HARDINESS: Zones 4 to 8
PREFERRED SOIL pH: Near neutral
PREFERRED SOIL TYPE: Average, moist
PREFERRED LIGHT: Sun to partial shade
ATTRIBUTES: Upright plants with blue, pink, or white flowers; for beds, meadow gardens
SEASON OF INTEREST: Late spring through summer
FAVORITES: 'Purple Profusion', 'Snow-cap', 'Zwanenburg Blue'
QUIRKS: Flowers last only a day, but new ones open dairy
GOOD NEIGHBORS: Columbine, daylily, ferns, foxglove, ornamental grasses, hosta, iris
WHERE IT GROWS BEST: In partial shade and moist, average soil
POTENTIAL PROBLEMS: In favorable sites and climates it can become moderately invasive
RENEWING PLANTS: Lives many years; divide crowded clumps in early spring every 4-5 years
CRITTER RESISTANCE: Good
SOURCE: Division, self-seeds
DIMENSIONS: 10-24 in (25.4-61 cm) tall and 10-18 in (25.4-45.7 cm) wide
Spiderwort in the Landscape
This pretty North American native plant grows with vigor and ease in most parts of the country. Adaptable to variable conditions, spiderwort is at its best in warm-summer sites and moist soil. A strongly upright plant that bears lilac blue 3-petaled flowers over a 2-month period, spiderwort is a natural choice for sunny flower gardens in cool-summer climates or shady areas in warm regions. The triangular flowers appear in small clusters at the stem tips and close at night, with new buds opening every day.
Spiderwort is ideal for filling low spots in gardens or wild meadows. In a long flower border that is partly in sun and partly in shade, use it as a "repeat" plant to tie the border together. Spiderwort thrives in deeply
dug, well-drained beds, but it can also tolerate wet-soil conditions that give other flowering plants trouble with root rot.
Glistening, intensely saturated flower color in late spring through summer is spiderwort's main charm. Most plants sold for the garden are hybrids between several species. The cultivar 'Purple Profusion' grows 18 in (45.7 cm) tall with a long season of bluish purple flowers set off by yellow stamens. 'Zwanenburg Blue' offers flowers of a rare royal blue and foliage veined in purple, while 'Pauline' has large pink flowers. A white form, 'Snowcap', provides sparkling contrast when paired with blue cultivars.
There are also compact spiderworts, at 10 in (25.4 cm) tall, which are ideal for smaller gardens. These include 'Bilberry Ice', which has two-toned flowers with lavender streaks, and rose-flowered 'Red Cloud'.
Set plants out in early spring, 12 in (30.5 cm) apart. Plant them at the same depth they occupied in their nursery pots and water as needed to keep soil moist for a few weeks until they show signs of growth. Ideally, soil should be moist and loamy, but spiderwort can also adapt to drier conditions after its first year in the garden. Fertilize plants each spring with a deep drench of liquid all-purpose plant food, mixed according to label directions.
In summer, after the plants have finished blooming and the straplike foliage becomes yellowed, cut plants back to 2 in (5.1 cm) from the ground. Abundant rainfall, or irrigation, will often coax a second flush of foliage and flowers. However, more often the plants will simply go dormant until the following spring.
Increasing the Bounty
Every 4-5 years in early spring, dig and divide clumps. Look for points of narrow foliage poking through the soil's surface at about the time early daffodils bloom. Use a spade or a sharp knife to cut the large mass into smaller dumps, each of which should have 3 or more crowns. Transplant individual clumps to their new locations and water immediately. In mild-winter climates, you can also dig and divide large clumps in the fall. When grown in spots they like, spiderworts self-sow easily. You can dig and move seedlings in spring in colder regions, and in spring or fall in mild climates. These stalwart natives are rarely if ever visited by pests or diseases.