'Orchid Beauty' Butterflybush Orchid Rock Rose
'Orchid' Saucer Magnolia: soulangianahybrid Orchid Tree
Orchid Tree, Hong Kong Orchid Tree, Purple
Orchid Tree, Variegated (spp.) Orchid Tree, Variegated 'Candida'
Orchid Tree, White Orchid Tree: grandidieri
Orchid Tree: ramosissima Orchid Tree: spp.
Orchid, Philippine Oregon Cedar (spp.)
Oregon Cedar 'Aurea Densa' Oregon Cedar 'Columnaris'
Oregon Cedar 'Erecta' Oregon Cedar 'Fletcheri'
Oregon Cedar 'Globosa Nana' Oregon Cedar Golden
Oregon Cedar Golden Oregon Cedar 'Green Pillar'
Oregon Cedar 'Intertexta' Oregon Cedar 'Lane'
Oregon Cedar 'Lane's Aurea' Oregon Cedar 'Minima Aurea'
Oregon Cedar 'Pembury Blue' Oregon Cedar 'Pottenii'
Oregon Cedar 'Triomf van Boskoop' Oregon Cedar 'Wisselii'
Oregon Cedar 'Yvonne' Oregon Grape 'Skylark'
Oregon Grape (spp.) Oregon Grape 'Apollo'
Oregon Grape 'Compactum' Oregon Holly Grape (spp.)
Oregon Holly Grape 'Apollo' Oregon Holly Grape 'Compactum'
Oregon Holly (spp.) Oregon Holly 'Apollo'
Oregon Holly 'Compactum' 'Oregon Jade' Mugo Pine
Oregon Maple Oregon White Oak
Organ Pipe Cactus 'Orido Nishiki' Japanese Maple
'Oridono nishiki' Japanese Maple Oriental Alder
Oriental Arborvitae (spp.) Oriental Bittersweet
Oriental Cherry (spp.) Oriental Cherry 'Kiku-Shidari'
Oriental Cherry 'Kwanzan' Oriental Cherry 'Ojochin'
Oriental Cherry 'Royal Burgundy' Oriental Cherry 'Shiro-Fugen'
Oriental Cherry 'Tia Haku' Oriental Oak
Oriental Paper Bush (spp.) Oriental Paper Bush 'John Bryant'
Oriental Paper Bush 'Winter Gold' Oriental Pear
Oriental Photinia Oriental Planetree (spp.)
Oriental Planetree 'Insularis' Oriental Spice Bush
Oriental Spruce (spp.) Oriental Spruce Golden
Oriental Spruce 'Nigra Compacta' Oriental Spruce 'Rara Flora Fluke'
Oriental Spruce 'Skagit' Oriental Spruce 'Skylands'
Oriental Sweetgum Oriental Sycamore (spp.)
Oriental Sycamore 'Insularis' Ornamental Peach (spp.)
Ornamental Peach 'Corinthian Mauve' Ornamental Peach 'Corinthian Pink'
Ornamental Peach 'Corinthian Rose' Ornamental Peach 'Corinthian White'
Ornamental Peach 'Icicle' Ornamental Peach 'NCSU Dwarf Double Red'
Osage Orange (spp.) Osage Orange 'Double O'
'Oshi Rini' Japanese Maple 'Oshio beni' Japanese Maple
Osmanthus, Roundleaf Holly Osmoxylon
'Oso Easy® Cherry Pie' Rose 'Oso Easy® Honey Bun' Rose
'Oso Easy® Lemon Zest' Rose 'Oso Easy® Mango Salsa' Rose
'Oso Easy® Strawberry Crush' Rose 'Oso Easy™ Paprika' Rose
'Oso Easy™ Peachy Cream' Rose 'Oso Easy™ Fragrant Spreader' Rose
'Oso Happy® Candy Oh!' Rose 'Oso Happy® Petit Pink' Rose
'Oso Happy® Smoothie' Rose 'Ospring' Chinese Holly