North America Native Plant

Mountain Threadplant

Botanical name: Nemacladus montanus

USDA symbol: NEMO

Life cycle: annual

Habit: forb

Native status: Native to the lower 48 states  

Mountain Threadplant: A Delicate California Native Worth Discovering If you’re drawn to California’s most unique and delicate native wildflowers, mountain threadplant (Nemacladus montanus) might just capture your gardening heart. This charming little annual brings an ethereal quality to native plant gardens with its wispy, thread-like stems and tiny star-shaped flowers ...

Rare plant alert!

Region: Conservation status by state

Status: S2S3: Status is uncertain but is somewhere between the following rankings: Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 6 to 20 occurrences or few remaining individuals (1,000 to 3,000) ⚘ Vulnerable: Either very rare and local throughout its range, found only in a restricted range (even if abundant at some locations), or factors are making it vulnerable to extinction. Typically 21 to 100 occurrences or between 3,000 and 10,000 individuals ⚘

Mountain Threadplant: A Delicate California Native Worth Discovering

If you’re drawn to California’s most unique and delicate native wildflowers, mountain threadplant (Nemacladus montanus) might just capture your gardening heart. This charming little annual brings an ethereal quality to native plant gardens with its wispy, thread-like stems and tiny star-shaped flowers that seem to float in mid-air.

What Makes Mountain Threadplant Special

Mountain threadplant is a true California original—a native forb that grows naturally only within the Golden State’s borders. As an annual plant, it completes its entire life cycle in just one growing season, making every appearance a special event in the garden. Don’t let its delicate appearance fool you though; this little survivor has adapted perfectly to California’s challenging mountain environments.

The plant earns its common name honestly, with incredibly thin, branching stems that create an almost web-like appearance. Tiny white to pale pink flowers, each no bigger than a pencil eraser, dot these thread-like branches from late spring through early summer.

Where Mountain Threadplant Calls Home

This rare gem is found exclusively in California, where it grows naturally in the state’s mountainous regions. You’ll find it clinging to rocky slopes and gravelly hillsides, often in areas where few other plants dare to grow.

Important Conservation Note

Before you fall head over heels for this plant, there’s something important to know: mountain threadplant has a conservation status of S2S3, meaning it’s considered rare and potentially vulnerable. If you’re interested in growing this species, it’s crucial to source seeds or plants only from reputable native plant nurseries that practice ethical collection methods. Never collect from wild populations.

Why Grow Mountain Threadplant?

While mountain threadplant might not win any awards for showy blooms, it offers several compelling reasons to include it in your native plant collection:

  • Supports native biodiversity and helps preserve a rare California species
  • Attracts small native pollinators that larger flowers might miss
  • Adds delicate texture and movement to rock gardens
  • Requires minimal water once established
  • Perfect for xerophytic (dry) landscape designs

Garden Design Ideas

Mountain threadplant shines in specialized garden settings where its subtle beauty can be appreciated up close. Consider it for:

  • Rock gardens where it can nestle between stones
  • Native plant demonstrations or educational gardens
  • Xerophytic landscapes that celebrate California’s natural heritage
  • Container gardens where you can control growing conditions precisely

Growing Conditions and Care

Success with mountain threadplant comes down to mimicking its natural mountain habitat. This means providing:

  • Excellent drainage: Rocky, sandy, or gravelly soils work best
  • Full sun exposure: At least 6-8 hours of direct sunlight daily
  • Minimal water: Once established, water sparingly if at all
  • USDA Zones 8-10: Best suited for California’s mediterranean climate

Planting and Care Tips

Growing mountain threadplant successfully requires patience and attention to detail:

  • Start from seed sown in fall to allow for natural winter stratification
  • Prepare planting areas with extra drainage material like coarse sand or small gravel
  • Water lightly during germination, then reduce watering as plants establish
  • Allow plants to self-seed for future generations
  • Avoid fertilizers, which can harm this adapted-to-poor-soils species

Wildlife and Pollinator Benefits

Don’t underestimate the ecological value of mountain threadplant’s tiny flowers. These small blooms are perfectly sized for California’s smaller native pollinators, including tiny native bees and beneficial insects that might be overlooked by showier plants. By growing mountain threadplant, you’re supporting the full spectrum of your local ecosystem.

The Bottom Line

Mountain threadplant isn’t for every gardener or every garden. Its subtle beauty and specific growing requirements make it best suited for dedicated native plant enthusiasts who appreciate rare and unusual species. However, for those willing to provide the right conditions and source plants responsibly, mountain threadplant offers the satisfaction of growing a truly special piece of California’s natural heritage.

Remember, with great rarity comes great responsibility. If you choose to grow mountain threadplant, you’re becoming a steward of California’s botanical diversity—and that’s a pretty amazing role to play in your own backyard.

Mountain Threadplant

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Asteridae

Order

Campanulales

Family

Campanulaceae Juss. - Bellflower family

Genus

Nemacladus Nutt. - threadplant

Species

Nemacladus montanus Greene - mountain threadplant

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA