Smivies -- it's hovering around the -1C mark at the moment, but it's set to get colder than that. So do you think if it goes under -5C, we should bring him in?

Fleece should do it. Bring the pot up close to the house in a sheltered spot. I've just put a couple of these into each of my window boxes and I am intending to leave them out to fend for themselves. The RHS says they are hardy throughout most of the UK down to -5. We rarely go that low. We'll see.

P.S. I think that even if your temperature dips to -5 it's unlikely to stay down that low for long. The problem with pots in places with consistently low winter temps is that the soil in pots freezes and destroys roots. That's never happened in my garden although I have had pots crack. But that was water in the terracotta freezing, not the soil.

its not a houseplant .... and you will have a hard time ...

do you have a barn or storage shed??? .. why not in the outbuilding ...

how big is it.. and how big is the pot ...

ken

Floral – thank you, that's what we'll do!

Ken – the outbuilding is in a bad way on the inside: it's
very damp with so much mould that I wouldn't make my worst enemy spend the
winter in there. We have a very sheltered spot right next to our house, and as
he's only 26" tall, and the pot itself is 10" (and 32.5" at its
widest point), he won't take up a lot of room, so I think that's probably the
best place for him.

it's
very damp with so much mould that I wouldn't make my worst enemy spend the
winter in there.

==>>> ITS A TREE ... it will not care ... never make your plants into people.. i often say.. they are plants.. not children ... because.. once you do .... you assign too many presumptions to the plant ....

in my cold z5 ... the attached garage is at least a z7 ... and the barn is at least a z6 ..

they warm a bit in the sun/day ... retain the heat at night ... remove winter wind ... and moderate the pot in regard to moisture.. wind.. and sun ...

a 10 inch pot.. for a 26 inch tree is rather small ... and subject to wild fluctuations in winter ... i might pot it into a 10 or 15 gallon [big pot] ... to protect the smaller from the variables above ...

your spelling of mould ... make me wonder where you are ... if GB ... what flora says ... otherwise.. if you ever come back.. make sure to tell us where you are ... its very important in this type of issue ...

ken

Ken, the OP said "We live in the north of England, ...." It's dipping to -5c i.e. 23f. T-shirt weather for you ;-)

The tree will be fine outside with a little fleece in cold spells. The soil is unlikely to get very cold unless the temperature stays down for several days (unlikely) and will not fluctuate much.

But Bella, Ken is right that the tree couldn't give two hoots about the mould. However, it will not like the lack of light. You could stick it in there if a night promises to be really cold. But personally I wouldn't bother.

Floral & Ken – thank you, it's good to know that the
mould won't affect him. I do appreciate that you shouldn't treat plants as
children, etc., etc., but a) it's far too late for that, and b) it's not that
I'm concerned he wouldn't "like" the outbuilding, I was afraid it
might damage him in some way. We don't even store furniture or boxes in there
anymore in case they rot, and we certainly don't humanise our furniture! Not
most of the time, anyway…either way, if he's all right to go in there if it
gets very cold, that's good to know.

Floral, you suggested we should bring the pot up close to
the house in a sheltered spot. We've done so, but it's just occurred to me that
this sheltered spot has a large stone arch above it stopping everything
underneath it getting wet. Therefore, in this sheltered spot, rain can't reach
our tree – will that be okay, or should I put him in a spot where he has access
to rain? I've heard that you shouldn't water or feed trees over winter, but if he
has no access to rain, will he need watering?

Bella - you're wildly over-thinking this. Just shove it (not he) out a bit to where it can get the rain. And while boxes and furniture can go mouldy your growing tree will not. These things are cheap and easily replaceable. You could get a new one for under 6 quid.

Actually excessive humidity in combination with low temperatures during winter inside greenhouses causing plants to mold and collapse is something that happens.

If it were mine I would stick the potted cypress somewhere that doesn't freeze before hard frost occurs. Here I place suspect plants near a south-facing window inside my garage during the cold months.

Testing has shown an approximate 20F differential between hardiness of plants in the ground and hardiness of the same kinds in containers. The first thing to go is the new roots out near the pot walls, followed by the old roots farther back, and then the top. So potted plants left out to freeze can appear undamaged when actually a portion of the roots have been killed.

The OP has an outbuilding, not a greenhouse, and the idea would be just to put the plant in there overnight if the temperature was likely to dip below -5. Obviously it would not be kept in there long since it would be far too dark. Mould is not going to be a problem on a conifer kept under cover overnight.

This plant is widely used as Winter container filler. It is common, cheap, easy to grow and perfectly capable of surviving a winter in a pot outdoors in most of England, possibly with a little fleece on nights likely to dip below -5c. The OP is in Northern England but we don't know where. It is probable that their Winter nights are colder than mine but not that much. Where I am the average lowest temp for January is -1, around 30f. Pots rarely freeze.

I do not claim to know anything of growing conditions in USDA 8 Sunset 5 WA but I suspect I have gardened through a few more more English Winters than some.

The cypresses have become common here also.

Embothrium, floral, and Ken – thank you all so much for your
help.

Even I have one. ;-)

Mike

Where it is different from Britain here is there are very few examples of these of any serious age and size. Even the typical green parental tree is quite rare - although somewhat incongruously, large examples do exist here - so there is not an environmental condition that excludes the species entirely. Whereas the green ones in particular are ubiquitous south of here, in northern California coastal communities.

Brown patches often appear on the recently planted yellow forms here. Recently I noticed that the browning of one near me was on the north side, implying winter injury. Otherwise last summer was hot (yellow foliage variants of conifers are often prone to sun damage), and the species is limited to outer coastal areas in the wild by disease pressure.

Another yellow one I used to drive regularly got maybe as much as 8'-10' tall - and then fell open under a snow load, was cut down. An 'Aurea'? 'Donard Gold'? more than 24' tall (ca 2005) in Seattle (USDA 8) is quite exceptional for this area, the only other anywhere near comparable example reported (2006) from there being a 20' (ca 2005) 'Fine Gold' that was planted 1999 or earlier.