Both can be planted in early April and are undeterred by cold snaps or late frosts. Often they're blooming before I remove the cold frames protecting the tender vegetables and flowers. The first full bed I plant each April is a mix of salad greens edged with variegated 'Alaska' nasturtiums. The bright flowers spill over the railroad ties and connect the garden to the path. The flowers, too, are edible and can be used as garnishes or in bouquets.
Nasturtiums quickly germinate and bloom when direct-seeded in cool weather.
Sweet alyssum is a garden angel. When I need something to edge a bed or fill a gap, I sprinkle alyssum seed in early spring, and it sprouts and blooms as quickly as if it were dropped from heaven. The tiny white flowers seem to froth and foam, sweetly scenting the air. Shirley poppies, too, are early bloomers that come and go without crowding out others, taking their leave in early summer. They are the most impractical flower for cutting, lasting hardly a weekend in water, but I grow them because their beautiful gossamer petals are heart-stoppers.