You’ve probably always heard that hostas are shade-loving plants, so the following tip is going to sound like heresy, but … if you want to get a young hosta, say a division from a larger plant or a small specimen of a large variety you’ve manage to buy on the cheap, to bulk up as quickly as possible, give it sun. Yes, six hours of sun a day if you can, most of it in the morning. Even full sun all day if you live in a cooler climate!
Do this in early spring as the leaves emerge or else in fall, when the growing season is over. In other words, at the time of year when you usually divide hostas. Don’t move a hosta division from deep shade to full sun in midsummer or all the foliage might burn off. (That won’t kill the plant, but it’s counterproductive, as it will slow the plant down while our goal is to speed it up.)
Sun Effects
Bright sun may cause the leaves to bleach a bit and burnt patches to appear while blue hostas may lose the whitish bloom that gives them their color, but remember this is temporary. These damages only appear on the growth of the current year; the plant’s genetic traits won’t be altered. What the extra sun will do is to allow the leaves to absorb more energy and thus stimulate faster growth, as fast as that particular cultivar can handle (some hostas are naturally slower growers than others).
Of course, you can also plant young hostas in rich soil and keep them well watered. That too will help bulk them up.
Moving to Their New Home
When the hosta does reach the size you want, dig it up and move it to the deep shade if you want to (although hostas really are happiest in partial shade, not than anyone ever tells you that). It will hold its full size, even in soil filled with tree roots (i.e. dry shade), for years and years. But you do need to “plump up” young hostas first if you want to see them reach their full size within your lifetime.
Even here is our semi-arid climate, where we do not grow many hostas at all, we do not thin of them as ‘shade-loving’. They are considered more to be ‘shade-tolerant’. I think if I moved one from a shady spot to a more exposed spot, I would expect it to roast at first, just because that it to be expected, at least it is expected here.