Grease 9 x 5 inch (23 x 12 cm) metal loaf pan.
In large bowl, combine 2 cups (500 mL) warm (not hot) water and yeast. Cover and let stand until foamy, about 10 min.
Meanwhile, in another bowl, mix whole-wheat flour, all-purpose flour, plus sunflower, sesame and poppy seeds, and salt. Stir flour mixture with yeast mixture until shaggy dough forms. Tip onto lightly floured surface. Knead about 10 min., or until dough is smooth and elastic, sprinkling with flour as needed to prevent sticking. Shape into an oval loaf. Place in prepared pan. Cover with damp tea towel and let rise until doubled in size, about 1 hr.
Preheat oven to 400°F (200°C). Bake loaf on middle rack 45 to 50 min., or until golden brown. Cool in pan 5 min., then unmold and cool bread on rack.
Substitute equal amounts of pumpkin seeds, golden flaxseeds and hemp seeds for sunflower seeds, sesame seeds and poppy seeds.