visible damage- yellowing, thought to be chlorosis, now understood to be protective solar discoloration from an acid)
Sabal minor (Aug) .091% (Jan) 0.117 (Apr) 0.118%
(visible damage - 20% burn on fronds)
Trachycarpus takil (Aug) 0.089% (Jan) 0.101 (Apr) 0.113%
(visible damage- 75% burn on fronds, lost spear)
Trachycarpus fortunei (Aug) 0.088% (Jan) 0.097 (Apr) 0.107%
(visible damage - 80% burn on fronds, lost spear)
Temperature data during the period are as follows:
(May-Aug) high temp 96F, low temp 32F, median temp 64F, mean temp 63F, mean high temp 75F, mean low temp 48F, growing degree days = 2305 (50F base)
(Oct-Jan) high temp 74F, low temp -6F, median temp 34F, mean temp 32F, mean high temp 45F, mean low temp 23F, degree days = 96 (50F base)
(November 2000 was the coldest November on record; high temp 62F, low -3F, median temp 29F, mean temp 28F, mean high temp 38F, mean low temp 12F)
(December 2000 data- high temp 49F, low -6F, median temp 27F, mean temp 25F, mean high temp 36F, mean low temp 14F)
(January 2001 was the third coldest mean on record; high temp 36F, low temp -13F, median temp 11F, mean temp 17F, mean high temp 29F, mean low temp 8F)
(During the 2000-2001 winter season, subzero cold was recorded 12 times)
Observations:
August figures show a carbohydrate-sugar ratio when palms were in a healthy growth mode and received plentiful irrigation and natural rainfall. January figures show an increased carbohydrate-sugar ratio as water was with held following killing frosts and freezes, and transpiration decreased the amount of water held in plant tissues. R. hystrix fluids contains the highest ratio of carbohydrate-sugar by weight, and a greater rational increase during freezing conditions. R. hystrix appears to withstand lower temperatures better than other tested palm species. S. minor is very close to R. hystrix in tolerance of subfreezing temperatures, and has a similar fluid ratio. T. takil and T. fortunei have lower fluid ratios, and are less tolerant of subfreezing temperatures than R. hystrix and S. minor.
In frozen soil, R. hystrix was thought to become chlorotic because of yellowing foliage. But only plants in full sun yellow, and then only on exposed surfaces- the underside remains bright green. Chlorosis was ruled out and now presence of an acid similar to tannin is suspected, as a response to increased solar intensity during freezing conditions.
Palms exposed to winter sun performed better than shaded specimens, and had less observable damage.
Vascular fluid was extracted and analyzed within 48 hours of the season low of -13F, to produce a graph of low temperature tolerance potential. Under ideal conditions, R. hystrix can survive to -22F, S. minor to -16F, T. takil to -14F and T. fortunei to -12F, after 2500 degree days (50F base) or 3100 degree days (41F base).
Chemical molecular endothermy is suspected to occur in these palm species. A method to test and measure that is under development for trial during the 2001-2002 winter season. "Warm bloodedness" in some plants is an interesting departure from convention.
Control data:
Control plants potted in same soil as the experiment, (Pikes Peak granite loam and Pierre Shale clay mix) kept in a greenhouse window with stable, non-freezing temperatures. Average daily high 72-74F, low 66-68F. An external precipitation gauge determined how much water control plants received, so control and experiment factors
balanced.
Figures are 1/100th percent, data set from 2001-2002
GDD = 2885 (50F base) 3240 (41F base)
Control Set I - continuous irrigation, stable temperature, 4-5 hours direct sunlight
Volumetric soil moisture 0.180%
Rhapidophyllum hystrix (Aug) 0.122%
Sabal minor 0.118%
Trachycarpus fortunei ‘Greensboro’ 0.117%
Trachycarpus fortunei ‘Bulgaria’ 0.117%
Trachycarpus takil 0.114%
Trachycarpus fortunei 0.114%
Seronoa repens 0.092%
Washingtonia filifera 0.089%
Butia capitata 0.088%
Control Set II - winter drought mode, stable temperature, 4-5 hours direct sunlight
Volumetric soil moisture 0.088%
Rhapidophyllum. hystrix (Aug) 0.130% (Jan) 0.139%
Sabal minor (Aug) 0.124% (Jan) 0.135%
Trachycarpus fortunei ‘Greensboro’ (Aug) 0.124% (Jan) 0.132%
Trachycarpus fortunei ‘Bulgaria’ (Aug) 0.123% (Jan) 0.128%
Trachycarpus takil (Aug) 0.118% (Jan) 0.122%
Trachycarpus fortunei (Aug) 0.113% (Jan) 0.118%
Washingtonia filifera (Aug) 0.106% (Jan) 0.115%
Seronoa repens (Aug) 0.105% (Jan) 0.112%
Butia capitata (Aug) 0.10%0 (Jan) 0.108%
Experimental Set II (exposed to full sun)
Volumetric soil moisture (Aug) 0.089% (Jan) 0.054%
Rhapidophyllum. hystrix (Aug) 0.130% (Jan) 0.139%
No visible damage (Jan 2002)
Sabal minor (Aug) 0.124% (Jan) 0.135%
No visible damage (Jan 2002)
Trachycarpus fortunei ‘Greensboro’ (Aug) 0.124 % (Jan) 0.132%
30% burn to fronds (Jan 2002)
Trachycarpus fortunei ‘Bulgaria’ (Aug) 0.123% (Jan) 0.128%
30% burn to fronds (Jan 2002)
Trachycarpus takil (Aug) 0.118% (Jan) 0.122%
60% burn to fronds, lost spear
Trachycarpus fortunei (Aug) 0.113% (Jan) 0.118%
70% burn to fronds, lost spear
Washingtonia filifera (Aug) 0.106% (Jan) 0.115%
100% defoliated
Seronoa repens (Aug) 0.105% (Jan) 0.112%
100% defoliated
Butia capitata (Aug) 0.100% (Jan) 0.108%
100% defoliated
Temperature data during the period are as follows:
(May-Aug) high temp 97F, low temp 33F, median temp 63F, mean temp 62F, mean high temp 74F, mean low temp 47F, growing degree days = 2375 (50F base)
(Oct-Jan) high temp 74F, low temp 0F, median temp 37F, mean temp 35F, mean high temp 48F, mean low temp 28F, degree days = 228 (50F base)
(November 2001 was the warmest November on record; high temp 75F, low 0F, median temp 37F, mean temp 43.6F, mean high 55.2F, mean low 33.1F, precip 0.42", snowfall 6", volumetric soil moisture 0.068
(December 2001 data- high temp 54F, low 5F, median temp 29F, mean temp 27F, mean high temp 44F, mean low temp 19F, snowfall 2.5”, volumetric soil moisture 0.054)
Observations
22xi01
Projections based on November 2001 data to date (21xi01). An average November at this location (2 Lazy2P Alpine Gardens, Colorado Springs, USDA 5B, 6150' and 5730' alt)(23 years of recorded data):
November data from 1977-2000
Mean high 46.9F, mean low 23.4F, mean temp 35.2F, mean precip 0.55", mean snowfall 5".
November 2001 data:
Mean high 55.2F, mean low 33.1F, mean temp 43.6F, precip 0.42", snowfall 6", volumetric soil moisture 0.068%
There were 96 degree days (method high temp-50F + low temp-50F), or 228 degree days (high temp -41F + low temp - 41F). November 2001 was the warmest November on record, in agreement with NWS data (130 years).
There is no palm damage or stress to record or observe. Musa basjoo and velutina have no more than 20% burn on foliage, several gazania are undamaged and and profusely blooming.
29xi01
Temperature in the root system of the large hystrix following 0F plunge, 1-2" snowfall, is 34F @ 20cm 45F @ 50cm, 57F @ 100cm
As I understand them, 'Greensboro' are seed progeny of a particularly tough fortunei in Greenboro NC. Seedling may or may not carry cold tolerant characteristics of the parent. It is a pure fortunei.
The damage I described is a concern, because never before have these palms here had so much damage so early in the season. The abnormally warm early November did not harden and prepare them for this early deep freeze. The dates and temperatures show the abrupt plunge. Additional GDD accumulation from the warm early November did the damaged fortunei and takil no good.
23xi01 36F and 64F
24xi01 26F and 53F
25xi01 24F and 45F
26xi01 14F and 26F
27xi01 0F and 20F
28xi01 8F and 34F
29xi01 17F and 45F
With temperature rebound to 50F, collapse and damage to palm tissue from a quick 0F event (26-28xi01) and 62+ hour period of freeze became visible. On T. fortunei, rapid formation of ice crystals in leaf vessels resulted in spot damage where ice crystals ruptured vessel and leaf walls, is seen as little white spots, more prominent along leaf edges where damage was most severe. The higher the ratio of carb/water, the less severe the damage. Through microscopy, that damage appeared as if a knife had sliced through vascular and leaf walls, from which fluid bled. Unable to provide water or energy to that portion of the leaf, tissue collapse and dessication began almost immediately. Metabolization of carbohydrates releases energy that sheds primarily as growth, and some degradation in the form of heat. I believe that some plants have an ability to alter, reduce or redirect transpiration during periods of freezing cold, which to a plant is a drought condition, keeping vital carb-rich fluid higher around the trunk and vital buds, thus protecting them. When such carb-rich fluids are withdrawn from ends and edges of leaves, with only water left for transpiration, they are more susceptible to freeze and freeze damage. It almost suggests that at the molecular level, maybe to a degree (no pun intended) at the cellular level, there is an endothermy in some plants.
One more observation! Notice the "yellowing" of the leaf sections, most pronounced on hystrix, lesser on takil and absent on both fortunei and minor. That bronzing is from an acid, similar to the tannin or certain conifers, that appears to work as a sunscreen, shielding sunside chloroplasts from damaging winter UV during periods of freeze. Undamaged fronds return to a normal bright green color during the gowing season, but bronze during winter. The upper surface of hystrix fronds bronze significantly, while the underside remains bright green.
31xii01
Damage from the late November drop to from 62F to 0F: Butia capitata will totally defoliate from that event. Trachycarpus fortunei bulgaria and greensboro have have 30% damage, T. fortunei have 55% damage, S, repens blue have 60% damage, W. filifera have 60% damage, R. hystrix and S. minor have no damage.
December temperature range to date is 52F and 4F. December means are ~4F above normal, (44F and 19F), precipitation is 50% below normal (0.17").
Legend- vii00 (month-year) C/H2O (carbohydrate/water ratio) 0.092 (1/100 percent)
2000-2001 Data
Control 1, mean temperature, moisture mode
vii00 hystrix C/H2O 0.092 takil C/H2O 0.09
volumetric soil moisture 0.141
xii00 hystrix C/H2O 0.093 takil C/H2O 0.09
volumetric soil moisture 0.136
Control II, mean temperature, drought mode
vii00 hystrix C/H2O 0.092
volumetric soil moisture 0.141
xii00 hystrix C/H2O 0.125
volumetric soil moisture 0.102
Set I, USDA 5b temperature, moisture mode
xii00 hystrix C/H2O 0.092, minor C/H2O 0.091, takil C/H2O 0.089, fortunei C/H2O 0.088
volumetric soil moisture 0.117
xii00 hystrix C/H2O 0.122, minor C/H2O 0.117, takil C/H2O, 0.105, fortunei C/H2O 0.101
volumetric soil moisture 0.102
Set II, USDA 5b temperature, drought mode
vii00 hystrix C/H2O 0.092, minor C/H2O 0.091, takil C/H2O 0.089, fortunei C/H2O 0.088
volumetric soil moisture 0.127
xii00 hystrix C/H2O 0.133, minor C/H2O, 0.127, takil C/H2O 0.121, fortunei 0.117
volumetric soil moisture 0.103
GDD= 2915 (50F base) 3320 (41F base)
natural precipitation 18.73"
High 97F, low -13F
2001-2002 expanded data
Set I, USDA 5b temperature, shade mode, drought mode
xii01 hystrix 0.133, minor 0.130, greensboro 0.127, bulgaria 0.127, takil 0.115, fortunei 0.113, filifera 0.105, repens 0.101, capitata 0.1 volumetric soil moisture 0.108
xii01 hystrix 0.139, minor 0.135, greensboro 0.131, bulgaria 0.127, takil 0.12, fortunei 0.117, filifera 0.115, repens 0.111, capitata 0.105
volumetric soil moisture 0.088
Set II, USDA 5b temperature, sun mode, drought mode
vii01 hystrix 0.13, minor 0.13, greensboro 0.124, bulgaria 0.123, takil 0.118, fortunei 0.113, filifera 0.106, repens 0.105, capitata 0.1
volumetric soil moisture 0.089
xii01 hystrix 0.139, minor 0.134, greensboro 0.132, bulgaria 0.128, takil 0.122, fortunei 0.118, filifera 0.115, repens 0.112, capitata 0.108
volumetric soil moisture 0.054
GDD = 2885 (41F base) 3240 (50F base)
natural precipitation 13.18"
high 96F, low -3F
From this experiment, still in progress, it appears when C/H2O surpasses 0.130, a palm has sufficient vascular carbohydrate to withstand subzero cold damage to at least -13F in USDA 5b when volumetric soil moisture is below 0.1 percent. Ratios between 0.120 and 0.130 will result in foliage damage and possible loss of spear. Ratios below 0.120 result in massive defoliation and loss of spear. C/H2O ratio is proportional to volumetric soil moisture, but not temperature.
From the given data, in a drought mode, tested palm species could be expected to survive as follows:
hystrix, minor 5b, greensboro, bulgaria 6a, takil, fortunei 6b, filifera, repens 7a, capitata 7b.
Can filifera, repens, capitata, palmetto or other palms be found with C/H2O above 0.130, or with such potential that could be achieved under cultivation?
One thing this endeavor taught me- God's ability to control all variables and not drop anything is overwhelming.
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