Campanula hybridisation

[Lawrence]

I am interested in trying to hybridise some of my Campanulas, particularly the strain of C. betulifolia I grow. Whilst I was probably taught about hybridisation 30 odd years ago my practical knowledge is somewhat limited and so is my terminology, so please forgive me:
I presume I emasculate the flower when in bud form to prevent self pollination, at this point the pistol is straight and the stigma has not split into three at which point do I transfer pollen?. Is the pistol receptive to pollen when a single " stem" before the stigma splits into three or do I apply pollen once the the stigma has split?
Apologies for my ignorance 😳

[Diane Whitehead]

From Flower and Vegetable Plant Breeding by Leslie Watts:

Anthers and stigmas appear very similar to one another at the time when emasculation should be practised i.e. in the young bud stage when flower colour is becoming recognizable, and great care must be exercised.  The three stigmas on the top of the style tend to intermingle with the similarly coloured anthers and are vertical in the bud stage, later opening out and becoming receptive.  Anthers tend to resist being detached, but if one of the stigmas is pulled by mistake the extra resistance makes the error quite obvious.  Cross-pollinations should be made as the flower reaches the opening stage.

Good luck, and please let us know your results.

[Lawrence]

Thanks Diane that's very helpful 👍

[hamparstum]

Lawrence, although I've not tried specifically C.bellidifolia my general criterion is that stigmas become sticky when they are receptive. Common sense would indicate that the stigma will be receptive only after it opened into three parts. The open side of the stigma exudes a thin gluey exudate that holds fast the pollen and induces the generation of the pollen tube ( like a minute fine hair) . On the end of the pollen tube one finds the nuclei that will penetrate the ovum in the receptive ovary. So most vascular plants have this general mechanism. I say most because, nature can surprise even the most knowledgeable and I'm far from that crowd...
Depending on the type of pollination any given species has, anthers and stigmas will mature at differing times within an opening flower. If C. bellidifolia is a natural cross pollinator then they will mature a few days apart. If it is a self pollinator then it will mature at the same time. If yours belongs to this second type you will need to emasculate anthers whilst immature while waiting for the stigma to generate the sticky surface.
Arturo