University of Vermont Extension 
Department of Plant and Soil Science

Anytime News Article


SMALL MOUNDED PERENNIALS
 
Dr. Leonard Perry, Extension Professor
University of Vermont
 
There are quite a few small perennials forming low mounds that are suitable for use along walks, rock gardens, and small spaces. All prefer full sun and well-drained soils.

Victor Reiter Common Thrift (Armeria maritima) forms a dense bun or dome less than 6 inches high, and about 4 inches across.  Pink flowers are held above the leaves on stalks in early summer for about 3 weeks.  The bun is made up of narrow leaves less than a quarter inch wide. It is hardy to USDA zone 4a (-30F air temperature) with snow cover, and has proven hardy to a soil temperature briefly of 11F.

The species name indicates that the original species can be found growing along coasts in sandy soil (this plant needs good soil drainage) where it tolerates salt and drought.  In the north, plants prefer full sun to grow best.  There are many other selections of Thrift, such as the cultivar Rubrifolia which is slightly taller, and has rose-red flowers.

Miniature Stonecrop (Sedum requienii) is one of the many low stonecrops you might choose, although it is slower growing than most only reaching about 6 inches high and wide.  Its tiny green leaves are very small, slightly resembling the herb thyme.  Tiny yellow flowers may appear in summer.  It too tolerates drought.  It is hardy to USDA zone 4a with snow cover, or to 11F soil temperatures at least for brief periods.
           
Mountain rockcress (Arabis x sturii) reaches about 6 inches high and wide, the shiny green leaves (under 2 inches long) and small white flowers (spring) making this plant very attractive.  It is hardy to USDA zone 4a with snow cover, and to at least 18F soil temperature for brief periods.  Can't find this species?  The rockcress cultivar Glacier is similar. 
           
Of the many low speedwells you might choose, Mann's Variety (Veronica stelleri) forms a mound about 6 inches high and slightly wider the first growing season.  Dark green leaves have flowers spikes of dark blue rising above them in early summer.  It is hardy to USDA zone 4a with snow cover, and to soil temperatures of 11F for brief periods.  It will tolerate part shade.
           
Alpine or Meadow Moss campion (Silene alpestris) reaches about 6 inches high and wide.  Bright green leaves are covered with double white flowers above them on spikes in early summer. Plants are hardy to USDA zone 4a with snow cover, and for brief periods to ground temperatures of 11F.  They may tolerate part shade.
           
Archer's Gold thyme (Thymus pulegiodes) reaches about 6 inches high and slightly more wide.  As its former species name indicates (citriodorus), it has leaves scented of citrus, more specifically of lemon.  Light lavender flowers appear in late summer above the gold leaves.  It is hardy to at least USDA zone 4a with snow cover, and for brief periods to ground temperatures of at least 18F.  Try this one in raised stone walls where foliage may be brushed, or between patio stones where it may be walked on, to release the aroma.  It grows well in sandy and rocky soils.
            

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