Also consider these:
Cornelian cherry dogwood
Cornus mas, Zone 5
‘Lutea Maxima' crown imperial
Fritillaria imperialis ‘Lutea Maxima', Zone 5
Yellow dwarf iris
Iris danfordiae, Zone 4
‘Carlton' daffodil
Narcissus ‘Carlton', Zone 3
Where to get them
KEY: Aurinia saxatilis ‘Goldkugel' (similar to ‘Gold Dust'): 1, Cornus mas: 2, Euphorbia polychroma: 3, Forsythia ‘Northern Gold': 4, Fritillaria imperialis ‘Maxima Lutea': 5, Iris danfordiae: 6, Narcissus ‘Carlton': 7, Primula veris: 8.
B. Dinter Nursery Ltd.: 2.
Botanix Azilda Greenhouses: 3.
Canning Perennials: 1, 3.
Connon Nurseries: 2.
Eagle Lake Nurseries Ltd.: 3, 4.
El Summit Perennials Nursery: 3, 8.
Gardenimport Inc.: 5, 8.
Golden Bough Tree Farm: 2.
Greengate Garden Centres Ltd.: 6, 7.
Hole's Greenhouses & Gardens Ltd.: 3, 6, 8.
Hortico Inc.: 2-4, 8.
McFayden Seed Co. Ltd.: 7.
Pickett's Nurseries: 2, 4.
Richbar Nursery Ltd.: 4.
Richmond Nursery Ltd.: 1, 3, 4, 8.
Via Verde: 5, 7.
Wild Things Plant Farm: 3.
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