University of Vermont
Department of Plant and Soil Science
PERENNIAL PLANT FEATURE: SPIDERWORTS
Dr. Leonard Perry, Horticulture Professor
University of Vermont
Spiderworts are a more attractive perennial than their name suggests.
They flower in early summer, in a range of colors depending on cultivar
(cultivated variety). With proper choices, and a little care, you can
have plants free of disease and that don’t self seed.
The name, spiderwort, likely refers to the fact that sap released from the
stems dries into web-like threads. Another name, dayflower, refers to
the fact that individual flowers only last for a day. Yet, with many
flowers in clusters on the ends of stems to 24 inches tall, blooming lasts
for two or three weeks in late spring (South) or early summer (North).
Rebloom may occur later in summer or early fall.
Depending on cultivar (cultivated variety), blooms can be had in a range of
colors including blues, violets, purple, pinks, and white. Observe
them closely, and you’ll see why some call them “trinity flower.” Each
bloom has three petals, three sepals (parts resembling petals), and six
stamens. Observe the stamens even closer, and their fuzzy stalks
(“filaments”) with bright yellow anthers (the pollen carriers) on the tips
appear like a drawing from Dr. Seuss.
The strap-shaped leaves are mainly green, but on some cultivars may be
blue-green, chartreuse, or bright yellow. Often the bright yellow ones
revert to mostly green over a few years. These leaves are quite dense
early in the season, but tend to die back or become unsightly after bloom
and when plants go dormant in summer heat. They’ll last better in cool
seasons, cool climates, and if kept watered. Otherwise, if leaves
become unsightly and deteriorate, cut them back to the ground, and new ones
will arise with cooler temperatures later in the season.
Cutting stems back also will remove the untidy flowers, which tend to hang
on a while after bloom, and prevent seeds forming. If seeds are
released, the subsequent unwanted seedlings can fill a bed—another trait
that may turn some gardeners away from this plant. If you only have
one plant, you don’t need to worry about seeds, as plants are “self
sterile”. This means that at least two plants are needed to
cross pollinate and form seeds.
Height and width at bloom varies with the cultivar, but may range from one
to two feet high, and two to three feet wide. Spiderworts prefer full
sun for best bloom and growth (eight or more hours of direct sun daily), but
will tolerate part shade (four to eight hours of direct sun). They’re
hardy, surviving in USDA zone 4 (-20 to -30 degrees F), such as in most of
northern New England.
Spiderworts are good choices for feeding bees and butterflies. Their
overall appearance makes them good choices aesthetically for cottage
gardens, woodland edges, watersides, and meadow plantings. While they
prefer a slightly moist soil, it should be well-drained and not get too
dry. Consider combining them in sunny gardens with perennial
geraniums, bluestars, or ornamental grasses. In part shade, consider
them with hostas, astilbe, lungworts, and ferns. Combining them with
perennials works well to hide their leaves if they become unsightly, need to
be cut back, or plants go dormant.
Although there are about 70 species of spiderworts, most cultivars you’ll
find for sale are crosses among three—Virginia (virginiana),
bluejacket (ohiensis), and zigzag spiderwort (subaspera).
These crosses are correctly lumped into the Andersoniana group, although you
may find them listed incorrectly under a hybrid species (xandersoniana).
All are native to the eastern United States, even though they’re in the
mainly tropical dayflower family along with such houseplants as
Moses-in-a-boat and wandering Jew.
These main spiderwort species were among the first plants introduced to
Europe from the New World in the early 1600s. The Virginia spiderwort
was used medicinally by Native Americans to treat many ailments. An
interesting and odd fact about some species is that the fuzzy hairs on the
flower filaments change from blue to pink upon exposure to low levels of
As part of the extensive perennial evaluation program of Richard Hawke at
the Chicago Botanic Garden (www.chicagobotanic.org/research),
31 different spiderworts were grown and rated yearly for growth
characteristics and resistance to leaf-spotting diseases. Fourteen of
these received top 4-star ratings and are listed in the website
While a good flower display on spiderworts consists of open flowers on at
least 50 percent of flower clusters (inflorescences) at peak bloom, the
cultivar ‘Red Cloud’ (rosy red flowers) was the best in the Chicago trials
with 70 percent open flowers. It produced flowers that lasted through
the day too, unlike most cultivars that finish blooming around mid-day.
Others with consistently good blooming in the trials, as well as low disease
ratings, were ‘Blue Stone’ (lavender blue flowers, yellow green leaves),
‘Concord Grape’ (purple flowers, blue-green leaves,early season bloom),
‘Perinne’s Pink’ (pink flowers, blue-green leaves), and ‘Zwanenburg Blue’
(purplish blue flowers, green leaves).
Leaf diseases don’t occur in all garden settings, or in all years. To
avoid plants getting these, avoid overhead watering, and choose least
susceptible cultivars. If leaves become diseased, cut them back if
severely infected or as they die back after bloom and discard (don’t
compost) leaves in the trash.
Return to Perry's Perennial