Mohr's Barbara's-buttons (Marshallia mohrii)

Overview

Marshallia mohrii, commonly known as Mohr’s Barbara’s-buttons, is a charming, rare herbaceous perennial highly valued for its unique summer blooms rising above slender foliage. This species provides subtle elegance to native gardens, offering clusters of pale pink or white disk flowers during the warmer months. Gardeners seek out Marshallia mohrii for its distinct appearance and low maintenance requirements once established in the correct conditions.

It thrives in the unique environmental niches of the Southern Appalachian Mountains, preferring consistently moist, rich soils. While designated as a Threatened Species, home gardeners have an opportunity to cultivate this beauty, supporting its conservation through careful propagation and cultivation outside its precarious native habitats. Growing Mohr’s Barbara’s-buttons successfully requires mimicking its native, seasonally wet environment.

This plant exhibits excellent vertical interest, sending up flower stalks that elevate the blooms well above the basal leaves. For those seeking authentic regional flora, Marshallia mohrii offers low effort for a high seasonal reward, particularly in specialized bog or wet meadow garden settings.

Fast Facts

• Plant Family: Asteraceae
• Plant Type: Herbaceous perennial
• Native Range: Southern Appalachian Mountains
• Hardiness Zones: USDA Zones 7-8
• Size at Maturity:
  • Height: 1.5-2.5 ft
  • Spread: 1-2 ft
• Bloom Time: May to August
• Bloom Description: Pale pink or white
• Sun Exposure: Full sun to part shade
• Water Needs: Medium to wet
• Maintenance Level: Low

How to Grow

The key to establishing healthy Marshallia mohrii is prioritizing soil moisture and drainage simultaneously. Plant during cool seasons, ensuring the location receives full sun to light afternoon shade. The soil must be organically rich and consistently moist but never waterlogged—this is critical, as soils should not be allowed to dry out during the growing season.

Watering needs dictate placement; area Mohr’s Barbara’s-buttons near sources where moisture is naturally abundant, such as pond margins (if drainage is sufficient) or reliably irrigated sections of the garden. Fertilization is generally unnecessary if the native soil is improved with plenty of compost or well-rotted organic matter at planting time.

Maintenance for this species is generally low. Deadheading spent flower heads is optional but can tidy the appearance post-bloom. In late fall or early spring, cut back old, dried foliage close to the ground. Avoid heavy pruning otherwise, as the plant maintains a modest structure, and excessive disturbance can damage its potentially fine root system.

Landscape Uses

Marshallia mohrii is best utilized where its requirement for consistently moist, rich soil can be consistently met, making it an excellent candidate for native rain gardens or watersides. Though it is a Threatened Species and often difficult to source commercially, integrating it into native plant gardens helps preserve its genetic continuity outside of endangered wild populations. Its mid-summer bloom makes it perfect for refreshing borders when early spring flowers have faded.

Consider using Mohr’s Barbara’s-buttons in rock gardens, provided the soil base remains damp beneath stones, or along informal border fronts where its height (up to 2.5 feet) won’t overwhelm shorter neighbors. Pair it with other moisture-loving Appalachian natives, such as specific fern varieties or astilbes, for a cohesive, regionally appropriate display that requires minimal intervention once established.

Standout Features

Flower Qualities

• Showy

Noteworthy Characteristics

Marshallia mohrii, commonly known as Mohr’s barbara buttons, is a perennial herb of the aster family that grows on branching stems to 28” tall. Since 1987, it has been listed as a Threatened Species under the Federal Endangered Species Act of 1973, as amended; it is currently found only in the southern Appalachians in north central Alabama and northwestern Georgia. Erect stems clad with lance-shaped leaves having three conspicuous parallel veins bloom from mid-May to the end of June with five-lobed, pale pink or white disk flowers rising above the foliage. This species has faced habitat loss due to fire suppression and roadside management practices, reinforcing the importance of cultivation in secure garden settings.

Tolerances

Potential Problems

Generally, Marshallia mohrii experiences no serious insect or disease problems when grown in conditions mimicking its native habitat. The primary threat is cultural—planting it in dry, poor soil will lead to rapid decline. Ensure adequate air circulation, especially in humid climates, to prevent any potential fungal issues, although this is less common for this hardy herb.

Frequently Asked Questions

What hardiness zones is Mohr’s Barbara’s-buttons suitable for?

Mohr’s Barbara’s-buttons is suitable for gardeners located in USDA Hardiness Zones 7 through 8.

How large does Marshallia mohrii grow?

It typically reaches a mature height between 1.5 and 2.5 feet tall, with a spread ranging from 1 to 2 feet wide.

What sun exposure does Mohr’s Barbara’s-buttons need?

This plant performs best when situated in a location receiving full sun to partial shade.

When does Marshallia mohrii bloom?

You can expect Marshallia mohrii to bloom from May through August, featuring attractive pale pink or white flowers.

Conclusion

Marshallia mohrii offers gardeners a low-maintenance, unique perennial that adds vertical interest and subtle color during the summer. Cultivating Mohr’s Barbara’s-buttons helps support a federally threatened native species through propagation. Always confirm your local USDA zone compatibility before planting this specialized Appalachian gem.

Companion Planting

When designing a space for Marshallia mohrii, focus on other plants tolerant of medium to wet, rich soils that share the Zone 7-8 hardiness range. Bog mint (Mentha arvensis) or various native sedges (Carex species) work well as stabilizing groundcovers near the base, helping to regulate soil temperatures and moisture levels. Consider pairing it with native irises or cardinal flower (Lobelia cardinalis) which thrive in similar moist meadow conditions and offer contrasting flower colors.

Seasonal Care Calendar

Spring preparation involves cutting back any remaining old growth and incorporating a layer of leaf mold or aged compost around the base to enrich the soil. Summer care centers entirely on consistent moisture; check soil dampness regularly, especially during dry spells, remembering that this plant should never dry out. In autumn, minimal action is required; allow the foliage to naturally senesce unless heavy snow is expected, in which case light mulching might protect very shallow roots in Zone 7.