Tuesday, December 29, 2009

The killing frost

The fact that the last many winters have been mild in Denmark has made me act with presumption, ignoring several basic rules for growing cacti in freezing conditions. The week before Christmas Denmark was hit by an early cold spell, bringing hard frost that made many of my coldhouse grown plants suffer the consequences of my folly.

Frozen Lophophora williamsii (SB 854; Starr Co, Texas)
Frozen Lophophora williamsii (SB 854; Starr Co, Texas)

The family spent the Christmas holidays in the summerhouse arriving late December 21, the day of the winter solstice. Of course I had to check up on my plants in the coldhouse first thing, but was met by a disheartening sight: The beautiful turgid, dark jade green Lophophora williamsii plants pictured above are frozen solid.

Lophophora williamsii draped in horticultural fleece
Lophophora williamsii draped in horticultural fleece

The greenhouse walls are covered with curtains and the plants are draped in horticultural fleece to protect them from the cold, still the temperature was measured to slightly less than -7 C (~ 19 F) just next to the plants. The temperature alone shouldn't be a problem as these plants have endured conditions in the coldhouse since 2004 (actually these very plants started my experiments in Lophophora cold hardiness so I'm double sad to loose them), but freezing conditions combined with plants that haven't had the time to go flaccid before subjected to the frost is a deadly cocktail. I'm sad to admit that I watered the above Lophophora williamsii plants along with a couple of Gymnocalyciums and two large pots of 3 year old L. williamsii seedlings very late in the season (late September). To make things worse October and November came with a perpetual overcast sky and constant, high humidity levels, leaving the plants no chance to dry out thoroughly. Finally, to top things off, December brought very early and double digit freezing temperatures (measured in celsius) killing off the plants still bloated with water. I have learned my lesson and will never water any of my coldhouse plants later than the end of August (the exception being very young seedlings that might otherwise succumb to drought).

Thawed Lophophora williamsii (SB 854; Starr Co, Texas)
Thawed Lophophora williamsii (SB 854; Starr Co, Texas)

Come Boxing Day the frost went away, leaving me with thawing plants and the possibility to asses the damage – unfortunately I had to leave for home the day after, so the exact casualty figures will follow in a later post.

The thawed Lophophora williamsii plants pictured above felt soft and slightly mushy to the touch but I didn't have the heart to squish them to see if they were fluid inside.

Thawed Lophophora williamsii seedlings
Thawed Lophophora williamsii seedlings

The two large pots of 3 year old Lophophora williamsii seedlings are gone for sure. Upon thawing the seedlings first felt like small bags of slush ice before the interior turned completely fluid. Subjected to a light pressure the epidermis broke and liquid oozed out, indicating that the cell walls are lacerated by the frost.

Frost killed Lophophora diffusa
Frost killed Lophophora diffusa

Another mistake I made was to move new plants into the coldhouse without leaving them sufficient time to acclimatize properly for the winter – the plants were moved to the coldhouse in late September/early October. On that account I lost 3 large Lophophora diffusa like the one pictured above.

As is evident from the flaccid (and very much alive) L. diffusa pictured below, these plants are able to survive the cold conditions if treated properly. The two plants are from the same batch, are growing under the same conditions (and the pictures were taken the same day). The only difference being that the survivor was given proper time to adjust to its harsh environment.

Alive Lophophora diffusa
Alive Lophophora diffusa

I also recently introduced a handful of new Ariocarpus plants to the coldhouse – they had me somewhat worried but seem to cope.

Frost damaged Penis Cactus
Frost damaged Penis Cactus

My last mistake was to leave a collection of columnar cacti out on the terrace until mid October, exposing them to precipitation and moisture for much longer than what's healthy for plants that must winter in freezing conditions. This has taken its toll on my formerly so erect Penis Cactus - I'm not sure if the plant is completely killed off by the frost but it is certainly damaged. I'm worried for the rest of my Trichocereus collection also; many of the plants felt completely frozen to the touch but are not showing any evident signs of damage yet – time will tell, though.


The lesson I have learned from this experience is to always expect the worst from the weather and prepare accordingly (which should have been evident in the first place!). Even if the last many winters have been mild, I should have known that frost can set in suddenly and quite early in Denmark – instead of being lulled into the assumption that most of the winter would be mild with hard frost arriving late, as the situation has been the last few years. I won't be that careless in the future.

After a couple of mild days the weather reports again predict a period of hard, day- and nighttime, frost extending into the new year.

Update, April 11, 2010
Read more about the casualties and survivors of the frost.

9 comments:

  1. I think you will find that the Trichocereus are probably some of the most hardy cacti you have.

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  2. sorry for your loss man. i have lophs this year i lost to rot. very nice specimens. i live in deep south texas where the wild lophs are so they are exposed to a range of conditions but all natural. i even freezing temps for like 3 hours but they seem to ignore it. i bet your temps were worse. once again my condolences on the deceased. they truly become like your children when you've had them for so long.

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  3. I really admire what you doing! Just remember that letting some dies just leaves only the strongest to survive!

    You will soon have "Artic Peyote" :)

    Haha!

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  4. Sara, I sincerely hope you are right regarding the Trichocereus - I checked the plants again a few days ago and many of them are still not showing any signs of damage. Some, especially younger seedlings, have stems that are bent to the ground, though. In previous years I have successfully cut and re-rooted such plants, but the frost is much harder and longer lasting this year than usual (fjords and other inland waters are at risk of freezing over if these temperatures continue much longer - I can't hardly remember when icebreakers were last needed to keep the waters open). To add to my act of hubris, this summer I brought several new Homalocephala, Mammillaria, Gymnocalycium, Ariocarpus and other plants to the coldhouse and started hundreds of plants from seed, so this is indeed turning into a very real experiment in cactus cold hardiness. As you say, the fittest plants will survive - if any of the L. williamsii make it through the winter I will certainly consider 'Arctic Peyote' as a cultivar name for the strain rising out of the mush ;-)

    Anonymous from Texas, thanks for the kind words. I have to say that I envy your location a bit - years ago my work brought me to Texas many times and I was quite enthralled by the land. Actually these visits reignited an old interest in cactus (ultimately resulting in me writing these lines today ;-) Unfortunately my interest fully bloomed only after the visits, so I have walked the Hot Springs Trail in Big Bend without even noticing (or, back then, caring about) the Ariocarpus fissuratus growing along the trail! I would love to visit again, but unfortunately She Who Must Be Obeyed doesn't share my predilection for the Chihuahuan desert, so I'm looking hard for something that might lure her into accepting a Texas desert vacation (I'm considering the cookoffs at the Terlingua International Chili Championship - unfortunately it's rather late in the year, but then again the ariocarpi would be blooming then ;-)

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  5. i live like 40 minutes east of rio grande city and only an hour away from roma. the thrill of finding wild specimens took me to the falcon state reserve. i saw many native cacti all beautiful but no lophs. all my lophs are seed grown. the oldest is 4.

    sometime back they were selling several acre plots in roma. too bad i have my own home because if i didn't i would definitly buy a ranch plot. imagine the the cacti species on hand. makes me giddy. lol.

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  6. Its sad to see all your beautiful cacti die because of the cold. One solution is to make sure the humidity is as low as possible.I have had better luck making sure the humidity is lower during colder weather.Also like you already know,don't water plants any time before a cold snap.I think cacti can survive 5 months with no water and suffer little dammage. If you stop watering before the fall, the soil will be bone dry and if humidity is low the cacti will take much colder conditions than normaly found in cultivation.I have found that cacti love the cold and its only humidity and water that will kill them in the cold.Wish you luck ,cactusman

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  7. Just know that everyone apperciates your hard work, especially mama cacti :)

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  8. Many cacti can survive even for years unwatered. I, for example, kind of "rescued" my dad's collection from years of neglect when I started to have some interest in cacti, but at that time they didn't actually look like they were striving for survive or anything. they were just sitting there living their lives inside a superdry and hot greenhouse.

    Nobody can foresee the sudden weather conditions you had over there, but I think it would be better not to water them at all since middle summer and then wait for the spring to bring back some warmness.

    You can also try wrapping every single pot with horticultural fleece and then the whole again with one additional layer as you did.

    Best luck and hugs!

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  9. All the previous mild winters led to complacency on my part. I actually used to wrap the plants individually in horticultural fleece but not this winter.

    Regarding the watering, I guess I turned "greedy" by seeing the good growth of the plants, not imagining that the coming winter would have long, deep freezes. Of course the situation was worsened by the glum, damp autumn not allowing the plants to dehydrate properly before this extended cold snap set in (it's been freezing constantly since this post was written).

    I have learned my lesson well and will prepare better for future winters (which probably are going to be mild again for the next 14 years;-)

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