Trees could play a major role in 15th century religious paintings. In The Stigmatization of St Francis, by Sassetta (1437-44, Room 54), the trees are carefully distinguished from each other and belong to identifiable species. The tree on the right, whose leaves reflect the radiance of Francis's vision of Christ, is a laurel, a tree that symbolised eternal life, and victory over death, because it is an evergreen and one that provided the laurel wreaths for the winners in sporting events. In the centre, next to the tiny chapel, there is a cypress, a tree associated with cemeteries, death and mourning. Its flame-like profile was also loved by Van Gogh, whose painting, A Wheatfield with Cypresses, hangs in room 43.
I love the amazing oak tree in Filippino Lippi's Madonna and Child with SS Jerome and Dominic (c. 1485), room 57. Placed behind the figure of St Jerome, it accentuates the rugged nature of his life in the wilderness, and his steadfastness in his devotion to Christ.
It's difficult to see this detail in the gallery, because it's a large painting - but here you can see (a) that the oak is growing next to a very different tree, which looks like an ash and (b) there is a bird feeding its young at the top of the tree - a parallel to the Madonna suckling her baby. So the artist is not just observing trees, he's interested in the wildlife they support, as well. The leaves of the oak tree are carefully outlined, and the artist has placed leaves lit up by the sunlight against the darker mass of foliage. He's also given his oak tree a gnarled trunk, with stumps where branches have been cut off.
A tree has a starring role in this painting by Gerolamo dei Libri in room 61 - The Virgin and Child with St Anne (1510-18). It's a beautifully painted lemon tree, complete with flowers and fruit. Why does he place his figures against a lemon tree? Possibly because of the associations of lemons with health and cleanliness - it is thought that the painting commemorates a dreadful plague in Verona in 1510-12.
For the last five years, I have been engaged in research for a book on trees in British art, asking questions, such as: how does the interest in trees develop, how do ideas change over the 18th and 19th centuries? I've been looking at drawing manuals, illustrated books on trees, oil paintings, watercolours and prints, landscape gardening, poetry, artists' writings. The artists I'm particularly interested in include the following: Paul Sandby, Thomas Hearne, John Constable, Samuel Palmer, James Ward, John Martin, Edward Lear, Francis Danby, Jacob George Strutt and Henry William Burgess.