Mindy, I don't have a firm answer for you but I do believe the potted ones could overwinter in your attic. Phormiums can actually tolerate a fair amount of cold temps - many sources will list 15-20F as the dropdead point (actually the foliar damage point - many should be root hardy below this). What they CAN'T handle - and I know this from personal experience :-)) - is wet or damp soil and cold. That combo is the kiss of death!! Keep them on the dry side and they should be OK. If you think your attic drops below this A) you need to insulate and B) try wrapping the pots in bubble wrap and cluster the pots together.

Have no suggestion for the ones inground :-( I fear they will not suurvive in zone 5 or if they do, will look like c**p for most of the season.

You zone-pusher you!! :-))

gg, i was sooo hoping you would chime in on this. thank you. to the attic........

btw,OT, have you discovered the gardenrant or garden professors blogs?

best,
mindy

If you haven't already, stick a min/max thermometer up there and see what your real world temperatures are.

You could also start digging. Pit coldframes are actually fairly common here on the old estates. They are useful for a lot of things. So many things that I don't really remember all the things I've helped haul in and out.

Back in the days when I grew phormium, I used to bring them indoors for the winter. They make very attractive, low-maintenace house plants. Nothing seemed to bother them and they always looked good. I kept them on the dry side, in the brightest light this house can muster.
I'd just dump them outside as soon as weather warmed up in spring.

The only issue with keeping phorms indoors over winter is the likelihood they will develop mealy bugs. Mealy bugs ADORE this plant and they get right down inside where the fronds attach to each other and where they emerge from the soil -- hard to get at to treat. If you can avoid this then yes, inside in bright light but cool temps will work.

Back attcha OT :-) I do like gardenrant and visit on occasion, often when searching for something else and that website turns up. The garden professors not so much.......I have issues with one of their primary bloggers who is entirely too dogmatic for my taste.

nina? i was told that house temps are too warm for them and that's why i lost mine and could not use that option!!??plse tell me about your conditions that worked.
best,
mindy

They need light during the winter? ... don't let my plants hear that, lol. Actually, I had needed to reduce my number of potted plants and the Phormiums had went, though these had most easily overwintered in my basement cold room and without the need for any light whatsoever. I have very long winters and they totally took it all in stride from November until being brought out into the warmth of April. I also had no problems with rot.

Terry

terry, your info is sooo important for me. Plse tell me what 'cold' is in that cellar room, and how often you water them. No natural light but also no artificial lights? did you do brugmansia that way as well?(i do brugs in my no-light cellar but it never gets colder than 50F.)
thank you very much,
mindy

Phormiums ARE evergreen and evergreen plants continue to photosynthesize in winter, albeit much more slowly than during the normal growing season. Keeping the plant in a completely unlighted area will not be very much to its liking -- it causes unnecessary stress. Plus you can lose a lot of the coloring, which does require light to maintain. I guess it would depend a lot on how long the plant was held under these conditions :-)

At my nursery, potted phormiums are held in an unheated (usually) greenhouse during winter. Here they receive as much light as a PNW winter can generate and are ready to go back out for sale as soon as the temperatures moderate in early spring and customers are more prevalent. The greenhouse does get heat if very cold temps are predicted but is kept no more than about 40F. I don't think warmer temps would be an issue, like inside a residence -- it just costs a lot to keep the greenhouse warmer than that :-)

If one can replicate anywhere close to these conditions, your phorms should be fine. But keep an eye out for those mealy bugs!!

gg, maybe this is one of those 'we all wish we knew' type questions, but are mealy bug eggs just AROUND,in soil of plants that have been outdoors, waiting to hatch? and do systemics work on destroying m bugs?

if my phormiums are isolated in an attic with no other plants, would mealy bugs find them otherwise?

oh, you'll get a kick out of this. i often and facetiously use a verbal expression to show sincere reverance for a hero of mine >> "genuflect, genuflect". well, hey, girl, take a look at the first two letters of that expression!!!
need i say more?
best,
mindy

Mindy, I have no idea where mealybugs come from......I suspect some sort of spontaneous generation :-) Seriously, they just seem to appear, often under the best of conditions. Lucky phormiums even sport their very own species of mealybug, Balanococcus diminutus (and isn't that a mouthful?!). I find Neem oil to be quite good as a control measure but I'm sure some sort of systemic would work also.

But maybe this is a pest that is more related to milder phormium growing climates and won't be an issue for you. I really have no idea but even phorms growing inground here can be infested with these creatures although they are far more common in containerized plants. I spend hours grooming potted phorms at the nursery, removing affected foliage and spraying.

Here is a link that might be useful: phormium mealybugs

gg, i didn't even get a chuckle out of you?
mindy

Hi Mindy,

I had kept my plants at 34 to 38 F ... watered twice or so during the winter and again receiving no supplemental lighting. Never had I noticed any fading or major dieback or injury ... okay, maybe to the ends of older leaves, but that's pretty much to be expected ... and remember, I'm in zone 3 where winters are very long and plants had needed to stay in storage for 5 to 5 1/2 months ... did I say winters are toooo long here! I had not gotten rid of the Phormiums due to any difficulties or challenges to growing the potted specimens, but rather to the vast amount of work needing to be accomplished on my acreage, it was just time to cut back in that aspect.

Mindy, I'd be a bit concerned about the attic, is it all open rafters, or? ... obviously, zone 5 can experience some rather bitter cold snaps, I'd hate for temperatures to plummet and your plants be severely damaged or lost.

I also had battled mealy bugs, my plants had arrived with them :(

Terry

well now, terry, this is terrific news i think.it definitely counters gg's take on it, but there is nothing like someone's actual experience in a given situation. it is sooo strange, though, isn't it gg? 5.5 mos of total darkness and no leaf damage. weird!

maybe i'll move one of mine to a different unheated attic area that is more insulated but totally dark- and see what happens.
thanks so much for your info,
mindy

Plants never fail to amaze me with their ability to adapt to unfavorable circumstances, so maybe this is just another case in point. I've never tried keeping an evergreen plant without light for an extended period of time simply because of all the cautions one reads about doing so. But..........needs must is always a governing factor, so if that is the only alternative, as with twrosz, I'd say go for it! And report back in spring :-)

Was I supposed to genuflect?? I have bad knees.........lol!

Mindy, gardengal obviously has much experience with these plants and also stated about the importance of cool temperatures. I think the near freezing temps I had provided really assisted them to come through with flying colors. I have also stored other broadleaf evergreen without any problem whatsoever.

Give them a try under a couple of different conditions and see what works best for you ... what was fine for me might not be so fantastic for yourself. Too bad I had not kept my plants and would have been able to provide picture proof :)

gg,no, no, you silly; that's ME doing the genuflecting while thinking of you! :))

two, your help is just terrif.I LOVE desperate measures that succeed (i just finished re-watching Despereaux; can you tell?!)Ah, the Bravery and Fortitude of the remarkable female race! I shall try it and report back.
best,
mindy

Phormium tenax is usually naturally found in lowland and swampy areas perching on hummocks. Has very stiff and upright leaves to about 10', though some of the purple cultivars are definitely lax. Dark red flowers and seed pods. Will easily take moderate frosts down to about -8C. Usually grows out in the open, in full Kiwi sun. (High UV.) Summer temps usually around 20-30C.

Phormium cookianum/colensoi is often found on hillsides up to about 1200m and in well-drained gullies. It has more floppy leaves, yellow flowers and brown twisted seed pods. Easily takes frosts and some snowfall, though not lasting. More of a bush-edge plant but also ok with being open, though it may not grow as tall.

Both tolerate droughty spells. And frequent winter rains.
Both have a very tough covering on the leaves, though they will fray if they suffer a lot of wind. Hardy by the sea.

Possible over-wintering - cheat and remove a young fan from the rhizome. Trim it as you would a bearded iris - with the young growing tip being in the middle and the longest. Plant up in a gritty but moisture-holding brew so the roots will develop well. (If your summers are brutal - pot them on to something more moisture retentive.) That's insurance against disaster.

If there aren't many pots then the inground proposal seems good - plus traditional hay bales around the edges and a thick cover of ag plastic, bubble wrap, fleece, old blankets - whatever is suitable for your area.

When you bring them back for spring-summer harden off carefully so that leaf 'wax' can rebuild because that is what provides a lot of the hardiness.

Mealy bugs. I would suspect deep droughting in the container or the lack of water-holding in the mix. Good drainage, yes, but not the sort of miserable mix that pretends to be wet on top while holding the lower reaches from rewetting. A possible solution (for some) may be the addition of pumice pieces of about 5mm to the mix. And repotting every one to two years, or adding a good organic mulch. They have extensive root systems and will quite quickly fill a container.

Great info I have found here. Old but great. Gonna try to overwinter my Phormiums in darkness since I've no bright room to keep them in winter/

Saw this thread bumped. FWIW Sean Hogan's 'Lake Te Anu' "selected for cold hardiness" P. tenax form survived winter 2013-2014 and 2014-2015 around here. Which were quite cold. Admitted, I did cheat, during some of the freezes, I piled snow on them with my FEL. In other freezes they just had the snow cover that was there. Even with snowcover though, the ground was frozen rock solid. Quite a few tender plants died or were injured. Many Eucomis, for example, lost their main bulb only to survive by offsets. A massive rosemary 'Hill Hardy', maybe 4'X6'X5' with a 5 inch thick trunk, died outright. Couldn't even come back from the roots! In this admittedly milder winter we were down to the the upper single digits probably, and I didn't protect them. They did not have snow cover this time. Much to my surprise they look totally fine at the moment. Point being, this form probably is a little hardier. Of course they are green; variegation weakens the fancy ones to the point they can barely survive the summers here, much less the winters.

In one of my former gardens I had the "heat resistant" strain selected years ago by either Weird Dude's Plant Zoo or Plant Delights, and it was totally killed to the ground by 3F but did recover, albeit very slowly. The aforementioned high elevation strain once offered by Cistus has never had the tops completely die, but they are definitely stunted by the climate and I'm hoping for a lucky run of 2 or 3 mild winters for any chance of seeing them bloom.

In theory you'd expect P. cookianum to be a little hardier but that hasn't been the case in this climate: if anything they seem less heat resistant which means they go into winter weakened and thus die more quickly.

I need Phormium zone 5 hardy

I have 14 varieties in pots. I know there is no chance to overwinter them outside.

If only I had lots lots of money I could talk to e.g. Monsanto to 'make' hardy Phormiums for me.

Don't hold your breath. Monsanto has so many other things on their agenda to dominate world agriculture through genetic engineering that ornamental plants, where the ROI is pitifully small, will never happen. At least in our lifetime. I actually know someone who was once involved in a project with a wholesale nursery company to make hardier plants by gene splicing. Supposedly, just identifying the candidate gene, which was in a spruce, burned up over $250K. That was just the tip of the iceberg. They had hoped to move this gene to, say, Trachycarpus palms to make them a bit hardier. Needless to say once the recession hit the project was shelved for good.