Possible Clues:

• They're planted on Arbor Day
• Forest components
• Pear and apple, e.g
• “Poems are made by fools like me” poem
• Holly and Hazel are for the birds!
• Canopy makeup
• What Mark Lanegen climbs?
• Grove contents
• Classic poem that begins 'I think that I shall never see'
• Almonds and pistachios