Hyssop, or hummingbird mint, provides prolific blooms through the first frost. Look for varieties from the Plant Select program (an initiative between Colorado State University and the Denver Botanic Gardens), which are chosen for their resilience and beauty growing in the mountains and plains. Top picks include orange Sunset hyssop (Agastache rupestris), yellow-orange 'Coronado' hyssop (Agastache aurantiaca 'Coronado'), and lavender-rose Sonoran Sunset hyssop (Agastache cana).
The lush foliage of Bergenia cordifolia 'Autumn Glory' deepens and intensifies with autumn's chill, as does Heuchera sanguinea 'Canyon Duet', a compact coralbell variety with purple-veined dark green foliage that turns reddish. For interesting foliage color that withstands the cold, the Proven Winners Dolce Series doesn't disappoint. Heuchera hybrid 'Key Lime Pie' is chartreuse; 'Blackcurrant' has bold purple leaves with silver accents; and the bronze foliage of 'Creme Brulee' develops brown sugar highlights as the temperature drops.
Ornamental grasses form a dramatic backdrop to fall flowers and foliage, adding texture and movement. Maidengrass (Miscanthus sinensis 'Gracillimus'), feather reedgrass (Calamagrostis 'Karl Foerster'), and switchgrass (Panicum virgatum) form appealing seed heads.
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