The autumn perennial garden should be both a plenitude of special delights and a sphere of robust activity. The challenge is to find plants that delay or prolong their bloom until this equinoctial period.
For the fearless full-sun gardener, Helianthus maximilianni, Maximilian sunflower, is a 6′ yellow-gold explosion of 3″ daisies from August to frost. Don’t coddle this tough native giant with too much water or fertilizer, as you will compromise its upright nature.
A wonderful grass companion that brings a touch of sophistication to the sunflower’s exuberance is Molinia caerulea ssp. arundinacea, also known as Skyracer, a tall moor grass. Known for its swish and sway in the slightest breeze, its autumn-tawny slender spears shoot skyward (up to 8′) from a graceful grassy mound. Group this hardy grass in front of the sunflowers or as an architectural specimen where a dramatic exclamatory statement is needed.
The fall-flowering stalwarts are the asters and chrysanthemums. The Aster novae-angliae cultivars are unmatched for sheer flower power. Harrington’s Pink, Alma Potschke, Purple Dome, and Hella Lacy are sure performers both in the border (with staking) and vase; but for something very late and remarkable, try Aster tataricus, Tartarian aster, which can reach 6′ with strong stems of yellow-centered lavender-blue daisies.
The Korean hybrid chrysanthemums are late, choice, and naturally compact. “Ryan’s Daisy” and “Hillside Sheffield” are worth trying for their pastel shades and abundant flowers. Other chrysanthemum cultivars such as Clara Curtis (rose pink) and “Mary Stoker” (pale yellow with pink blush) are floriferous, which come up a little earlier and taller, and are quite endearing.
Two fabulously hued, small-statured native grasses that work well with them are Sporobolus heterolepis, prairie dropseed, and Schizachyrium scoparium, little bluestem. Both are medium in height (3-4′), clumping in form, late flowering, and ablaze in coppery or flaming orange-gold-red colors respectively.
Finally, for the woodland edge, the toad lilies, Tricyrtis hirta and T. formosana, are bejeweled treasures reaching 2-3′ with a relaxed clumping habit. Naturally, they work well with drifts of the Hakone grasses, Hakonechloa macra cultivars. With the right light and a few well placed stones, the dark green, wiry bladed sheep’s fescue, Festuca amethystina, is also a delightful companion.
Fall is the best time for planting herbaceous perennials. Lead off with bareroot peonies, move to other fleshy-rooted genera like Papaver (oriental poppies), Platycodon (balloonflower), Dicentra (bleeding heart), and Baptisia (false indigo), and continue with nearly any well-rooted plant material at least into mid-October.
With the focus on flowers, new plants, and fall blooms, remember the main points: well-prepared planting beds with keen attention to soil drainage, proper depth placement of the plant crown or root section, and winter mulching at the proper time. With the cooling soil temperatures, shorter days, and normally abundant autumnal rainfall, a good watering in at planting time will usually be sufficient until new growth occurs in spring.