Cypripedium suspended animation

[Alex]

A quick question: I have a couple of Cyps which have grown very nice shoots at the beginning of the season and then, just as the shoots break through the surface of the compost, they stop and don't progress any further. However, they don't rot but remain healthy. This year it's happening with a C. Bardolphianum which came from Hengduan last year....the shoot is very healthy, as are the roots, but it still sits at soil level. Has anyone seen this? Is it a response to high temps perhaps or something else?

Thanks for any insights

Alex

[Alex]

Nobody else seen this?

[Maggi Young]

Not growing enough Cyps to have spotted this , Alex.

[Steve Garvie]

How do you over-winter your Cyps Alex?
I haven't experienced this problem myself but I gather that it can occur in plants which haven't been kept cold enough for long enough in dormancy. What other species have been affected?

[johnw]

Steve/Alex  -  I've seen this long ago and assumed either the conditions in the cool house were, as you say, too warm in winter or the medium was insuffuciently innoculated with the proper myccorhiza.

Thoughts?

john

[Alex]

Thanks all - I over winter in a greenhouse which is nominally kept frost free, but really doesn't drop much below about 5C. it can also get quite warm in early Spring, so I guess it could be the duration of the Winter period as much as the average temps.

This is along the lines of what i was thinking, so I guess I'll have to find somewhere else to overwinter. Where do you all overwinter your Cyps, especially those that grow a lot of Chinese species?

Cheers,

Alex

[Steve Garvie]

I may be wildly off the mark but I feel that this is a thermal trigger issue. Whilst the mycorrhizal relationship is an absolute prerequisite for germination and seedling development in natural systems (and may continue with many/most Cyps ino maturity) I don't think it is relevant in growing cultivated adult Cyps in the non-organic media used nowadays. I am sure that these media recipes are effective simply because they are hostile to microbes and tip the balance of power between the cultivated orchid and its symbiotic root fungi (if present) strongly in favour of the plant. I think it is the presence of mycorrhizae in wild Cyps that makes it so difficult to cultivate such plants -they effectively rot from within.

[Steve Garvie]

I no longer over-winter my Cyps in the greenhouse. Even with the door and all side vents open, a bright sunny wind-less mid-winter day will temporarily raise temperatures above 10șC. When this is repeated on multiple occasions throughout dormancy it must surely have an impact on the dormancy process and the triggers that break it.
My potted cyps are all plunged in an outside raised sandbed with a polycarbonate roof. The bed is behind a north-facing solid fence and gets no direct winter sun. The plunge is in direct contact with the ground. The raised bed, whilst made of timber is lined with 5cm thick polystyrene sheets -this and the volume of damp sand provide a thermal inertia so that temperatures drop slowly over the late autumn but then tend to remain fairly cold and stable over winter. As we can experience severe and at times prolonged frosts in some winters I have installed a heating element in the plunge bed which is thermostatically controlled -activating when the plunge temperature drops below 0șC. Even the hardiest cyps do not survive being frozen solid in a pot!
Prior to this I over-wintered my cyps in a large stone-built garage which was insulated. This worked well with the average winter temperatures hovering around 4-6șC (also good for pleiones).

Cyp. raised bed:

[Catwheazle]

How steve Garvie has written. The plants need a "real" consequent, rather dry winter. The Cypripedium lichiangense is rain-protected in my free-range, has even been able to cope with long-term freezing of several weeks under -25 ° C. What I have observed (with C. debile and C. micranthum): These plants I have in pots because of their smallness. If they are too warm in the morning or winter garden, they stop growing, can even begin feeding too early. They will come back next year, but weakened. I have now put them in the open field, pots into the bed. In the winter they are in the shaded early-morning box at 0 ° C to -5 ° C

[Alex]

Thanks very much, Steve. That looks like a great setup. They are all plunged in sand? It's not completely clear from the photo.

I think your temperature suggestion is most likely correct, so I will have to see what alternative accommodations I can come up with. Your Cyps in that picture look great in growth, whereas a good number of mine are already showing signs of heat damage.

I need a cold frame!

Cheers,

Alex

[Steve Garvie]

Yes, all plunged in sand Alex. There is a drip irrigation system in place to keep the sand plunge moist. I recently installed a couple of small fans to encourage air movement on still wet days.
Despite the above I still experience some losses -mainly due to rot that starts in the sheath left after the new growth buds erupt. This can manifest after a good few weeks of growth and presents as collapse of an apparently healthy shoot which on inspection has rotted just above its attachment to the rhizome. I have convinced myself that this can be prevented if the the rhizome and emerging shoots can be kept dry. I am planning to try out a couple of types of special aggregates (that are normally used to produce specialised concrete mixes) as top dressings. They are inert but have hydroscopic properties (one is made from waste glass and the other is a type of baked clay pellet which has a waterproof vitrefied coating).

[sjusovare]

It's interresting steve, I actually have this issue with epipactises and pleiones, and the issue doesnt seem to be wetness unfortunately since it occured both on rather wet or dry plants.
I came to the conclusion that there is a heavy charge of phytosphthora spores in my environment just waiting to attack the shoots at the slightest watering, but I can't pinpoint the source of contamination, and both natural and chemical fongicides show no effect