University of Vermont Extension 
Department of Plant and Soil Science

Summer News Article

Dr. Leonard Perry, Extension Professor
University of Vermont
Meadow rues are a group of easy-care perennials, growing in various habitats from sun to shade.  With a diversity of flowers, leaves, and growth habits, they offer lots of options in many gardens.

Although there are at least 130 species of this perennial known in the world, only about a dozen and a half and their cultivars are more commonly found for sale.  These were evaluated by Richard Hawke in trials at the Chicago Botanic Garden recently, with a wealth of comparative information and the following suggestions for the best selections.  Even though this site is in USDA zone 5b (-10 to -15 degrees F in winter), most species that were hardy there also are hardy in much colder zones such as in northern Vermont.  Meadow rues are native to northern temperate zones of the world, with some native to Siberia and the Far East.

The meadow rue genus (Thalictrum) is in the buttercup family, as are its relatives the columbine, delphinium, and hellebore.  Some form clumps, others spread by underground stems called rhizomes.  They range from six inches to over 10 feet tall.  The fine-textured leaves are feather-like, or fern-like divided into groups of three.  Perhaps the most interesting part of their botany is their showy flowers, which lack petals.  Some species have flower parts called sepals that resemble petals, others just have a dense group of the stamens—the male flower parts—that provide the show.  Depending on the species, flowers may be in bloom from late spring to early fall.

Meadow rues prefer moist, organic and well-drained soils.  The columbine meadow rue (T. aquilegifolium), named from the fact the leaves resemble columbine (Aquilegia), needs consistent moisture especially if in full sun.  Most meadow rues in the Chicago trials, in a clay loam soil, grew best in full sun even though they are often recommended for part shade sites.

Meadow rues don’t require much fertility, that from organic fertilizer or compost often sufficient.  They don’t require much care, and are generally pest free.  Some species may get powdery mildew and leaf miners.  If a plant becomes ragged after bloom, it can often be pruned to the ground to encourage new growth.

The first to bloom of the best selections in the Chicago trials was the columbine meadow rue already mentioned, which bloomed mid-May to mid-June.   The most common cultivar (cultivated variety) of this species, and the one that was more robust with more flowers, was ‘Purpureum’.  It has blue-green leaves, grows about four feet tall, and has an inflorescence (group of flowers) up to six inches across.  Individual flowers are up to an inch across, lavender, and resemble pompoms.  They have no sepals, only stamens.  Also as noted already, this species needs more moisture than most others, and may get some powdery mildew.

Many meadow rues bloom in mid-summer.  The yellow meadow rue (T. flavum ssp.glaucum) and the cultivar ‘Illuminator’ both rated more highly than the cultivar ‘True Blue’.  The former has blue green leaves, reaches about six feet high, and has yellow flowers of only stamens in July.  This plant can spread by rhizomatous stems, forming not a thicket but rather groups of distinct plants.  ‘Illuminator’ is similar only shorter (four feet), and leaves emerge yellow in spring, later turning blue-green. 
Another tall, mid-summer meadow rue with yellow flowers (T. lucidum) is different from the others, having linear leaflets emerging purple, then turning green.  The clusters of pale yellow flowers can reach nine inches across.  The lesser meadow rue (T. minus ‘Adiantifolium’) has leaves resembling the maidenhair fern (Adiantum).  Reaching about five feet high, the yellow flowers are small and in more open inflorescences, so impart a fine texture.  Its leaves emerge bronze, then turn blue-green. 

The tall meadow rue (T. pubescens) is a different one for mid-summer bloom, having creamy white flowers composed only of stamens, and reaching up to 10 feet tall.  On the other extreme is the Kyushu meadow rue (T. kiusianum), only reaching about six inches tall.  It too blooms in mid-summer, only with pink flowers composed of stamens.  It performed better in trials than another dwarf species (T. ichangense).

Blooming from mid-summer to early fall is the lavender mist meadow rue (T. rochebruneanum).  Unlike most other meadow rues, this one has prominent lavender sepals in the flowers surrounding the yellow stamens.  This species and cultivars reach about six feet high, and with an open habit have a “see through” quality.  In the Chicago trials there were no differences among the species and cultivars ‘Lavender Mist’ or ‘Purple Mist’.  The cultivars often had minor powdery mildew, not seen on the species.   

Blooming from mid to late summer is the cultivar ‘Elin’, supposedly a hybrid of the lavender mist and the yellow meadow rues.  Although the flowering was similar to the lavender mist, it bloomed a couple weeks earlier.  It was more vigorous than either parent, reaching eight feet high.  It did not drop leaves and thin out later in the season, as lavender mist tends to.  It can get powdery mildew, and slight leaf miner damage.
Whether for part shade or full sun, consider the taller meadow rues for backs of borders or centers of island beds.  The medium height species might be placed in small groups throughout beds.  Of course the dwarf species can be massed along the fronts of beds, or grown in raised gardens and rock gardens where they can be seen better.

The fine-textured meadow rues can be combined with the coarse-textured rodgersias (Rodgersia) and ligularias (Ligularia) for dramatic contrast.  In full sun, try them with daylilies (Hemerocallis), garden phlox (Phlox paniculata), and ornamental grasses.  In part shade, try them with turtleheads (Chelone) and ferns. 

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