Perhaps what we need is better labelling on plants, with the RHS UK hardiness ratings as a minimum, that way people would know when they're taking a risk with a less than fully hardy plant.
I'm surprised this information isn't on labels; it's standard here for perennials at least. We have the USDA plant hardiness zones and labels will have the zone hardiness or the lowest temperature the plant can tolerate. ...
Maybe it is. It's a while since I bought a plant from a garden centre that I wasn't already reasonably familiar with. Perhaps people don't always read them, or choose to take a chance on not-fully-hardy things. And it's not just low temperature that kills plants, it's wetness at the roots when a low temperature hits, so for example in my well-drained soil I'm usually OK with plants down to RHS hardiness rating H4 planted outside, and very often H3 will be fine too, as long as they're plants that will grow back from the roots after the top growth has been killed.
I suspect a lot of the cordylines and suchlike that people think they've lost will grow back from ground level, but it's a case of wait and see for the next couple of months.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
There have been an awful lot of threads about plants that have been damaged or even killed by frost. I think a more general discussion might be of interest.
Frost.
There are two types of frost (perhaps more): Ground frost and air frost:
Ground Frost, grass frost.
If the temperature of the ground falls below 0 °C then this is a ground frost. Ground frosts are common even when air temperatures are above 0 °C. Ground frosts occur when the sky is clear and daytime heat is radiated and not reflected back by clouds. I am careful with any forecast of air temperatures <4ºC if the day has been sunny.
Air frost
If the temperature of the airfalls below 0 °C then this is an air frost. It is very unusual for an air frost to occur when ground temperatures are above 0 °C.
If humidity is high, both types might result in mist, fog and hoar frost/rime.
Plant hardiness.
Sap and moisture in stems and leaves freezes, and in so doing the crystals will expand and burst the plant cells resulting in localised death.
Different plants have different strategies for combating freezing temperatures.
1. Avoid cold climates.
2. Go dormant. Shed leaves and go underground.
3. Have antifreeze chemicals in the sap and other plant parts.
4. Have stong cell walls that resist bursting.
It is well know by gardeners that Dahlias die at the first slight frost, but their tubers survive underground. Many succulents like Aeoniums will suffer from a mild frost but others like sempervivums will survive down to -30.
Some woody plants that go dormant may wake early and be affected by a late spring frost when the sap is rising . Hydrangeas can be damaged in Surrey by a frost as late as June.
Protection.
1. Take indoors or into a heated greenhouse.
2. Take more hardy plants into a cold greenhouse. And dormant plants into a dark but frostproof shed.
3. Cover, Insulation. But note that insulation only slows down cooling, not stops it. In a prolonged or a deep freeze the cold will get in.
Be Prepared:
Follow weather forecasts from November onwards. Perhaps early in some parts.
I'd add a sub category to this; Wet Frost, i.e. a frost after heavy rain. This is the one I fear the most.
I'd add a sub category to this; Wet Frost, i.e. a frost after heavy rain. This is the one I fear the most.
Thank you to adding to my list. I knew it wasn't the be-all-and-end-all.
But I am not familar with this phenomenon. Is it a bit like heavy snow? Thw weight dragging the plant down? Usually I rgard rain as a saviour, guaranteeing that the plant temperature will not fall below zero.
location: Surrey Hills, England, ex-woodland acidic sand. "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
But I am not familar with this phenomenon. Is it a bit like heavy snow? Thw weight dragging the plant down? Usually I rgard rain as a saviour, guaranteeing that the plant temperature will not fall below zero.
Other way round, so heavy rain, then the skies clear and you get a sharp frost the next day/night while the rain is still on the plants. It's the worst thing for some plants that have a tight rosette or cup form. These may be very cold hardy but won't survive having an ice cube sitting in their hearts. Some desert succulents are especially prone to it but there are others, too
Gardening on the edge of Exmoor, in Devon
“It's still magic even if you know how it's done.”
Very common here - wet then freeze. Frosty and dry does far less damage than frosty/icy after wet. It's also not as simple as just a period of frost, any more than it's just as simple as a period of strong sun/heat. It's what happens over longer periods of time. That has a far greater impact on plants.
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
I am concerned that my plum tree (a 'Czar') has recently shown two flowers. It has never flowered before. Do you think these flowers are likely to be 'testers' where the tree checks the conditions? Also, is it likely a bad frost could stop it from issuing anymore flowers at all this season?
Sorry to witness the demise of the forum. 😥😥😥😡😡😡I am Spartacus
I'd add a sub category to this; Wet Frost, i.e. a frost after heavy rain. This is the one I fear the most.
Thank you to adding to my list. I knew it wasn't the be-all-and-end-all.
But I am not familar with this phenomenon. Is it a bit like heavy snow? Thw weight dragging the plant down? Usually I rgard rain as a saviour, guaranteeing that the plant temperature will not fall below zero.
Usually when a cold front blows over preceeded by rain and followed by clear skies. Or the sleet we're having here this morning which is forecast to freeze tonight.
Wet crowns and leaves that freeze is a death knell to certain tenders that would ordinarily survive a freezing dry period.
But I am not familar with this phenomenon. Is it a bit like heavy snow? Thw weight dragging the plant down? Usually I rgard rain as a saviour, guaranteeing that the plant temperature will not fall below zero.
Other way round, so heavy rain, then the skies clear and you get a sharp frost the next day/night while the rain is still on the plants. It's the worst thing for some plants that have a tight rosette or cup form. These may be very cold hardy but won't survive having an ice cube sitting in their hearts. Some desert succulents are especially prone to it but there are others, too
I can understand this freezing after rain phenomenon now that it has been described. Water lodged in a confined space would expand on freezing and so damage the entrapping plant parts. But I have never experienced it.
I have always regarded water in freezing guaranteed that the temperature would not fall below zero. (Latent Heat and all that.). And most plants can take -1 or 2. One never stops learning.
location: Surrey Hills, England, ex-woodland acidic sand. "Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
I notice a fair bit of damage from prolonged frost, coupled with drying winds - turns out this has a German name “Frosttrocknis,” or frost desiccation. On evergreens, the leaves can be actively transpiring during the day, but a frozen rootball cuts off water supply, hence the plant defoliates due to drought. I reckon a lot of these brown, frazzled looking hebes people are complaining of have been affected like this.
"What is hateful to you, do not do to your neighbour".
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But I am not familar with this phenomenon. Is it a bit like heavy snow? Thw weight dragging the plant down? Usually I rgard rain as a saviour, guaranteeing that the plant temperature will not fall below zero.
"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
“It's still magic even if you know how it's done.”
Frosty and dry does far less damage than frosty/icy after wet.
It's also not as simple as just a period of frost, any more than it's just as simple as a period of strong sun/heat.
It's what happens over longer periods of time. That has a far greater impact on plants.
I live in west central Scotland - not where that photo is...
Wet crowns and leaves that freeze is a death knell to certain tenders that would ordinarily survive a freezing dry period.
I have always regarded water in freezing guaranteed that the temperature would not fall below zero. (Latent Heat and all that.). And most plants can take -1 or 2. One never stops learning.
"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."