I have a brand new 6x10 greenhouse with staging in my garden that is currently empty as I'm too scared/confused to put plants in there. So my cactus collection remains scattered around my house. The GH is unheated and OH has hurt his shoulder so I don't think I can get anything wired in this spring.
What if any plants can I move into my GH?
Is there a comprehensive list of minimum temperatures for each species?
The internet is throwing up such a wide variety of answers that I feel like I'm getting no where.
The long term weather forecast shows that there's likely to be frosts well in to April so at this rate I won't be able to use my GH until May/June! Seems such a waste as I was so excited to get one
Please can anyone help?
Off the top of my head, my plants include:
Echeverias
Aeoniums
Agave
Aloe
Haworthia
Trichocereous
Golden Barrel
Lithops
Ferocactus
Don't worry. They can take some frost. Maybe be a bit more careful with the Aeoniums. If there will be frost, just bring them indoors for a night.
All others are hardy, some even very hardy. Lithops you can safely keep unprotected from the cold the entire winter. All of mine survived last winter, in the greenhouse without protection.
I'd agree with Aiko - although some species (e.g. most Aeoniums and Haworthias) are "tender", they should be fine with a degree or 2 of frost if dry. The inside of your greenhouse should be a degree or 2 warmer than outdoors anyway.
Many Trichocereus, Echeverias and Agaves are very hardy, -6 or so should be fine for them if dry. Some Agaves are extremely cold resistant, unlikely to be harmed by any Sheffield temps if dry. The repeated use of "if dry" is quite important!
Echinocactus grusonii has a reputation for marking badly if cold, the same for some Ferocacti, but there's a big difference between -0.5 deg for a few hours in late March and -5.5 deg minimum and never above freezing for 3 days solid in January.
Specks Exotica, not in business anymore, still has a list of cultivation guidelines including minium temperatures. See: http://www.specks-exotica.com/en/cultivation_data.html. But this list is almost totally dedicated to Pachycaul succulents. Definately no cacti or mesembs on this list, but there are some Agaves on there. The don't show anything lower tan 6C, but count on them to easily cope with 0C...
Echinocactus grusonii tends to mark with cold (or cold and damp, but then cold in the Hope Valley will also be damp), as has been mentioned. I don't find Ferocacti quite as prone to this, but it can happen some years in an unheated greenhouse. The others you mentioned will be fine most years without any heat, but in an exceptionally cold year there would be losses. I would advise getting an electric supply, it gives that protection on the odd occasion it's needed. It also means that you can have a fan running. I find Espostoas, Haageocerei, Californian Mammillarias, Pachypodiums, and Brazilian cacti are likely to suffer if the temperature goes down to freezing. Most others are fine. Many books and on-line sources quote minimum temperatures that are way above what the plants will cope with perfectly happily. Cleistocacti I find will take the low temperature, but the growing tips can dry out, so I prefer to give a little extra warmth and then I can safely give a little water some weeks earlier than I water the greenhouse plants.
Do ventilate the greenhouse when you can in winter. Botrytis can affect Echeverias, Aeoniums, or any plant with dead flower remains, the best preventive measure (as well as removing dead leaves and flower remains) is good ventilation. I open my greenhouse door most days in winter; this winter it's been deliberately left open at night quite often. The fan runs continuously.
MikeT wrote: ↑Tue Mar 12, 2019 1:58 pm
Echinocactus grusonii tends to mark with cold (or cold and damp, but then cold in the Hope Valley will also be damp), as has been mentioned. I don't find Ferocacti quite as prone to this, but it can happen some years in an unheated greenhouse. The others you mentioned will be fine most years without any heat, but in an exceptionally cold year there would be losses. I would advise getting an electric supply, it gives that protection on the odd occasion it's needed. It also means that you can have a fan running. I find Espostoas, Haageocerei, Californian Mammillarias, Pachypodiums, and Brazilian cacti are likely to suffer if the temperature goes down to freezing. Most others are fine. Many books and on-line sources quote minimum temperatures that are way above what the plants will cope with perfectly happily. Cleistocacti I find will take the low temperature, but the growing tips can dry out, so I prefer to give a little extra warmth and then I can safely give a little water some weeks earlier than I water the greenhouse plants.
Do ventilate the greenhouse when you can in winter. Botrytis can affect Echeverias, Aeoniums, or any plant with dead flower remains, the best preventive measure (as well as removing dead leaves and flower remains) is good ventilation. I open my greenhouse door most days in winter; this winter it's been deliberately left open at night quite often. The fan runs continuously.
Thanks Mike
What do you think about the tenderness of euphorbia and myrtillocactus? I have some that are really too big to live in the conservatory much longer.
aloedanielo wrote: ↑Tue Mar 12, 2019 2:18 pm
What do you think about the tenderness of euphorbia and myrtillocactus? I have some that are really too big to live in the conservatory much longer.
Some Euphorbias will take down to freezing. Resinifera and mammillaris have coped with this for me. There aren't many others I'd feel confident about. Obesa might, but is safer kept above freezing. Canariensis won't take freezing. Most of my limited collection of Euphorbias are overwintered in the loft, not the greenhouse.
Myrtillocactus I haven't grown, I have an idea that it prefers warmer winter temperature - maybe someone who grows it could comment?
If Mrytillocactus and Euphorbias are too large, I'd consider beheading - root the top, and get offsets from the base. Then you have a different problem, finding someone to take the new plants - though you should be able to sell them.
I'll start moving them out to the GH then. I've got loads of fleece on standby if it goes too cold again.