If you missed the opportunity to start flower seeds earlier in the year, you can still sow these varieties for late season bloom.
Calendula takes just 6-8 weeks to grow from seed and the flowers are fairly cold-hardy. Thrives on minimal care. Grow in part-sun to full sun environments, and don't mind poor soil. Deadhead spent flowers.
Sweet Alyssum are fast growing (in as little as four weeks you could have blooms)! Plant in a sheltered spot that gets sun but not high summer heat (instead, a little afternoon shade is welcomed by these pretty flowers). Require regular watering.
Nasturtium is an old-fashioned fave because it's so easy to grow (and all parts of the plant are fully edible). Take it from seed to full bloom in just 4 - 6 weeks. Plants are often trailing and climbing.
Black-Eyed Susan (also called rudbekia) has a bright yellow daily-like bloom with a dark center. Takes 2-3 months to grow. Likes full sun to light shade and is heat tolerant, drought resistant, and self-seeding. Deadhead to keep blooms coming and prevent plant from going to seed.
Marigolds are those wonderful garden flowers that add a cheerfulness to any area of the garden. They germinate quickly and bloom in about 8 weeks. Sow seeds 1 inch apart and water thoroughly after planting (same goes for all the flowers listed here).
Photos show flowers from top left clockwise in the order written.