Hostas are very often mistaken as ideal plants for deep shade. Although it is correct that hostas are shade plants, they still benefit from a good level of light and deep shade is not the perfect conditions for them. You will very often find that a hosta grown in deep shade is half the size as one planted at the same time in full sun. In terms of shade, simply avoiding the direct midday sun can be enough to have perfect hostas for the growing season.
One mistake that a lot of people make is planting directly under mature trees...'hostas are woodland plants, that's the perfect spot'...unfortunately this is rarely the case. Planting hostas under mature trees is usually a sure fire way of have sickly looking stunted hostas. Having to compete with the roots of the trees makes life very tricky for freshly planted hostas. We will regularly ask our customers 'what else grows under this tree' and very often the answer is 'nothing, not even weeds', chances are that a hosta isn't going to be the exception. We would recommend that you plant away from the main roots of the tree where the ground has more moisture and nutrient.
There are however some excellent varieties that will look at their best when given a shadier spot. As a general rule the blue varieties benefit more from deep shade and the more yellow varieties benefit more from a bit of sun. We would recommend planting strong reliable blue varieties in deep shade to have the best chance. Varieties such a sieboldiana var. 'Elegans', 'Halcyon' or 'Blue Cadet'. You can plant variegated varieties in the shade but you will find that with a lack of light, the colours in the margins will not be as prominent and in some cases may not be very visible.