Answer: Planting beneath trees, especially conifers is a perennial problem for gardeners. Luckily you have good light. It’s usually the tree that wins the competition for water, so before planting try to get a good amount of any well-rotted organic matter mixed into the top 30cm or so of soil to help your shrubs retain water for themselves. In the garden centre you may find ‘well-rotted manure’, composted bark, or bags labelled ‘soil conditioner’. Any of these would be fine.
As for plants, I would look at Nandina domestica for its dense branches of red tinted evergreen leaves, its white flowers and red berries. It will grow to around 1.8m. You may like an evergreen that flowers in winter to early spring, so Viburnum tinus would fill the bill. For another ‘good doer’, try Pittosporum tenuifolium. It can become much larger than you need, but is very amenable to being kept in check with secateurs.
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