It'll grow but not well.....what is generally a rather unkempt and scraggly-looking shrub (without pruning) will be even more leggy and scraggly-looking and produce few flowers. This is really a shrub for full sun - as it often tends to be challenged by our winter weather, why not provide it the best possible conditions from the outset? There are so many other shrubs to select from that will tolerate or even thrive in shadier conditions.

I have one in a very shady corner, under an arbutus and against a wall.... it is thriving and I constantly have to hack it back as it tries to choke everything surrounding it. Have now pruned it to a tall, narrow cylinder and it seems happy. Give it a try.

Somebody else might look at that one and see the effects of the shading, point out how it wasn't actually thriving in the usual sense. Escallonia are hot sun shrubs, at least in this region.

The commonly sold Apple blossom escallonia of outlets here is correctly 'Donard Seedling'. The cultivar 'Appleblossom' is different, more like a Pink Princess = 'Frades' but with the apple blossom flower coloring instead. They had some of this at the Seattle arboretum but it froze down in a hard winter, and I don't think came back. You can see sprigs of 'Donard Seedling' and 'Appleblossom' right next to each other on the appropriate page of the Phillips & Rix Shrubs book.

'Donard Radiance' is a striking one that has been seen in local garden centers in recent years. Alternative sources like Colvos Creek nursery offer additional selections not seen in the general trade.

I have three on a north wall and they grow well but they never flower as much as the ones that are 10' away and in more sun. I cut them back hard this Feb and by the middle of the summer they were completely grown in.
Bees love them..........

Shrubs that can't survive a range of conditions can't survive much. Most commonly sold ornamentals are comparatively forgiving. But they all have an optimum set of circumstances, which when experienced they have their best appearance.

During hard winters shaded specimens of broadleaf evergreens may come through intact while others, growing nearby but exposed to the sun may burn down to the snow line or ground level. But the rest of the time the shaded ones will be showing the effects of being shaded, with sun-loving plants these could include gaunt habit and reduced flowering.

I was thinking of 'Pride of Donard' when I typed 'Donard Radiance'.