cold snap - what croaked, what survived?

Fire · 23 January

I wonder if you have any surprises - plants that held up well or ones that keeled.

My area went down to -8C, for two or three nights, which is as cold as London commonly ever gets. My cerithe seedlings, planted out in the beds, now look very ex. I probably should have kept them in pots so I could fleece them, but didn't realise they were borderline. My cobea also seems not to have made it; -6C was ok, -8C was too much, though fleeced. I will cut it back and see if it reshoots. All my californian poppies seem to have died off, oddly, but they might pop up later in the year. I very much hope so. I have fingers crossed for dahlias in pots and fleeced petunias - running as a trial.

Oddly, bedding cyclamen and violas, put in early September have sailed through even -8C.

https://www.crocus.co.uk/plants/_/cerinthe-major--purpurascens/classid.2000014757/

punkdoc · 23 January

I would have thought it was rather early to determine the damage from the cold spell. It is often not until several months later that the full extent of the damage is realised.

JennyJ · 23 January

Too soon to tell for sure, but my Red Velour petunias look as if they're OK, despite me having (once again) neglected to move them to a sheltered position. I always wonder about the salvias (Amistad and its close cousins - the shrubby ones are hardier I think) and dahlias, and they won't be showing new growth for months yet (if they're not dead, that is).

Fire · 23 January

punkdoc said:

I would have thought it was rather early to determine the damage from the cold spell. It is often not until several months later that the full extent of the damage is realised.

Possibly, but the cerinthe is blackened and withered, the violas and cyclamen are happily blooming away. I was wondering about the immediate, obvious effects of the very cold weather.

As @Papi Jo noted, it's fascinating to watch hellebore go from lying quite flat, splat on the floor to erecting over a day and ending up entirely upright; the camomile too and allium. The red climbing rose buds much have frozen solid but they seem now to be blooming anyway. Quite remarkable.

clematisdorset · 23 January

Your cobea was a legend @Fire, I am sorry it did not make it, but to get this far is good, don't you think? Will you grow it again?

Fire · 23 January

I am amazed. Not that I know much about cobea, but as a tender annual from central America, it's great that -6C didn't faze it. It should have a great root system so I wouldn't be that surprised if it puts on new shoots. I know people grow it into the spring fairly easily in the south of England but usually only if a mild winter.

clematisdorset · 23 January

I hope you get new shoots from your Cobea. You have made me want to try to grow it but I think the erratic wind here might not be good, plus fewer hours of sun in my garden.

It is a shame about your Cerinthe too. There is still time to sow more, I hope. Minus 8 degrees Celsius overnight in your area does seem extreme. Would you say this is unusual. What was it like last winter? I feel as if las winter was worst for me. I haven't used fleece at all yet. I even used hot water bottles last year, placing them around plants in my plastic cold-frame.

We seem to have had two very cold winters in a row. ..El Nino I guess

https://climate.leeds.ac.uk/four-possible-consequences-of-el-nino-returning-in-2023/#:~:text=During El Niño winters, both,ramps up sufficiently by then.

I don't have anything very tender or young in my garden, apart from unknown Pelargonium which have survived (They usually do - I keep them next to house walls in pots).

punkdoc · 23 January

I don’t sow Cerinths until March.

BenCotto · 23 January

Some of the bunches of Erigeron karvinskianus are looking forlorn but I expect them to recover whereas a pot of Nemesia Easter Bonnet is still quite sprightly.

Like JennyJ I also left my Red Velour in situ and I would say virtually all have died; I just didn’t have the verve last Autumn to give them any sort of protection - there was too much going on in my life. However one patch has survived and I’ll soon get round to taking cuttings and propagating it in the greenhouse. I would hate the line to disappear - I have had a production line going from the original six bought in Spring 2017.

Fire · 24 January

clematisdorset said:

I hope you get new shoots from your Cobea. You have made me want to try to grow it.

Germination can be tricky. I definitely had better luck last year than ever before by starting with a plug. I'm sure that's why it flowered from July rather than the autumn, as so many people find. Flower farmers are sowing it now, so that, like chillies, they have enough growing time to fit the whole annual cycle in. They are slow to get going. Florists grow them horizontally for the foliage.

Charles Darwin was fascinated by the lively nature of Cobea scandens. He wrote:

...every part of every branchlet is highly sensitive on all sides to a slight touch, and bends in a few minutes towards the touched side. By lightly rubbing several sub-branches on opposite sides, the whole tendril rapidly assumed an extraordinarily crooked shape. These movements from contact do not interfere with the ordinary revolving movement. The branches, after becoming greatly curved from being touched, straighten themselves at a quicker rate than in almost any other tendril seen by me, namely, in between half an hour and an hour.

I did try to experiment with the touch sensitivity aspect, but as I was dead-heading and trimming the large plant most days I didn't set up the experiment properly. If/when I grow it again I will try to take notes. The tendrils certainly do make beautiful ornate shapes. I didn't find a way to make the cut flowers last well.

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Minus 8 degrees Celsius overnight in your area does seem extreme. Would you say this is unusual. What was it like last winter? I feel as if last winter was worst for me.

I think that last winter, 22-23, had an unusually prolonged period of ice and deep cold and that is what caused the problems. This winter the temps have shot up and down all over the place. It seems a couple of days of cold is much more survivable than a week or more.

It seems that -8C is pretty much as cold as London commonly gets. There are only 13 colder winters recorded since 1963, and that is at the Heathrow weather station which is way out of the city. Last winter hit -8.4C. I believe these temps are measured at head height, so ground temps can be much lower.

https://www.extremeweatherwatch.com/cities/london-heathrow/lowest-temperatures

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The cerinthe were given to me by a friend who has them self-seeding all over her garden. They survived for her last winter but they were in a more sheltered position, by a house wall. I hope some of mine will have come through. Some sites list them as "hardy annuals" and some as tender. RHS says hardy down to -5C.

https://www.rhs.org.uk/plants/103798/cerinthe-major-purpurascens/details

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@Bencotto I'm sorry you and the family have had such an awful year. Your Velour remains a colour inspiration and the focal point of my summer garden. It's 'yours' because you first introduced it to me. I'm hoping a bit of mine will have survived under fleece. I'm attached.

clematisdorset · 24 January

Thank you @fire for your helpful tips and links and beautiful photos.

cold snap - what croaked, what survived?

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