Vernonia, Aster & Monardella: Three Late Season Blooming Perennials for Colorful, Pollinator-Friendly Gardens
by David Salman
During the excitement of the spring planting season, we often forget about looking for perennials that will bloom much later in the growing season. When gardeners shop for plants in the spring, it’s inevitable that blooming specimens are the first ones chosen. But this front loads the garden with spring color and short-changes the mid-summer to fall flowering season.
One of the key elements to a well-designed, pollinator-friendly garden is to include a diversity of flowering plants that bloom during each of the four parts of the growing season: early spring, late spring, summer, and early fall. You can’t serve just breakfast in spring and forget lunch (summer) and dinner (fall).
For Fall 2019, we are offering three exciting new native perennials that bloom towards the end of the growing season. They are especially good at attracting butterflies as well as native bees and honeybees. Migrating Monarchs need nectar on their way south to their wintering grounds, which makes it all the more important to provide late season natural nectar for them and other butterflies.
Vernonia x ‘Summer Swan Song’ (Hybrid Ironweed)
Vernonia Summer Swan Song (Hybrid Ironweed) Photo courtesy of Homer Trecartin of Twixwood Nursery.
Dr. Jim Ault, plant breeder extraordinaire at the Chicago Botanic Garden, has been working on hybridizing the native Vernonia (Ironweed) to create improved cultivars with better garden performance. He just recently released to growers, his latest beauty, Vernonia x ‘Summer Swan Song’. A cross between V. lettermannii and V. angustifolia, the plant is a stunner. Compact (36” tall x 40” wide at maturity) and sturdy, this hybrid has deep red stems and purple-tinged, olive green leaves and blooms beginning in early to mid-fall with a multitude of large (for Vernonia) deep purple flowers. Grow it in compost-amended garden loam or clay-loam in full sun. Supplemental irrigation is needed during prolonged dry spells. And it’s cold hardy in USDA zones 4-9.
Recommended Vernonia Companion Plants:
This Vernonia is a natural companion for the midsized and taller growing native ornamental grasses like Shenandoah Switch Grass (Panicum virgatum ‘Shenandoah’), Standing Ovation Little Bluestem Grass (Schizachyrium scoparium ‘Standing Ovation’), and Prairie Dropseed Grass (Sporobolus heterolepis).
Herbaceous companions include Blue Fortune Hummingbird Mint (Agastache x ‘Blue Fortune’), Fireworks Goldenrod (Solidago ‘Fireworks’) and Blue Spires Russian Sage (Perovskia atriplicifolia ‘Blue Spires’).
Aster ericoides ‘First Snow’ (Heath Aster)
This is an outstanding heath aster notable for its dense, compact growth habit of tight stems and small leaves that disappear under a cloud of tiny, white daisies in late summer/early fall. Wider than tall, this aster reaches a mature height of 18-24 inches and spreads to a width of 40 inches. Plant it in most any soil including clay in part to full sun. Vigorous and easy-to-grow, its stems are wide spreading and will cascade over the edges of raised beds or follow a slope downward. Cold hardy in USDA zones 4-9.
Recommended Aster Companion Plants:
Ornamental grasses like Blonde Ambition Blue Grama Grass (Bouteloua gracilis ‘Blonde Ambition’), Undaunted® Ruby Muhly Grass (Muhlenbergia reverchonii) and Prairie Dropseed Grass (Sporobolus heterolepis) are excellent neighbors.
Other Aster species and cultivars we offer include 'Professor Kippenberg', ‘Purple Dome’, Raydon’s Favorite’ 'Bluebird', 'Dwarf Alpine' and ‘Lady in Black’.
Monardella villosa ‘Russian River’ (Coyote Mint)
A little known selection of this California native wildflower species, ‘Russian River’ has aromatic dark green foliage, an upright growing habit and large, deep-lavender-pink quarter-sized, puff-ball shaped, late summer flowers. This plant is a delight for nectar seeking bees and butterflies. Grow it in fast-draining sandy or infertile loam soils in full sun (no clay or other heavy soils). Once established, ‘Russian River’ requires little extra water unless a prolonged summer drought occurs. Growing to a height of 15 inches with an eventual width of 18-24 inches, it likes gravel or pine needle mulch, but not moisture-retentive compost or bark. Cold hardy in USDA zones 6-9, it is recommended for fall planting in the warmer winter areas (zones 7-9) only. In zone 6 and cooler, it needs to be spring planted to establish itself with the summer heat before winter.
Recommended Monardella Companion Plants:
Flowering perennials like twice blooming English lavender (Lavandula angustifolia ‘Sharon Roberts’ or ‘Buena Vista’), Licorice Mint Hyssop (Agastache rupestris) and Allium spendens ‘Deep Pink’ (Fall Blooming Korean Onion) are well matched with similar growing conditions and bloom times.