What to do about frost?
bédé
Posts: 3,095
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.
"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
Posts
Plants such as Phormiums were rarely seen due to their lack of hardiness and some that are sold in garden centres now need to be under glass in the winter here. P Blondie and P Platt's Black sell on sight but need to come inside . I did purchase P Blondie two years ago but returned it when I realised. The response at the GC was 'needs to be under glass in winter'. Nothing to let the buyer Know.
Ceonothus were all but wiped out in a cold winter some years ago.
One thing they all have in common is they originate from the Southern Hemisphere.
The GC's will be selling them again this summer and gardeners will continue to buy them.
With more recent winter being warmer gardeners have' pushed the boundries' with plants like woody Salvias and Nemisias. At some point a cold winter was inevitable.
Some of my early Rhododendrons have flowers that are hardy in bud, but not in flower. They come as a flush so that after a frost, everything is lost.
My Camellias normally flower over a long period. If they are cut by frost the repeats survive.
Young shoots are also more vulnerable, perhaps that's obvious. My beech hedge, almost 1 year in 2, gets it;s young growth cut by ground frosts in late May, even June. It recovers and it saves me trimming the top until later in the year.
"Have nothing in your garden that you don't know to be useful, or believe to be beautiful."
In the sticks near Peterborough
It is extremely worrying how little rain we've had so far in 2023. The good rainfall in Nov and Dec won't have been nearly enough to replenish ground water reserves and my soil is already so dry that I'm delaying mulching until we've either had a good downpour or I've bitten the bullet and given it a good watering.
In the sticks near Peterborough
I am no expert on plant labels but they display less information than years ago, I assume to fit with EU regulations?
@nutcutlet Yes I agree. I think a dry hot summer followed by a spell of wet weather that saturated the ground and then deep cold frosts have damaged plants at the roots.
With more cold weather expected here in the Midlands the ground is dry which may be helpful for some vunerable plants.