Late Summer And Fall Plants For Color

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Presented by Dr. Sue Hamilton, University of Tennessee

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Late Summer And Fall Plants For Color

  1. 1. What to do When Summer Sizzlers Fizzle!! Dr. Sue Hamilton University of Tenneessee sueham@utk.edu Late summer and fall isn’t too late for garden fireworks, especially if you include the right late- season plants. Just when you think the gardening season is over and there isn’t much to enjoy, the following annuals and perennials can throw a color party as one last hurrah before winter. Sunflowers, Marigolds, and Zinnias: Since the average killing frost in Tennessee is around November 1st, a late planting of these summer annuals can enliven a fading garden. Planting around August 1st will ensure brilliant flower colors until a killing frost. What is especially easy about these annuals is that since their seed is so large, you can sow their seed directly into the ground thus eliminating any transplanting. Sow seed about 1" deep and 12" apart being sure to cover with a fine soil. Once the seed has germinated, be sure to use a light mulch around the plants to reduce the incidence of weeds and to hold in moisture. Annual Vines: Several annual vines, if planted in the early summer, can provide incredible fall color in the garden. One of my favorites is Lablab purpurea (Hyacinth Bean). This fast growing cousin of the sweet pea produces loads of flowers and fruit from mid-summer until a killing frost. Its profuse lilac flowers and purple bean pods are incredibly showy and edible. This annual vine will climb 10 to 12 feet on most any garden structure. It prefers full sun and will grow in average garden soil. An easy vine for the beginning gardener. Hyacinth bean establishes best in the garden when directly sown once night temperatures are above 50 degrees. Another colorful climber is Mina lobata (Spanish Flag or Firecracker Vine). This annual vine produces the most colorful flower show I have ever seen on any vine! The autumn color-correct flowers bloom from late summer until a killing frost providing a showstopper performance. Each spike has up to 12, one inch tubular flowers that begin as a rusty red color changing to orange then to yellow and finally maturing to white. All colors appear on the plant at the same time making a dramatic show. The 5-inch leaves are dark green and shaped similar to that of a sweet potato plant. Firecracker vine can grow 10 to 12 feet rambling over a trellis or fence. It prefers full sun and a moist, well-drained soil. One other vine I would recommend is Cypress Vine (Ipomoea quamoclit). This vigorous, fast-growing vine smothers itself with scarlet, trumpet-shaped flowers from midsummer until frost. The fine-textured foliage can quickly form a screen when planted on a fence or any structure to which it can cling. Cypress vine will climb 10 to 20 feet and will cover itself in one inch flowers. It prefers full sun and average garden soil. The scarlet flowers attract hummingbirds and butterflies. The cypress vine is easily mistaken for cardinal vine (Ipomoea x multifida), which also produces similar red, trumpet shaped flowers but has larger, palm-shaped leaves and fewer flowers. For flower show, cypress vine is preferred. It readily self-seeds. Hardy Annuals: Since Tennessee has moderate temperatures in the winter months, there are several annuals which we consider “cold-hardy” since they are able to survive and thrive through the winter season. Pansies, violas, snapdragons, and Dianthus chinensis are terrific cold-hardy annuals which flower from the time they are planted until the following spring. It is best to purchase such plants from a nursery or garden center since they are not easily grown from seed in the garden. Planting in September or early October is ideal so plants can get established before cold weather really sets in. Mass plantings generally make the most impressive show. Since these plants are not
  2. 2. big in size, plant 6" - 8" apart. If you want to have a truly impressive spring garden, consider interplanting tulip or daffodil bulbs with these annuals. Planting the bulbs between your hardy annuals will bring a surprise burst of color in the spring. And when the fading bulb’s foliage begins to wither, the hardy annuals are so colorful that one barely notices the yellowing foliage. Combining so many plants into one garden certainly is not the cheapest garden you’ll ever plant but well worth the price of spring enjoyment. This practice is common among botanical gardens who generally have admission fees for such displays. Pine needles are the ideal mulch for overwintering these colorful annuals since they are not heavy and provide great insulation. Solidago (Goldenrod) A great bloomer in September and October, Goldenrod enlivens the garden with bright gold flowers. Though a great native plant, outstanding hybrids exists with superior characteristics. ‘Fireworks’, introduced by Kim Hawks of Niche Gardens, grows 3' - 4' tall and has strong sturdy stems preventing lodging. It produces a profusion of flowers like no other cultivar. ‘Baby Gold’ and ‘Crown of Rays’ are both compact varieties growing to 24" and flowering mid- summer thru fall. Goldenrod has been unfairly accused of causing hay fever which is really caused by ragweed, an entirely different plant. Aster If you’d like to include colors in your autumn garden other than those which are fall-correct, consider using perennial asters. In contrast, wispy asters bloom in blues and purples that complement the yellows and coppers of goldenrods, perennial sunflowers, and sedums. For height, consider using A. tataricus (Tatarian Daisy) which grows to 6' and requires no staking. Flowers are a beautiful lavender color. The Frikart’s Aster (A. x frikartii) grows 2' - 3' and has a loose and tumbling growth habit with lavender blooms. The New York Aster (A. novi-belgii) and the New England Aster (A. novae-angliae) are both great selections for the variety of cultivars, heights, and colors available. All are great for attracting butterflies. Sedum (Showy Stonecrop) One of the best perennials available to gardeners for year round garden merit, particularly for its blue-gray foliage color. However, autumn is when sedum really grabs your attention. ‘Autumn Joy’ and ‘Matrona’ are two choice hybrids for their large and showy bronze- colored blooms. They each grow to 24". ‘Ruby Glow’ and ‘Vera Jameson’ are creeping forms growing to 12" with both producing dark ruby-colored blooms. Sedum thrives in sun or light shade and well-drained soil. Helianthus (Perennial Sunflower) These plants are not for the timid gardener. Most species bloom bright gold in late summer through fall and need considerable room since most grow anywhere from 5' - 9' tall. H. simulans (Tall Narrow-leaved Sunflower) is one of latest bloomers persisting into November well after hard frosts. Other great species to collect include H. tomentosus (Hairy Sunflower), H. atrorubens (Yellow Sunflower) , H. angustifolius (Narrow-leaved Sunflower) and H. giganteus (Giant Sunflower). All thrive in sun and a wide range of soil types. Salvia (Perennial Salvia) Those who know Salvia only as an annual bedding plant are surprised to learn that this is a vast genus, consisting of over 700 species. There are several outstanding perennial species which flower well into the fall season. One of my favorites is S. guaranitica (Blue Anise Sage) which is loaded with blue flowers from early summer to a killing frost. It grows 3'-4' tall and numerous cultivars are available. S. greggii (Texas Sage) is another all-season bloomer providing great color through fall. Flower colors available include red, coral, white, pink, and pale yellow. Some great fall-season salvias are only marginally hardy and easily die-out during the winter. Their spectacular fall show makes them worth replanting each year if needed. S. elegans (Pineapple Sage) is
  3. 3. wonderfully fragrant and blooms brilliant red from September until a killing frost. S. leucantha (Mexican Bush Sage) has impressive purple and white flowers with spikes 1' - 2' long. S. van houttei (Wine Sage) has beautiful cranberry-colored blooms flowering from mid-summer until a killing frost. S. ‘Indigo Spires’ and S. ‘Purple Majesty’ are outstanding hybrids for their long flower spikes as well. All of these marginals grow 3'-4' tall and make excellent cutflowers. Mulch these salvias with pineneedles to improve their over-wintering. Salvias prefer sun and well-drained soils. Chrysanthemum (Garden mum) The good old garden mum is really a hybrid of several species native to China and Japan that breeders have been working with for hundreds of years. Garden mums produce green foliage all summer and then with decreasing day length and cooling night temperatures, they bursts forth with exuberant bloom. Just about every color but true blue is available. Besides a variety of colors, you’ll find mums with interesting flower forms with names like spider, spoon, decorative, button, and daisy. The modern garden mums are bred to have neat, compact habits that are either mounding or slightly upright and vase-shaped with blooms lasting up to 3 weeks. Most varieties will top out at 18" - 24". Not all garden mums are reliably hardy. For those that do return year after year, consider cutting them back to 3" above the ground around July 15th to ensure compact plants which won’t lodge once loaded with blooms in the fall. Garden mums are heavy feeders so provide good fertilization throughout the season. Patrinia (Patrinia) P. scabious (Scabious Patrinia) is gaining in popularity as gardeners discover its fall-season merit. The bright gold blooms, which have a fine texture, shimmer in the autumn garden. Growing to 4' tall with strong, erect stems makes it a striking plant. Useful as a cutflower and for attracting butterflies. P. villosa (White Patrinia) is another outstanding species which was introduced by Dan Hinkley of Herronswood Nursery. This 2'-3' tall plant is not erect but sprawling and loaded with white blooms. Both species thrive in sun and well-drained soils. Ornamental Grasses No garden is complete without ornamental grasses. This is never so true than in the autumn garden. Numerous grasses peak during the fall adding spectacular form and texture to the garden. One of my favorites is a native grass, Sorghastrum nutans (Indian Grass). The tall narrow clumps of this graceful grass grow to 4' tall making it a good vertical accent in the mixed border. The slender leaves are light green or blue in summer, bronze or burnt orange in fall, and rich gold in winter. The amber flower heads in autumn can be used in fresh or dried arrangements. Pennisetum alopecuroides (Fountain Grass) is a small, compact grass for the autumn garden growing only 2' -3' tall. It flowers freely from mid-summer to mid-fall with stems of fluffy fox-tail like spikes spilling outward like a fountain. The foliage turns bronze and orange in the fall. Panicum virgatum (Switch Grass) is a terrific grass for its soft texture and graceful form. Two superior cultivars for autumn color are ‘Haense Herms’ (Red Switch Grass) and ‘Heavy Metal’. Both grow 3' -4' tall and turn red and orange in the fall. One last suggested grass for fall color is Imperata cylindrica (Japanese Blood Grass). Leaves become flushed with garnet red as summer progresses, darkening into burgundy toward fall. Growing only 12" - 18" tall, use it for an accent plant, especially in a west- facing location where it can be backlit by the setting sun. Amsonia (Blue Star Flower) A beautiful spring flowering perennial with vibrant light blue blooms that has a spectacular foliage show in the fall. A. hubrectii (Arkansas Amsonia) is the best species for fall foliage. The feathery foliage is soft and green all season but makes a sensational show in the fall. Allan Armitage claims that this species is “second to none among herbaceous plants” with its golden-yellow fall foliage. A. tabernaemontana has coarser foliage and brighter blue flowers than the other species but its fall foliage is just as colorful. Both species thrive in sun and well-drained soil
  4. 4. and are most showy if planted in mass. Anemone (Windflower) Anemone is a huge genus consisting of spring, summer and fall flowering species. None is better for the fall garden than A. x hybrida (Japanese Anemone). The tall stature, growing 4' - 5' tall, and profuse bloom habit make it a striking plant in the autumn garden. Numerous cultivars exist available in a variety of bloom colors including white, various shades of pink, and lavender. Cultivars of single, semi-double, or double blooms are also available. A well- drained site in either sun or partial shade is ideal.

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