[Grubbypaws]

I planted three healthy looking plants in spring in shade underneath a larch tree. The soil is moist acidic and well drained. The plants however are not thriving. Some stems seem to be turning black and the leaves dying. This is meant to be a thug and I seem to be killing them 

Has anyone any idea what I am doing wrong?

[arugula]

Underneath things is the right way to grow it, I'm wondering if something about the larch is upsetting it..

[Grubbypaws]

That is what I was thinking but they are meant to be OK in acid soils.

Is there any thing different about larch needles from other conifers?

I have cleared some of the needles from the plants and whole stems have just died and gone black. One stem is beginning to turn black for a segment and the leaves at the end are dying.

I was anxious about planting this as I know its reputation but thought it needed a thug to survive there. The oak ferns are doing well in the same spot.

If they simply dont like the conditions I will have to replant something else. Epimediums maybe?

[arugula]

I had it in my mind that the larch might be poisonous to other plants but I've looked this up and apparently it isn't. Hmm.

[mumofstig]

Is the soil under the larch too dry?

[Grubbypaws]

I have no idea why I said Larch  (Either a senior moment or a blonde one; I am in the transition phase )

They are growing under a cedrus diadara. Can you look this one up for me argyllie. I hope they are not poisonous as when I cleared the needles away I put them round my blueberries!

No mumof S it is not dry as I have made a special watering device. I collect water above the 'canopy' and pipe it through to the plants below. It is shady and acidic but moist and well drained.

[arugula]

They are growing under a cedrus diadara. Can you look this one up for me argyllie.

Not poisonous to other plants as far as I can find out.

Looking at possible diseases for Vinca minor, going by the symptoms you report, I wonder if stem blight is a possibility:

Stem Blight

Stem blight is a widespread and potentially fatal disease caused by a fungus (Phoma exigua var. exigua), which persists indefinitely in plant debris and moist soil. Symptoms include quick-growing, dark brown or black lesions that girdle stems at the ground, causing dieback. The lesions may extend over the entire stem in only a few days. Dark spots may appear on leaves, causing them to brown, wither and drop. The plant may die within two or three weeks.

Full article here: http://www.gardenguides.com/100693-vinca-minor-diseases.html

[Grubbypaws]

 
Sounds right. Thank you for your hard work argyllie. I bought them from http://www.plantsforshade.co.uk. They have sent me some very good plants overtime so I will let them know. Sounds like I cannot ever grow them there again. Do you have the ability to find out if Phoma exigua var. exigua affects other plants?

[arugula]

Here is some more info about it:

http://gardener.wikia.com/wiki/Phoma_blight

[Grubbypaws]

One of the host plants is Solanum tuberosum .  . There is about 3 metres between the affected Vinca and my healthy potatoes. Should I be worried? How does this fungus spread?

Damn. I moved some of the needles from around the vinca to my blueberries which are right next to the potatoes 

[Grubbypaws]

Here is some more info about it:

http://gardener.wikia.com/wiki/Phoma_blight

Oh and there is a photo of a pepper as well 

[Grubbypaws]

I have been spraying them with fungicide but to no avail. Anyone out there know if it is treatable or am I best to destroy the plants to contain it?