Hello Davide, your Gymno looks like G. platense.
Your Oroya looks like a typical Oroya seedling, but it also looks like a Matucana, (aureiflora, aurantiaca, or ritteri etc). Of course when it flowers then you'll have a better chance to ID with some certainty.
It's possible too that you little plant in the middle is a melocactus, though I have no idea which species. I have grown Melocacti successfully in glasshouse with winter temps below zero (I kept them quite dry throughout the winter months), so you should be able to grow them okay there, remember also they do best in a humid situation.

Hope this helps. CP

Thanks CP, do you mean I should vaporize water on the Melocactus during winter?

P.S. I have ever thought that all melocacti must have a prominent cephalio on top, is it right?
davide

Where I live the humidity levels during summer are quite low, so I made shallow trays that I filled with small rocks and pebbles, these trays also held some water, (I had drain holes to keep the water level below the level of the rocks). I would then place the pots containing the Melos on top of the rocks in these trays.
The water in the trays raised the humidity levels without keeping their feet wet, as I routinely watered the plants, this would also replenish the reservoir of water in the trays.
As for winter time I kept the whole deal dry, as I didn't want to run the risk of rot.
I managed to have several Melos with beautiful cephaliums, but I lost these and many other plantss when vandals raided my glasshouse.
Melocacti don't produce their cephalium until they reach maturity. Depending on the species, a plant doesn't reach maturity for a number of years, I think my first one took 7 or 8 years, and others were 10-12 years. At the point of maturity, the plant body stops growing, and the bristly cephalium forms and continues to grow, and the flowers appear in the bristles.

I hope I have made this clear enough, and haven't confused you, If your climate already has high humidity levels, then you Melos should thrive anyway.

Thanks CP, you made all very clear, yes we have a very wet climate so no water at all throughout the winter months! I'm sorry for your glasshouse (unfortunately vandals are present in every part of the world)
davide

I don't grow Melocactus but cold and humidity don't mix. They are amongst the least cold-hardy of all the cacti. Humidity in summer should be fine. Avoid frost completely. In England, they are generally kept at a minimum of 10C over winter because they will start to mark at lower temperatures. You may be able to do better with warmer days and lower humidity. They are mostly tropical and appreciate hot humid weather, a few species grow in mountains and handle the cold a bit better.

Hello,

I lost quite some great looking melocacti.
One of them was my favourite cactus but survived only for a period of three years.
{{gwi:476365}}
They are not easy to keep in winter.
In my veranda it is never below 5 degrees but I do not keep my meli there in winter.
Even in winter they should be in an environment where it's
10-15 degrees and they have to be kept humid.
They have to get the maximum of light and sun.

If you are not able to give these conditions,I'm afraid that you will end up like me.
I manage to keep them for a few years but due to the cold
winters,the root system is getting always less and less.
I have more success with melo seedlings that are getting used to the climate conditions here in Belgium.

Greetings,

Hans

I bought my first melocactus this summer and is doing great. Now I am worried. I am keeping it indoors for the winter. My house temp. is at 70F. But is dry. I have the plant in a west window. Am I going to need to provide humidity for this plant? Would I be better off keeping the plant under artificial light. The bulbs I use are called natural sunlight bulbs. I have 2- 40 watt bulbs to a strip light.
Thanks,
Dawn

Hans, thank you for these useful informations, now I am a bit worried about the future of my Melo....I live in Sardinia and our winter wheater generally is pleasant but sometime (10-15 days per year) we have some low temperature (0-5 °C). I think to keep my plant in the greenhouse hoping it could survive!
Greeting
davide

Davide,

Six weeks a year I'm in Toscany and I know that even there it can be quite cold.
It's certainly better then Belgium and you have lots more sun so put it in the sunniest place!
Maybe you could just put a little improvised greenhouse in your glass greenhouse using thick plastic to isolate.

Greetings,

Hans

Dawn, I kept a small M. matanzanus over the winter last year. I had it in a south facing window near my kitchen sink. I misted it occasionally, and watered about once a month. I put some perlite in the bottom of the clay pot, and used C&S soil mixed with perlite. The cephalium developed this summer, and even threw out a few blooms! You might want to put the pot on a tray of pebbles, filled partially with some water to provide extra humidity. HTH

I never knew they were difficult plants when I bought my first melos so apart from providing for their extra humidity requirements, I treated them like any of my other cacti.
If not for the vandals my melos would be well over 20 years old now the oldest ones at the time would have been 16-17 years old and had suvived many a cold winter with dry roots.
My glasshouse is never heated and the eastern end is always open (no door).
Davide just do you best, you'll be pleasantly surprised I'll bet, but if you fail, persevere... try again using different methods. :)

Regards, CP

Hi Davide,

I didn't want to make you worried and found on this forum this link.
http://jp29.org/cecu.htm
I agree with many things they say.
It says:"It is my experience that these plants (especially Discocactus and Melocactus) are intolerant of the combination of cold temperatures, wet soil and dull, overcast skies. "
If you want a description of belgian winters,here you have it.
In Sardegna the climate is much better and sunnier so probably you shouldn't worry.

Greetings,

Hans

It is considered difficult to grow clean unmarked Melocactus and Discocactus in England, but I was looking at some pictures from a trip to Brazil last night and almost every plant was spotless and healthy even in the middle of the dry season.

Thanks Hans and S&B, this winter I'll try to keep my melo in a little plastic greenhouse in south part of my main greenhouse. Next spring I'll post an updated pic of the subject!
Davide