{"id":15286,"date":"2026-10-02T12:00:00","date_gmt":"2026-10-02T16:00:00","guid":{"rendered":"https:\/\/whatgrowsthere.com\/grow\/?p=15286"},"modified":"2026-09-30T13:31:18","modified_gmt":"2026-09-30T17:31:18","slug":"update-on-perennial-ironweeds","status":"publish","type":"post","link":"https:\/\/whatgrowsthere.com\/grow\/2026\/10\/02\/update-on-perennial-ironweeds\/","title":{"rendered":"Update On Perennial Ironweeds"},"content":{"rendered":"\n
\"\"<\/a>
Vernonia<\/em> in bloom at University of Tennessee Gardens, Knoxville, TN<\/figcaption><\/figure>\n\n\n\n

U.S. native ironweeds (Vernonia spp.<\/em>) develop a broad visual swath from the mid-Atlantic to the Midwest and from Minnesota south to Texas. Vernonia spp. <\/em>is in the aster or daisy family (Asteraceae). Their abundant purple-hued flowers brighten the autumn landscape from late summer into autumn. Ironweeds serve as an important food source for pollinators. Scores of bees, butterflies, and numerous other insects feverishly work the flowers. <\/p>\n\n\n\n

In general, wild ironweeds grow too tall in most gardens. Recent breeding efforts by Dr. Jim Ault (now retired) at Chicago Botanical Garden has resulted in a number of improved hybrid selections. Late-season bloomers such as sunflowers (Helianthus spp.<\/em>), goldenrods (Solidago spp<\/em>.), and big bluestems (Andropogon gerardii<\/em>) are stellar garden companions.<\/p>\n\n\n\n

Mt. Cuba Center near Wilmington DE conducted a four-year trial that evaluated 45 different Vernonia<\/em> species and cultivars in full sun from 2020-2023. Their focus was on their ornamental and ecological value of ironweeds. Fungal diseases including rust and powdery mildew were common in this trial, although some selections remained virtually free of infection. MT. Cuba Center is located near Wilmington, Delaware and is within USDA hardiness zone 7a.<\/p>\n\n\n\n

The largest ironweed in the MT. Cuba trial was V. gigantea <\/em>ssp. gigantea \u2018Jonesboro Giant\u2019 which topped 12 feet in height; flowers 7-10 days earlier than other varieties; dark burgundy rigid stems stand boldly upright into October; heavy bloomer, massive 12″ wide inflorescences of \u00be-inch-wide purple flowers. <\/p>\n\n\n\n

The soft, needle-shaped leaves of V. lettermannii \u2018Iron Butterfly\u2019<\/strong> is a popular at many garden centers in late summer; grows 2.5 – 3 ft. tall in a mounding habit; purple flowers are highly floriferous; less prone to splaying in the center in heavy rain. Powdery mildew and rust were rarely an issue.<\/p>\n\n\n\n

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‘Southern Cross’ (photo credit: Brent Horvath)<\/figcaption><\/figure>\n\n\n\n

\u2018Southern Cross\u2019 <\/strong>– dark green, willow-like foliage is slightly wider than many ironweeds along with a bronze cast to the terminal leaves and purplish stems; bright purple 1-inch-wide flowers from mid-August to late September; stems sturdy erect with bushy habit (40″ tall x 33″ wide); foliage mildew resistant and rust susceptible. (Brent Horvath introduction at Intrinsic Nursery).<\/p>\n\n\n\n

\u2018Summer\u2019s Surrender\u2019<\/strong> grows 4 ft. tall and 6-6.5 ft. wide with a densely broad habit resembling \u2018Southern Cross\u2019; large clusters of dark purple flowers; foliage resistant to powdery mildew and rust. Bred by Dr. Jim Ault and selected the 2027 Perennial Plant of the Year.<\/p>\n\n\n\n

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Vernonia ‘Summer Surrender’ (2027 PPOY) – Dr. Jim Ault introduction<\/figcaption><\/figure>\n\n\n\n

‘Summer’s Swan Song’<\/strong> (a hybrid cross of V. lettermannii and V. arkansana) has the bushy habit of V.<\/em> lettermannii <\/em>and larger plant size of V. arkansana; olive-green linear foliage. (Jim Ault introduction).<\/p>\n\n\n\n

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September Blooming ironweed<\/figcaption><\/figure>\n\n\n\n

Ironweeds put on an impressive show in native and naturalistic landscapes, meadows, and formal gardens. Powdery mildew and rust can infect foliage in late summer or fall\u2014some species are more susceptible than others. Disease levels can be severe in some years on native populations. The bitter-tasting leaves keep most grazing mammals including deer away. <\/p>\n","protected":false},"excerpt":{"rendered":"

U.S. native ironweeds (Vernonia spp.) develop a broad visual swath from the mid-Atlantic to the Midwest and from Minnesota south to Texas. Vernonia spp. is in the aster or daisy family (Asteraceae). Their abundant purple-hued flowers brighten the autumn landscape from late summer into autumn. Ironweeds serve as an important food source for pollinators. Scores […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[444,657,1218,707,1319,749,1498,645,806,1357,1138,1208,774,1147,853,551,1476,625,1136,1060,1059,729,1220,777,706,646],"tags":[],"_links":{"self":[{"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/posts\/15286"}],"collection":[{"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/comments?post=15286"}],"version-history":[{"count":5,"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/posts\/15286\/revisions"}],"predecessor-version":[{"id":16270,"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/posts\/15286\/revisions\/16270"}],"wp:attachment":[{"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/media?parent=15286"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/categories?post=15286"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/whatgrowsthere.com\/grow\/wp-json\/wp\/v2\/tags?post=15286"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}