Zigzag spiderwort (Tradescantia subaspera)

Overview

The Zigzag spiderwort, Tradescantia subaspera, is a standout herbaceous perennial cherished for its resilience in shaded landscapes. It presents a more robust structure than some of its relatives, easily reaching two feet tall with a distinctive habit known for its zigzag stems. This provides excellent mid-season texture in woodland or naturalized settings where many other perennials struggle with deep shade.

Gardeners appreciate Tradescantia subaspera for its long bloom window, spanning from late spring well into August, offering soft blue or purple coloration. Though individual flowers last only a single day, the terminal clusters ensure a continuous display, making it a reliable component in native plant gardens. The common name, spiderwort, originates from a fascinating physical trait related to its stalk secretions.

As a native plant, the Zigzag spiderwort integrates beautifully into ecological landscapes. It thrives in average to moist conditions, rewarding minimal care with reliable, long-lasting foliage and attractive flowers. Planting Tradescantia subaspera ensures you have structural interest even when other shade-tolerant plants are not in bloom.

Fast Facts

• Plant Family: Commelinaceae
• Plant Type: Herbaceous perennial
• Native Range: United States
• Hardiness Zones: USDA Zones 5-9
• Size at Maturity:
  • Height: 2-2.5 ft
  • Spread: 2-2.5 ft
• Bloom Time: May to August
• Bloom Description: Pale to dark blue, occasionally white
• Sun Exposure: Part shade to full shade
• Water Needs: Medium
• Maintenance Level: Medium

How to Grow

Tradescantia subaspera performs best when planted in spring or fall in locations receiving part shade to full shade. Ensure the planting site has average, well-drained soil, though this spiderwort is notably tolerant of poor soils. It exhibits a preference for moist, slightly acidic conditions, so amend heavy clay soils with organic matter to improve drainage and structure.

Maintain medium moisture levels, particularly during dry spells, as this perennial dislikes drying out completely. Fertilization is rarely necessary, especially if the plant is situated in rich woodland soil. The main cultural task involves managing post-flowering decline; once the summer bloom wanes, cut the foliage back almost to the ground around mid-summer.

Cutting back the foliage prompts a refreshed flush of growth, potentially leading to new blooms later in the season. If conditions are ideal, Zigzag spiderwort can self-seed and gradually spread, which is beneficial for naturalized areas. However, if clumps become overly dense, divide them during the spring or fall dormancy period to maintain vigor.

Landscape Uses

The primary use for Tradescantia subaspera is in creating naturalized drifts, woodland edges, or within shade gardens where its arching foliage provides excellent, continuous ground cover. Its recommended use is to naturalize or incorporate into wild gardens, allowing it to mingle with ferns, Hostas, and woodland phlox. This plant establishes itself well in less-trafficked areas.

When placing Zigzag spiderwort in borders, gardeners must be aware that its foliage tends to sprawl unattractively by mid-summer, necessitating the recommended cutback mentioned in its care guide. For a more formal application, use it toward the back edge where taller foreground plantings can help mask any mid-season untidiness. Its tolerance for poor soil makes it an excellent choice for challenging, dry shade spots beneath mature trees.

Standout Features

Flower Qualities

• Showy

Noteworthy Characteristics

Tradescantia subaspera, commonly called spiderwort, is a clump-forming herbaceous perennial which grows up to 3’ tall. Distinctive zigzag stems and broader leaves distinguish this plant from the very similar Tradescantia virginiana. Violet-blue to purple, three-petaled flowers (.75-1.5” diameter) accented by contrasting yellow stamens open up, a few at a time, each for only one day, from terminal clusters (umbels) containing numerous flower buds.

Tolerances

Potential Problems

The Zigzag spiderwort is generally robust, suffering from no serious insect or disease problems throughout its life cycle. The primary vulnerability occurs when the plant is young. Young shoots are susceptible to snail and slug damage; preventative measures like baiting or hand removal are necessary early in the growing season.

A common management issue gardeners face is the foliage habit late in the season. The leaves of Tradescantia subaspera sprawl in an unattractive manner by mid-summer after the main bloom cycle ends. This is a key indicator that the plant needs pruning; cutting the stems back almost to the ground will tidy the area and encourage a second, smaller flush of attractive leaves.

Frequently Asked Questions

What hardiness zones is Zigzag spiderwort suitable for?

Tradescantia subaspera is hardy in USDA Zones 5 through 9, making it reliably perennial across a wide swath of the Eastern and Mid-Western US.

How large does Tradescantia subaspera grow?

At maturity, the Zigzag spiderwort generally reaches a height between 2 and 2.5 feet and spreads approximately 2 to 2.5 feet wide, forming a substantial clump.

What sun exposure does Zigzag spiderwort need?

This plant thrives best in part shade conditions but is highly adaptable and tolerates full shade very well, making it a versatile choice for darker garden areas.

When does Zigzag spiderwort bloom?

The bloom time for Tradescantia subaspera is typically from May through August, producing flowers described as pale to dark blue, occasionally showing white variations.

Conclusion

The Zigzag spiderwort (Tradescantia subaspera) offers exceptional value to the shade gardener due to its structural zigzag stems and reliable, long-lasting blue flowers. Its tolerance for poor soils and adaptability to deep shade secures its position as an essential native perennial. Before establishing your patch, confirm your location fits within USDA Zones 5-9 and plan for a necessary mid-season haircut to maintain its best appearance.

Companion Planting

When designing a shade garden around Tradescantia subaspera, focus on companions that share its preference for medium moisture and shade. Excellent partners include various ferns, such as Ostrich Fern (Matteuccia struthiopteris), which offer contrasting linear foliage texture. Similarly, woodland ephemerals like Wild Ginger (Asarum canadense) or spring bloomers such as Virginia Bluebells (Mertensia virginica) can fill the space earlier in the season.

The dark green, arching leaves of the spiderwort pair well visually with the lighter, mounding habits of shade groundcovers like Foamflower (Tiarella cordifolia). For height variation without competing heavily for resources, consider taller woodland natives like White Snakeroot (Ageratina altissima), which also blooms later in the summer, complementing the residual flowering of the Tradescantia subaspera.

Propagation Tips

The most straightforward and recommended method for increasing your supply of Zigzag spiderwort is through clump division. This task should ideally be performed in early spring before new growth aggressively emerges or in the fall after the foliage has died back. Dig up the entire clump and gently separate the rhizomes and root divisions, ensuring each new section has healthy roots and several growth points attached.

If propagation via seed is desired, collect the small capsules developing after the flowers fade. Seeds of Tradescantia subaspera often benefit from a period of cold stratification to break dormancy. You can sow them outside in pots covered with grit during the late fall or employ a cold/moist stratification period indoors before spring planting.