Hardy Aloes in the UK garden

[Mike_K]

What is your experience in growing Aloes outdoors. Which Aloe have you already tested and had success with. What minimum temperature it survived without leaf damage?

I grow several Aloe plants in my garden in Devon which I cover with a bubble wrap from November to February to protect from rain and frost. So far I have planted
Aloe striatula, A. juvenna, A. aristata, A. X Spinosissima and
the plants shown no damage when exposed to -2 deg C temperature.

[edds]

I've only got polyphylla outside since 2020 but that seems to be doing well (haven't removed the fleece I chucked over them during the recent cold spell yet though!)

Paul S is your man for an extensive list of what has and hasn't worked so far! I've got some seeds of littoralis to try as well once they're big enough.

[Paul in Essex]

Over what kind of period is this? if your low temp over several years is -2C then you have a lot to choose from.

Plants I have grown here that have been fine at -2C include:
striatula
aristata
'Cosmo'
maculata
polyphylla
brevifolia
plicatilis
x nobilis (perfoliata)
mitriformis
humilis
erinacea
arborescens
mutabilis
broomii
speciosa
x salm-dyckiana
fosteri
greatheadii
grandidentata
reitzii
cooperi
ecklonis
boylei
verrecunda
pratensis (if you find one, get two and let me know)
ciliaris
ferox
spectabilis
'Hercules'

The list that are fine to -5C is substantially smaller

[Aiko]

The list that are fine to -5C is substantially smaller

To be honest, I am not really calling that hardy. Good enough for early spring somewhere in March or early April, when there are nights that could go down this low. But for winter in the long run, hardy up to -5C is not good enough for my (still very mild) winters.

[esp]

What is your experience in growing Aloes outdoors. Which Aloe have you already tested and had success with. What minimum temperature it survived without leaf damage?

I grow several Aloe plants in my garden in Devon which I cover with a bubble wrap from November to February to protect from rain and frost. So far I have planted
Aloe striatula, A. juvenna, A. aristata, A. X Spinosissima and
the plants shown no damage when exposed to -2 deg C temperature.

I've only tried A. aristata and striatula outside all year round.
On of my striatulas has suffered major leaf loss in the cold spell just finished - it was soaking wet and unprotected. Minimum was meant to be about -4C here, they probably went days on end without thawing due to being in a very sunless spot in winter. Another kept a bit dryer seems undamaged.

A. striata seems OK in my unheated greenhouse, also A. ferox and marlothii. What I think is a striata hybrid froze solid in the greenhouse, adopted an ominous translucent appearance and was looking pretty sick, but seems to have totally recovered now, with leaf damage being limited to a bit of drying of leaf tips only.
A couple of slightly damp A. plicatilis seedlings froze solid in the G/h at -4 and died or suffered major damage, a few dryer ones seem OK.

[Paul in Essex]

The list that are fine to -5C is substantially smaller

To be honest, I am not really calling that hardy. Good enough for early spring somewhere in March or early April, when there are nights that could go down this low. But for winter in the long run, hardy up to -5C is not good enough for my (still very mild) winters.

It's what the fellow asked, though, so that's what I listed.
If you want a list of aloes hardy enough for -10C it isn't very long

[Mike_K]

There is a list of hardy Aloes by Brian Kemble that can be found on the internet. I wonder how the minimum temperatures listed there compare to the UK weather conditions. More than a dozen species from the list can withstand the temperature lower than -4 deg C.

[Paul in Essex]

There is a list of hardy Aloes by Brian Kemble that can be found on the internet. I wonder how the minimum temperatures listed there compare to the UK weather conditions. More than a dozen species from the list can withstand the temperature lower than -4 deg C.

That is the big issue, they don't really. It is not so much what happens in winter but what happens in summer. Or, rather, what doesn't. We don't get long hot summers here as a rule. Long hot summers somehow change the cell sap into some kind of anti-freeze and that doesn't happen here.

[edds]

They don't seem to have lots of days sitting in gloomy, wet, low single digit temperatures either. Where a lot of these plants grow it might be -4 overnight but it can also be mid 20 degrees in the same month! I don't imagine they have days below freezing and, if they do, it will be dry. Much more like conditions in our cool greenhouses I would suggest!

[MikeT]

A lot will depend on your particular microclimate. I'm at about 130m above sea level, some parts of Sheffield are maybe only 30 m above sea level. The Botanical Gardens in Sheffield has an Aloe striatula that has survived snow and ice for many years. It's at the top end of the gardens, so something like 130m elevation.

It hasn't looked as good as this in 2022, several stems were chopped back, but there is new growth coming.

I've had Aloe aristata survive several years outdoors in Sheffield, it shrugs off being covered in snow, but in a particularly cold winter it dies. Fine in an unheated greenhouse.

I don't find Aloe juvenna at all hardy, it can survive winter in an unheated greenhouse in Sheffield, but not reliably.

Factors like drainage or protection from a wall may make all the difference between a plant surviving and one a few metres away dying.