Plunge temperature for orchids

[mark smyth]

What temperature have you set plunge heating cables, in sand, for winter green and borderline hardy winter green orchids?

My sand that was 12C last week is now single numbers.

[Peter Maguire]

If they're plunged, I don't heat the plunge. I do have a convector heater for the alpine house that I turn on to try to keep it frost free if the forecast is for below -3C.
Anything that doesn't like this treatment is on the compost heap. 

[Anthony Darby]

Depends on the orchids Mark. If they are Mediterranean it's the air temperature that is also important as the rosettes won't tolerate much, if any, frost. This is their growing time.

[Tony Willis]

I have my cables set at 5c. The beds are covered with a box covered in bubble polythene and the top of this is about 20 cms above the sand. The inside has had ice on it when the outside temp went down to -9c but the plants at soil level did not freeze.

I keep ophrys/orchis cyclamen,massonia and a variety of other tender things in them.

I would say that the cables only seem to come on for a few days each winter. On frost free days I open the frames up for ventilation.

I do not class any of these as alpines or rock plants even though many are accepted in shows but it is a choice to grow some tender plants. I would not want to see them go to the compost heap.

[Peter Maguire]

Tony,

I think you've convinced me. I've been mentally reviewing what I grow/would like to grow and having taken out the soil warming cable a few years ago, I think that I'll be putting them back again, at least in one of the plunge beds, especially after the last two winters, which are more reminiscent of the winters I remember from the 80s.
It will mean a major reorganisation of the plunge beds, but I was planning on doing this anyway.

[mark smyth]

Depends on the orchids Mark. If they are Mediterranean its the air temperature that is also important as the rosettes won't tolerate much, if any, frost. This is their growing time.

Anthony it's a mix of hardy UK and some borderline hardy European ones I foolishly bought. Orchis, Dactylorhiza and one or two Ophrys. All now have rosettes except O. mascula. Maybe it needs a bit more water?

I was thinking of 2 degrees but 5 sounds better.

The electrician is coming next week to wire the green house for electricity. Do you guys have a water proof plug board raised off the ground attached to a window? I need some ideas before he comes.

[mark smyth]

I have my cables set at 5c. The beds are covered with a box covered in bubble polythene and the top of this is about 20 cms above the sand.

I was thinking of asking a joiner to make me a rabbit run shaped cage to go over mine. I'm not good enough with a saw

[Tony Willis]

Mark I am making no comments on my electrics.

You do not need height on any covering because this will negate any warmth coming of the sand and the temperature will be much the same inside it as in the greenhouse.

I think it is too early to be seeing your mascula yet. Mine are not showing and yet the rest all have well developed rosettes. I have been giving mine plenty of water since the start of September.

I am not sure why you are keeping the dactylorhiza frost free.

I have attached two pictures,the first open with the front bubble wrap removed in late spring and the second closed down in the middle of a freezing spell. I have now replaced the bubble wrap with insulating plastic sheet. They are basic cheap and effective.

[mark smyth]

Tony I like the cover. Better than my idea.

I have three Dactylorhizas that I was told to keep frost free - D. romana, D. fuchsii albino and D. cordigera.

[SteveC2]

Romana and cordigera will certainly need protection Mark, at least they would here in Lincolnshire.  I treat my romana exactly like an Ophrys and it's doing fine.  Flowers every year, totally refuses to bulk up though, so might be a subject for your tuber removal operations next spring!  Cannot really see why an albino fuchsii would need any different treatment than the norm though, which would make it hardy as they come.  Of course, rarity and expense might make you want to give it a bit of protection, but that's not always a good idea.

[Peter Maguire]

The electrician is coming next week to wire the green house for electricity. Do you guys have a water proof plug board raised off the ground attached to a window? I need some ideas before he comes.

Mark,
I have a similar setup to Tony as regards the plunge system (don't have the cover yet!). For electrics what I did was to use surface mounted, exterior quality pattress boxes (metal) with a metal double socket which has a built in circuit breaker - they're in a similar position to where he has his controller for the heater cables. there are two double sockets and the electric wires are run along the front of the plunge beds in polypropylene tubing for protection, The same tubing runs from the garage on the opposite side of the house (where the circuit board is), under the patio, then under the path to the greenhouse. Having the wire buried in the polypropylene tube protects it from digging, etc, which it should not be exposed to as it it under other (solid) structures.
I find that four sockets are all I need in the greenhouse - if I need light, then there is a plug which can drop down from strip lights in the roof to be plugged in. This saves having a fancy distribution board with lighting circuits, etc.
I'll post photos later in the week (Friday) if that would help- it tends to be dark when I get home from work now.

[mark smyth]

thanks Peter

[Neil]

All my electric sockets are IP56 rated, which is stops most dust ingress and will take a direct hit from a pressure washer without letting water in.  Also I have used glands on every joint I have used. 

Mark D. romana and cordigera as said before treat them as tender, as I take it you do not know the provenance of the original plants the seed  came from,   however this two species are found round up into Bulgaria and Russia and both can get really cold!

Orchis mascula will not show itself until March for me, but saying that I do have 1 pot that are poking their noses above the surface.

[Peter Maguire]

Mark,
I said that I would post a few pictures of the electrical setup to give you an idea of how I approached the problem. They should be self-explanatory, but in case you were wondering about the cable from the fluorescent light - during the summer and in fact during daylight hours in winter, this is curled up in the roof of the greenhouse. The double lighting tube is mounted on a thin piece of wood which rests across the braces for the roof - there are two cup hooks screwed into it which the cable can be wound around.
The close up shows one of the socket boxes which has a built in RCD: of course there is another RCD on the circuit at the circuit board in the garage, so it's well protected. I also sealed the patress boxes on the inside with silicone sealant around the joint/screw holes when they were fitted.
The wiring up was something I did, but the electrician checked everything before connecting it up to the electric supply - he was quite happy with the way I had arranged the internal electrics is the greenhouse.

[mark smyth]

Gasp - no plugs water proof.

I think I'll have plugs attached to the frames also

and electrify the green house frame. Some smart a$$ last night removed some louvre glass but thanksfully didnt break them. Maybe s/he was disturbed