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[Saros]

After talking about growing experiences with some other member, I think it would be great to compile a list of Seedian's experiences with various plants and what minimum temperatures that have survived (or died from). I'm not quite sure how I'll organize this yet but since we're getting into the cold season here in the States, I thought it would be a good idea to get this thread started so we can start adding info to it.

Personally, I'm leaving some sacrificial plants out in my unheated greenhouse this winter to see at what point they die. I'm using this temperature logger to keep track of the temperature inside the greenhouse. ***I can't seem to get this logger to work on Windows 7 for some reason***

The "Temp (C)" column is meant to be the lowest minimum temperature reached in that particular environment. For the plants in my greenhouse, it's the minimum temp that the greenhouse reached and maintained for any significant amount of time. If they're outdoor plants, I try to go by the actual minimum temperature reached outside rather than the theoretical zone minimum because some years, it doesn't get close.

The "Hours" column is meant to be how long the plant was exposed to those temperatures.

I think adding any other details about environment would be useful. So if you have any additional information that might be relevant to the plant's survival (or demise), by all means, include it. I'm in favor of collecting as much data as possible even though it's going to be a challenge to display it all.

If anyone wishes to submit data anonymously for 'naughty plants', please PM me with the info and I won't include your name with the data.

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Botanical Name	Lived/Died	Temp. (C)	Hours	Age	Zone	Environment	User
Acacia acuminata	Lived	-8	6		6A	Under cover	prasada
Acacia acuminata	Lived	-5	6		6A	Outdoors	prasada
Acacia acuminata	Lived	-3	6		6A	Outdoors	prasada
Acacia acuminata	Lived	-3.3	6	<1yr	6B	Unheated greenhouse	Saros
Acacia maidenii	Lived	-9			8A	Outdoors	cunningplatypus
Acacia simplex	Lived	0	8			Outdoors	Greentoe
Acacia simplex	Died	-6	8			Outdoors	Greentoe
Agave paryii	TBD	-23					happyconcafe	Severe damage (mushy leaves), Probably died
Alicia anisopetala	Died	-6	8			Outdoors	Greentoe
Alicia anisopetala	Lived	0	8			Outdoors	Greentoe
Anadenanthera peregrina	Lived	0	8	<1yr	6B	Unheated greenhouse	Saros
Anadenanthera peregrina	Died	-2	8	<1yr	6B	Unheated greenhouse	Saros	Leaves stopped opening/closing.
Anadenanthera sp.	Died	-9			8A	Outdoors	cunningplatypus
Argyria nervosa	Lived	-2	8	<1yr	6B	Unheated greenhouse	Saros	Dropped leaves
Argyria nervosa	Lived	0	8	<1yr	6B	Unheated greenhouse	Saros
Ariocarpus	Lived	2.2				Outdoors	New Wisdom
Artemisia absinthium	Lived	-9			8A	Outdoors	cunningplatypus
Asimina triloba	Lived	-9		<1yr	6B	Outdoors	Saros
Banisteriopsis caapi	Lived	12.7	8			Outdoors	Frog Pajamas	Signs of cold damage
Banisteriopsis caapi	Lived	7.2	8			Outdoors	marshmellow
Banisteriopsis caapi (Cielo)	Lived	1.6	8	1yr	6B	Outdoors	Saros	Slight drooping to leaves. Soil was also dry, so that may have been the cold or lack of water.
Banisteriopsis caapi (Cielo)	Lived	2	8	<1yr	6B	Unheated greenhouse	Saros
Banisteriopsis caapi (Red)	Lived	2	8	1yr	6B	Unheated greenhouse	Saros
Banisteriopsis caapi (White)	Lived	1.6	8	1yr	6B	Outdoors	Saros
Brugmansia	Lived	7.77				Outdoors	Greentoe	In ground, died back to roots
Brugmansia sp.	Died	-9			8A	Outdoors	cunningplatypus
Calea zacatechichi	Died	-9			8A	Outdoors	cunningplatypus
Calea zacatechichi	Lived	1.6		<1yr	6B	Outdoors	Saros
Centella asiatica	Lived	-9			8A	Outdoors	cunningplatypus
Desfontainia spinosa	Lived	-9			8A	Outdoors	cunningplatypus
Heimia salicifolia	Lived	-9			8A	Outdoors	cunningplatypus
Heimia salicifolia	Lived	-6	8	<1yr	6B	Unheated greenhouse	Saros	Died back to roots
Heimia salicifolia	Lived	-18		1yr	6B	Unheated greenhouse	Saros	Died back to roots. Leafs re-emerged 4/10
Ilex paraguariensis	Lived	-9			8A	Outdoors	cunningplatypus	Died back to roots
Iochroma australe	Lived	-9			8A	Outdoors	cunningplatypus	Died back to roots, regrew quickly
Leonitis leonurus	Died	-6	8			Outdoors	Greentoe
Leonitis leonurus	Lived	0	8			Outdoors	Greentoe
Lophophora	Lived	2.2				Outdoors	New Wisdom
Mammillaria	Lived	2.2				Outdoors	New Wisdom
Melaleuca alternifolia	Lived	-9			8A	Outdoors	cunningplatypus
Mimosa hostilis	Lived	2	12		9B	Under cover	MadPlanter
Mimosa hostilis	Lived	4			9B	Outdoors	MadPlanter
Mimosa hostilis	Died	-5	8	1yr	6B	Unheated greenhouse	Saros	Dropped most of it's leaves
Mimosa hostilis	Lived	-2	8	1yr	6B	Unheated greenhouse	Saros	Leaves stopped opening/closing, but bounced back after 1wk indoors.
Mimosa hostilis	Lived	0	8	1yr	6B	Unheated greenhouse	Saros
Mimosa hostilis	Lived	1.6	8	2yr	6B	Outdoors	Saros
Mitragyna speciosa	Died	-9			8A	Outdoors	cunningplatypus
Monarda didyma	Lived	-18		<1yr	6B	Outdoors	Saros	Died back to roots mostly. A few tiny leaves around base stayed green.
Mutucana	Lived	2.2				Outdoors	New Wisdom
Myrtillocactus	Lived	2.2				Outdoors	New Wisdom
Neoporteria	Lived	2.2				Outdoors	New Wisdom
Nicotiana alata	Lived	-2	6	<1yr	6B	Outdoors	Saros
Nicotina rustica	Lived	-9			8A	Outdoors	cunningplatypus	Died back to roots
Opuntia	Lived	2.2				Outdoors	New Wisdom
Passiflora caerulea	Lived	-5	8	1yr	6B	Unheated greenhouse	Saros
Passiflora caerulea	Lived	-18	8	1yr	6B	Unheated greenhouse	Saros	Died back to roots.. It was in a pot sitting in the corner of a raised bed in my greenhouse. Last year it grew roots through the bottom of the pot and firmly planted itself in the bed. The potted portion of the plant died during the winter. I thought the whole plant died until I noticed passiflora growing out of the complete opposite side of the bed. Apparently it lived on under the soil in the bed and came back from the roots.
Peganum harmala	Lived	-18	8	<1yr	6B	Unheated greenhouse	Saros
Phalaris aquatica (AQ1)	Lived	-3.3		<1yr	6B	Outdoors	Saros
Phalaris aquatica (AQ1)	Lived	-18	8	<1yr	6B	Unheated greenhouse	Saros
Phalaris arundinacea (Big Medicine)	Lived	-3.3				Under cover	PermieGing
Phalaris arundinacea (Big Medicine)	Lived	-18	8	<1yr	6B	Unheated greenhouse	Saros
Phalaris arundinacea (Yugo Red)	Lived	-3.3	8	<1yr	6B	Unheated greenhouse	Saros
Polaskia	Lived	2.2				Outdoors	New Wisdom
Psychotria "nexus"	Lived	10	8			Outdoors	Sunshine
Psychotria alba	Lived	-6	8			Outdoors	Greentoe	Died back to roots.
Psychotria alba	Lived	0	8			Outdoors	Greentoe
Psychotria alba	Lived	7.2	8			Outdoors	marshmellow
Psychotria alba	Died	-5	8	<1yr	6B	Unheated greenhouse	Saros
Psychotria alba	Lived	0	8	<1yr	6B	Unheated greenhouse	Saros
Psychotria viridis	TBD	10	8			Outdoors	Sunshine	Extensive cold damage to 8" juvenile plant
Punica granatum	Lived	-9			8A	Outdoors	cunningplatypus	Hawaiian seed
Punica granatum var. nana	Lived	-6	8	2yr	6B	Unheated greenhouse	Saros
Salvia divinorum	Died	-9			8A	Outdoors	cunningplatypus
Salvia Divinorum (bunnell)	Died	-2.2				Outdoors	Seed Collector
Salvia Divinorum (la fuerza)	Lived	2	8	<1yr	6B	Unheated greenhouse	Saros
Salvia Divinorum (la fuerza)	Lived	1.6	8	1yr	6B	Outdoors	Saros
Silene capensis	Lived	-17.8			7A	Outdoors	Auxin
Silene capensis	Lived	-18		<1yr	6B	Unheated greenhouse	Saros
Tephrocactus	Lived	2.2				Outdoors	New Wisdom
Trichocereus	Lived/Died	-9			8A	Outdoors	cunningplatypus	In ground. wet winter. living cactus developed tip rot but bounced back in the spring.
Trichocereus	Lived	2.2				Outdoors	New Wisdom
Trichocereus bridgessii	Lived	7.77				Outdoors	Greentoe
Trichocereus candicans	Lived	7.77				Outdoors	Greentoe
Trichocereus glaucas	Died	-12.7			8A	Outdoors	Auxin	3 day cold spell of -13.3, -12.7 , -12.2C weather. Froze solid.
Trichocereus macrogonus	Died	-12.7			8A	Outdoors	Auxin	3 day cold spell of -13.3, -12.7 , -12.2C weather. Froze solid.
Trichocereus pachanoi	Lived	7.77				Outdoors	Greentoe
Trichocereus peruvianus	Lived	7.77				Outdoors	Greentoe
Trichocereus terscheckii	Lived	-12.2	8		8A	Outdoors	Auxin	Repeated nights at -6.6C
Trichocereus terscheckii	Died	-12.7			8A	Outdoors	Auxin	3 day cold spell of -13.3, -12.7 , -12.2C weather. Froze solid.
Voacanga africana	Lived	0	8	<1yr	6B	Unheated greenhouse	Saros
Voacanga africana	Died	-5	8	<1yr	6B	Unheated greenhouse	Saros	Leaves curled and froze solid

13 Likes Mandrake, Seed Collector, Sunshine, Greentoe, prasada and 8 more people like this.

[Mandrake]

A reference guide for plant hardiness in regards to temperature would be very useful. Most of us have wondered whether one plant could be safely left outside during the winter, or whether we should plant it outdoors at all. I'd surely look forward to resolve these issues with a data list and a thermometer.

Both information sourced in good literature and personal experimentation, specially around valuable plants for the community, will be very welcome.

Thank you for the thread,

Mandrake

1 Like Sunshine likes this.

[Sunshine]

I just set one of my rooted la fuerza salvia cutting outside, out of the wind. It is around 4 inches tall. The current temperature is 47F and the time is 3:37pm. I'll update if anything changes.

1 Like PermieGing likes this.

[Saros]

It might also be useful to make note of how long the cold temperatures last when possible.

I suspect that one of the reasons my Heimia s. survived all winter long in the unheated greenhouse was because the lowest temperatures didn't last more than 8 hours or so. After sundown, the temps slowly drop until it just about equalizes with the outdoor air. Then as soon as the sun hits it in the morning, it quickly heats up again. If it didn't jump back up above freezing each day, I'm not so sure they would have had the same survival rate.

1 Like prasada likes this.

[MadPlanter]

The mimosa hostilis I have here have survived multiple days of straight exposure to 40F or slightly lower at night. I do however bring them at least under cover at below 35F. Maybe they could handle it but I just am afraid to hurt them.

[cunningplatypus]

Saros,

An excellent question! I've also been experimenting to see what manages to hang on through the winter. I've taken some casualties, but it's all in the name of science. 

I live in the Pacific northwest, zone 8a (minimum temps 10 to 15 degrees Fahrenheit). Winters are very wet.

Here are some success stories for me from last winter, as well as some failures. Everything was in-ground, exposed to the elements.

Success in hardiness zone 8a

Iochroma australe (died back to the roots, regrew quickly)
Ilex paraguariensis (Yerba mate. Died back to its roots, which is not ideal for slow-growing, foliage-valued plants)
Heimia salicifolia (Sinicuichi)
Melaleuca alternifolia (Ti Tree)
Acacia maidenii
Punica granatum (Pomegranate, Hawaiian seed)
Centella asiatica (Gotu kola, one of the varieties)
Artemisia absinthium (Wormwood, no surprise)
Nicotina rustica (died back, but lived!)
Desfontainia spinosa

Failures

Salvia divinorum
Mitragyna speciosa (no surprise, really)
Calea zacatechichi
Anadenanthera sp.
Brugmansia sp.

Mixed success/failure would be my in-ground Trichocereus cacti.

They took the full rain assault all last winter, completely exposed to the elements. None died, but almost every one developed tip rot. They all recovered nicely, and pumped out the pups this summer.

This winter, I'm trying to overwinter in-ground...

Psidium cattleianum (Strawberry Guava)
Psychotria alba
Moringa oleifera (Drumstick Tree)
Silene capensis (Dream Root)
Withania somnifera (Ashwaganda)
Andrographis paniculata

I think there are a lot of variables that may make or break a plant's survival in marginal areas. Most importantly, I'd hazard that proper mulching might make the difference.   

[Sunshine]

Its been 2 hours. The temperature has dropped 3 degrees and it is now 44F. The plant looks fine. I'll leave it for a few more hours.

[fairdinkumseeds]

I don't have much cold weather gardening experience, (or plan on getting any if I can help it.) But was told by an "expert" friend that mulching with lawn clippings was a good way to protect plants from the heavy frost, so I rushed around and mulched all the seedling fruit trees in couple rows as there had been frost predicted a couple months after we first arrived.
We had a big frost (well big for here) and the ones without mulch, which I didn't end up getting done in time, only about 10%-20% got a bit of leaf damage, nothing serious, but the ones with a thick donut of lawn clipping only 60% lived, mostly the stonefruit, and they all got really hammered, looked crook and died back. Same plants in both lots of rows, same open flat ground. Various guavas, custard apple, jackfruit, moringa, dates and stone fruit mostly.
I think the steam from the fresh leaf matter caused more ice on the roots and trunk? Whatever was the cause, I don't recommend fresh lawn clippings! Wasn't happy at all.
I would have thought that the moisture would trap heat and take longer for the temp to drop, but now I reckon that dry is better for some reason. Maybe less conductivity?

[Sunshine]

Going on 4 hours and the temp hasn't dropped any in the last 2. Its still 44F and it looks fine. No doubt it would grow slower at temperatures this low. I don't think it would die though.

[Auxin]

Silene capensis survives semi-arid zone 7a winters without protection, mine are actually flowering again right now after the first frosts.

1 Like Saros likes this.

[Saros]

Auxin, that's great to hear. I suspected they would hang in there longer than most. Mine are blooming like crazy right now as well. Hopefully I'll have a bunch of seeds to share soon:)

1 Like Caium likes this.

[PermieGing]

Something that could inspire some scientific experimentation is putting some of these somewhat questionably cold hardy plants near lots of stone, like a stone wall or in the middle of a bunch of stones on the ground. The stones theoretically absorb solar heat and release when not exposed to the sun...

Food for thought

[Sunshine]

Its been 7 hours since I put it outside. It is now 43F. Its supposed to get down to 30F tonight so I'm going to bring it inside. We'll see tomorrow morning if the cold effected it.

1 Like PermieGing likes this.

[prasada]

 I took some readings of  Acacia Acuminatas last night . The predicted low was -4c.
  Used a digital thermometer with three probes, one in soil,one for inside ambient temp and one for outside ambient temp. The plants ,in pots ,have remained outside for light and temperature acclimation .

 At 8pm     soil temp= 41.3f/5.1c     at 3am  34.5f/1.3c   at 5am 32.7f/.38c    at 9am 31.1f/0.4c
indoor ambient air  =36.8f/2.7c                   30.9f/-0.5c               32.5f/0.27c              45.1f/7.2c
outdoor ambient temp35.3f/1.7c                 29.1f/-1.6c               27.6f/-2.4c               31.7f/-0.16c

 so it looks like soil temp went below freezing , but i would suspect there is still some latent heat coming out of the water as it changes state  from a liquid to solid, some components of the soil could be colder than the water.   This cant be compared to a plant in the ground that is buffered by the earth temp.
 Oh yea ,the plants look fine.

2 Likes Greentoe and PermieGing like this.

[Saros]

prasada, that's great to be able to get such detailed measurements. I need to get myself a thermometer for soil as well. That might be an interesting number to keep track of for this.