a plant that makes seeds but not flowers would be Cape Forget-Me-Not

a plant that makes seeds but not flowers would be Cape Forget-Me-NotAnchusa capensis is a hardy biennial with striking deep blue flowers on knee high stems. This versatile plant is perfect for adding vibrant color to flower beds, borders, and containers. Its upright form is ideal for the back of borders and filling gaps between paving stones. Native to much of South Africa's driest regions, it thrives at elevations from sea level all the way to 10,000 feet. Although each plant may only live two or three years,

Anchusa capensis is a hardy biennial with striking deep-blue flowers on knee-high stems. This versatile plant is perfect for adding vibrant color to flower beds, borders, and containers. Its upright form is ideal for the back of borders and filling gaps between paving stones. Native to much of South Africa's driest regions, it thrives at elevations from sea level all the way to 10,000 feet.

Although each plant may only live two or three years, allowing stems to go to seed ensures new plants will grow around it to create a lasting display. This is the perfect mixer for the perennial border and can self-sow moderately to make a considerable statement in time. It needs a good loam to grow well, and grows in amended sandy or clay soils. It needs some consistent irrigation in the heat of summer, in full sun, or hot exposures. Cut back after blooming if you want to prevent unwanted seedlings. Good drainage essential - does not like soggy winter conditions. Remove spent flowers in early July to encourage longer blooming.