University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article


Dr. Leonard Perry, Extension Professor
University of Vermont

When trying to figure which of the thousands of perennials you should choose for your own garden, you might begin this year with some of the favorites of the perennial professionals. These include an anise hyssop, blue wild indigo, a catnip selection, and a blue stars.  All grow best in full sun, and are great choices for low maintenance.

Each year the Perennial Plant Association, the professional organization for the commercial industry, solicits the top perennials from its members to vote on for perennial plant of the year. These represent those that most growers and designers nationwide feel are most adaptable and worthy of more use. The winner they have already selected for this year is 'Firewitch' dianthus, or also seen by its original German name of 'Feuerhexe' (Dianthus gratianopolitanus).

'Blue Fortune' agastache or anise hyssop is an herb and versatile perennial of the world.  It is a hybrid between a native American species (Agastache foeniculum ) and a Korean one (A. rugosa), and was bred in Holland.  It has the typical anise or licorice-scented leaves of this group, hence the common name.  Leaves and flowers can be used fresh or dried for salads, teas, and garnishes.  Flower stems are easily dried for arrangements.  Leave flowers on the plant to attract bees, hummingbirds, and butterflies.

Agastache flowers are blue-lavender, dense and reminiscent of a bottlebrush.  There are many atop stems reaching two to three feet, and blooming much of the summer.  In fact, the name of this genus is from the Greek for "many flower spikes." This plant prefers dry soil and heat, tolerating drought, but not tolerating wet soils.  It is bothered by few if any pests, and is often left alone by deer and rabbits.  Growing best in full sun, this one will tolerate part shade.  It is most often listed as hardy to USDA zone 5.

Blue wild indigo (Baptisia australis) is one of my favorite perennials, making an "instant shrub" each year in the garden.  The dozens of thick stalks in spring reach three to four feet high, and to six feet across, in early summer.  This mounded "shrub" of blue-green leaves is then covered with deep blue flowers, to be followed in late summer by black seed pods that rattle in the wind.  These are useful for fall and winter effect in the garden, or cut in arrangements.

The deep taproot of this plant means it should be placed properly from the beginning, as it doesn't like transplanting.  But the deep taproot also means this plant withstands drought.  Quite hardy to USDA zone 3, it too does not like wet soils.  It is very low maintenance, with few pests, and makes a nice background for other perennials.

'Walker's Low' catnip (Nepeta x faassenii) provides lovely lavender-blue flower spikes in mid to late summer in the north.  These flowers top the soft, gray-green leaves, which in themselves are fragrant.  This hybrid cultivar (cultivated variety) is lower than its relatives, only growing to 18 inches or so high.  It is also longer blooming, with flowers over a four to six week period, depending on season.  These attract butterflies.

Listed as hardy to USDA zone 5, Walker's Low has proven hardy in zone 4 (much of Vermont).  Coming to us from Great Britain, this low maintenance plant is a great choice for full to part sun gardens.  It resists drought well, resists deer and rabbit feeding, and grows well in average to poor soil, as long as the soil is well-drained.  Use it to edge a perennial bed, massed as a ground cover, or in rock gardens.

Arkansas amsonia was the choice of the professionals, but its close relative blue stars (Amsonia tabernaemontana) is similar, more common, more hardy, and another of my favorite perennials.  While the first is hardy to USDA zone 5, the latter is hardy all the way to zone 3.  This species is native to the eastern states.

Like the wild indigo, blue stars is another low maintenance perennial most gardeners should consider if appropriate, and the space.  It too becomes a shrub by early summer, covered with star-shaped light blue flowers for a stunning display.  Equally stunning is the golden yellow fall color of the narrow and long leaves.

Blue stars forms a mound over three feet high and five feet or more wide, and doesn't require staking if in full sun.  It can tolerate some shade, but may bloom less and require staking there.  It grows best in moist, but well-drained, soils.

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