Petrocosmea problem

[Peter Maguire]

Has anyone experienced a problem with Perocosmeas losing their root system?
I used to have four largish specimens plunged in pots in the alpine house. They came through the winter ok, but the other day I thought that they looked a little poorly. Every one came away in my hand, so I have gone from four showable plants to three trays of leaf cuttings.
I fully expected to find the old enemy, vine weevil grubs, in the pots when I emptied them out and was looking forward to squashing the little b-----s, but there was no sign of anything in the pots. No grubs, no pupae, but no roots either. 
Any suggestions gratefully received.

[Maggi Young]

Peter, if there is no sign of rot or mould on the plants then I'm inclined to think the vine weevils ARE the culprits, but that they have already made their getaway.

[Lesley Cox]

I'd agree with Maggi there as it has happened with Ramondas here. It may be possible to dip the bases of at least some parts of the plants (you may not want to do it with all, but maybe you could divide off pieces) in a rooting hormone (I'd go for a liquid at specified rates) and insert them into a gritty mix as cuttings, not too much, if anything, actually buried.

Having said all this, I have to admit to having been deprived of Petrocosmeas all my life. There are none here as far as I know, but if you don't try, you won't know will you.

[Michael J Campbell]

Lesley,mine set seed and I have a potful of seedlings growing on at the moment so they at fertile. I can save you some if they set seed this Autumn.

[Peter Maguire]

Peter, if there is no sign of rot or mould on the plants then I'm inclined to think the vine weevils ARE the culprits, but that they have already made their getaway.

I'm afraid that I agree Maggi. I rather hoped that someone might have a different answer, as if there are no vine weevils in the Petrocosmea pots because they've matured and walked away - where are they laying their eggs???

[Maggi Young]

where are they laying their eggs???

Usual answer to that is anywhere they jolly well like....

[Lesley Cox]

Lesley,mine set seed and I have a potful of seedlings growing on at the moment so they at fertile. I can save you some if they set seed this Autumn.

Michael, that is a very kind thought, and much appreciated. Unfortunately Petrocosmea does not appear on our Bio Index (permitted list) at all, so we must assume there are no species in NZ and therefore we may not import any, either as seed or plants. Yet another of life's little frustrations.

[Diane Clement]

I'm afraid that I agree Maggi. I rather hoped that someone might have a different answer, as if there are no vine weevils in the Petrocosmea pots because they've matured and walked away - where are they laying their eggs???  

I've had this problem several times and I have wondered why, but I've come round to the conclusion that I don't think it is vine weevils, because I've never found a grub in the pot, whereas I always have in other plants with vine weevil damage.  I wonder if it might be a watering issue.  I've tried to re-root the rosettes but it is difficult so probably easier to start again with leaf cuttings or possible small rosette cuttings.

Lesley,mine set seed and I have a potful of seedlings growing on at the moment so they at fertile. I can save you some if they set seed this Autumn.

 
I've never heard of anyone having viable seed before, so you have done well, Michael.  What species have you germinated?  

[Michael J Campbell]

Here they are Diane,Petrocosmea begonifolia.

[Tony Willis]

I have this problem on a number of the rosette forming ones and like Diane think it is a watering problem in the winter. No sign of vine weevils in the problem pots

[Diane Clement]

Here they are Diane,Petrocosmea begonifolia. 

Brilliant, Michael, well done.  I have this species from Keith Lever, but it hasn't yet flowered for me.  Did you have just one - so is it self fertile?

[Michael J Campbell]

Diane, just one Begonifolia also from Keith lever, but had a few others nearby. Maybe they cross pollinated but I don't think they were all in flower at the same time. It will be interesting to see if they come true.

[Peter Maguire]

I wonder if it might be a watering issue.

That's a definite possiblility Diane. The Petrocsmeas shared a plunge with my Hepaticas, which I started to water more heavily in early February. The Petrocosmeas had been fine before that point, even having the odd flower on over the winter.
I'll try keeping them dryer next winter when the leaf cuttings have taken - they're bound to root, I'm following your advice on the 'Midland diary' blog. 

[fermi de Sousa]

Lesley,mine set seed and I have a potful of seedlings growing on at the moment so they at fertile. I can save you some if they set seed this Autumn.

Michael, that is a very kind thought, and much appreciated. Unfortunately Petrocosmea does not appear on our Bio Index (permitted list) at all, so we must assume there are no species in NZ and therefore we may not import any, either as seed or plants. Yet another of life's little frustrations.

But it is on ours
Do they need heat or can you grow them "cold"?
cheers
fermi

[Michael J Campbell]

I grow mine outside with top cover and shade all summer(With the Hepatica, north facing with no sunshine) and bring them into the shaded side of alpine house in autumn (October) or before that if they start to flower. I don't think they like much heat.