Euphorbia Miners merlot failing

I researched carefully and bought three of these plants and I think have treated them right, planted them in the right place. One is completely fine for now. Two of them are pale and dropping leaves. When the first one started to look ill I dug it up and put in a pot in the greenhouse to nurse it a bit over winter but now a second one is looking pretty bad as well. Any thoughts?

 

Just wondering, how much water have you given them ? What was the soil like around the one you dug up ?

 

I'm not familiar with this variety at all @adamadamant , but I'm not sure putting it in a greenhouse is a good idea. I had a look and it's very hardy, just like pretty much every Euphorbia available.
I agree with @AnniD - have you watered them well since planting?
If you're in a drier part of the country, it's really important to water thoroughly until established. Euphorbias can manage drier conditions, but not when they're newly planted, especially if that's during summer, and in a dry area. In wetter/cooler areas, it's quite easy in summer to get new plants established.
What size were they when you got them? That also has an impact on how well they manage early on. A small plant can struggle, even when planted in a decent site and with good growing conditions. If they were pot bound, that's also a factor if the roots can't get out properly.
Any extra info you can give will help

 

They were only in 9cm pots. I've been watering them in dry spells because they are quite new to the corner they are in. We've had decent rain recently and I don't think the soil was too dry - I'll go and check now.
Yep! Dry! My fault.
Will they recover over the winter? I have them in the greenhouse as I said but it's unheated, so I thought they would be fine. Should I get them out and leave them in a pot in the open air do you think? Grateful for advice

 

HI @adamadamant - I'd keep them outside, but in a sheltered site where they won't get annihilated by weather, but also won't dry out easily. Possibly good to have them quite near your house if possible, so that you can see them easily and water if needed, or just generally check on them.
I often stick small plants in among other planting so that they get acclimatised - especially if I've bought them from a supplier in the south, and at this time of year, so that they get used to my conditions without the stress of being planted out right away. That gives them protection without cossetting them too much. I also have some little perspex tables [they were part of a nest of tables] and I use them a bit like a cold frame, to give very basic protection from our weather here, but without giving them too much help.
If they were only that size, it's because they're basically just cuttings from last year or so, and it would probably have been better to grow them on over winter and plant out next year.
However, they should recover if you just keep them ticking over just now. If they start to thrive again, you might even be able to pot them on, which would be safer than trying to replant. Then you can plant out in spring when conditions are suitable, and you see new growth coming away.

 

Great response all (fairygirl I think I remember you from the BBC site?!) and I hadnt thought about introducing some grit at the roots - I will do that.
Massive thank you to everyone

 

You don't really need grit @adamadamant, unless you're using compost that isn't draining well, but it won't do any harm. I know a lot of compost nowadays is poor in terms of drainage. Better to mix it with your soil/compost mix though.
A photo of your plants would have been good too. It always helps if we can see them - otherwise it can be difficult to tell if there's something more serious going on. We're having to guess a fair bit, and generalise.

Yes - I was on the G'sW site for many years.