University of Vermont Extension
Department of Plant and Soil Science
Summer News
Article
PERENNIAL PLANT
FEATURE—CULVER’S
ROOT
Dr. Leonard Perry, Extension
Professor
University of Vermont
The common name of Culver’s Root
doesn’t do justice to this tall, native perennial that blooms
with generally
lavender spikes in mid to late summer. Although
grown mainly ornamentally now, this plant may be named after a pioneer
physician who advocated use of the root medicinally.
Another member of the figwort family
like the speedwells, Culver’s root differs being taller, with
whorled leaves,
and generally unbranched except at the flowers.
There is generally only one species (Veronicastrum
virginicum) found for sale, along with several cultivated varieties
or
“cultivars”. Flowers are very attractive to bees and other
pollinators such as
butterflies, so they are good for wildlife gardens but not to place
next to a
walk or patio.
Being 4 to 5 feet tall, they are
good for backs of borders or in the centers of island beds. The
statuesque habit makes them good as a
focal point. Or interplant them with upright
ornamental grasses for a prairie or meadow garden. Interplant
some of
the new tickseeds (Coreopsis)
underneath in a mass. The color blends
nicely with Russian sage, or
contrasts with many of the red and pink bee balms.
Flowers appear in mid-summer, lasting
into August in northern gardens, and resemble upright
candelabras. The central flower “spike” is surrounded
by a
whorl of secondary spikes that bloom next, and then flower spikes from
the leaf
axils where leaves join the stems. To
get a more
full cluster of flower spikes, pinch out the central spike as
it’s
forming. These make good cut flowers,
picked ideally when flower spikes are about one-third open.
Over a 5-year period, Richard
Hawke at the Chicago Botanic Garden (USDA zone 5b) conducted a trial of
over 7
selections to determine how they perform in northern gardens. Of
these,
4 rated good and 3 rated poor due to less flower production.
The
top rated included ‘Apollo’, ‘Fascination’,
‘Lavendelturm’ which usually is
seen as Lavender Towers, and ‘Pink Glow’.
All but the last have lavender flowers, the latter being pale pink and
blooming slightly later than the others. The 3 cultivars with fewer
flowers
were ‘Pointed Finger’, ‘Spring Dew’, and
‘Temptation’.
Although ones I have grown in my
Vermont trials have remained upright, without staking, and in good
health,
those in the Chicago trials had lower leaves wither by late
summer. Stems turned brown there, and then the
weakened stems snapped off in the wind.
This may relate to the wet soils at their trial site, and warmer
climate. Cutting plants back to the
ground in late summer produced abundant basal leaves.
Culver’s root prefers full sun
and moist but well-drained soils. Too
much shade and plants will lean toward the light, have fewer flowers,
and may
flop over so need staking. Add
fertilizer in the spring, and again in early summer if plants seem to
lack
vigor and a good green color. Once
established, plants tolerate some drought.
Results of trials on many other perennials can
be found online under the Research section at the Chicago Botanic
Garden (www.chicago-botanic.org/research/plant_evaluation/#notes).
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