Helenium x ‘Double Trouble’ – This Dutch introduction of Sneezeweed features sterile flowers of bright yellow with layered petals surrounding a golden center. These have strong stems and make good cut flowers but may require staking in fertile soils (you can also pinch plants when they are 6-8″ high). Attracts butterflies. Full sun. Grows 30″ high by 18-24″ wide. Zone 4.
Heliopsis helianthoides ‘Loraine Sunshine’ (syn. ‘Helhan’) – A Blooms of Bressingham introduction that was discovered by Loraine Mark of Wisconsin. It features 3″ wide blooms of single yellow daisies from June to October. These are nicely contrasted by unusual variegated leaves of creamy-white with deep green veining. Grows 30-36″ high by 24″ wide. Hardy to zone 3.
Inula ensifolia ‘Compacta’ – A useful slow-spreading rhizomatous perennial for smaller spaces. It bears single golden-yellow daisies with thin strap-like petals and a gold center from June to August. These are nicely contrasted by dark green lance-shaped foliage that forms a dense base. Best in full sun. Divide in early spring or autumn. Grows 6-10″ high by 8-12″ wide. Hardy to zone 4.
Solidago x ‘Golden Baby’ (syn. ‘Goldkind’) – This hybrid Goldenrod is a virtual butterfly magnet and is also grown as a commercial cut flower. The bright yellow blooms are borne as plume-like panicles from July through to September and are sharply contrasted by dark green lance-shaped foliage. A good choice for a mixed border in a cottage garden. Grows 24-28″ high by 18″ wide. Zone 3.
Trollius x cultorum ‘Earliest of All’ – This Globeflower blooms earlier than most and features bright yellow rounded blooms from May to July. These make good cut flowers and are borne over deeply divided mid-green foliage that looks somewhat like buttercup. Prefers rich evenly moist soils and can even be used in boggy conditions. Grows 24-30″ high by 18″ wide. Zone 3.