Amsonia tabernaemontana: Growing And Caring For The Blue Star Plants

Amsonia tabernaemontana [am-SO-nee-uh, tab-er-nay-MON-tah-nuh] is a native herbaceous perennial growing most frequently in rich, open woods and thickets.

Native to several states in North America including Texas, Florida, Missouri, Illinois, and New York.

It’s part of the dogbane family Apocynaceae along with spring flowering Mandevilla and the Adenium Desert Rose Plant.

Flowering Blue Star plant (Amsonia)

They were separated as a genus in 1788.

You may hear it by its common names:

  • Blue Dogbane
  • Blue Star
  • Eastern Bluestar
  • Willowleaf
  • Willow Amsonia
  • Woodland Bluestar

Bluestar Amsonia Tabernaemontana Care

Size and Growth

Blue Star plants grow up to 2′ – 3′ feet tall and 2′ – 3′ feet wide, but the size mostly depends on the growing conditions.

They tend to grow in shrub-like, small, and tidy clumps.

The plants begin to bloom from early summer to late spring.

Flowering and Fragrance

It’s an erect, clump-forming plant with star-shaped pale blue flowers and basic green foliage color.

Each flower is small but blooms in fluffy clusters.

They are showy plants staying for up to several weeks.

They have a delicate, sweet scent.

It’s bloom time is March, April, and May.

The other bloom colors include purple with notes of yellow-orange anthers.

The crowded narrow leaves turn golden-yellow for its fall color.

The prominent light blue flower color is always dainty or pale in appearance.

Light and Temperature

The Amsonia tabernaemontana grows in the United States (USDA) Hardiness Zones 3 – 9 but can survive in different climates and conditions.

The flower thrives in partial shade and even in full sun. It’s drought tolerant.

Indoors, the Amsonia can grow from a bare root at a temperature of 55° – 60° degrees Fahrenheit (13° C – 16° C).

For retail, a temperature of 50° – 60° degrees Fahrenheit (10° C – 16° C) can create compact, sturdy plants.

Watering and Feeding

Use a water-soluble fertilizer when the new leaves begin to emerge.

At a rate of 50-100 ppm nitrogen constant liquid feed whenever you water the plant.

Fertilizer needs to be slow-released at an average rate so it applies evenly to the plant.

Moisture should be moderate, and well-drained soil is needed.

Plants should be allowed to dry between each watering.

Discontinue watering in the fall.

Soil and Transplanting

The Blue Star needs full sun if there’s a lot of wet soil moisture.

Otherwise, the plant needs part shade but too much and the plant will flop or sprawl.

It grows anywhere as long as the soil has a pH of 6.2-7.

Give the soil a thick layer of organic mulch like bark, shredded leaves, or pine straw for it to thrive.

If the soil is sandy or has clay, work in as much well-rotted manure or compost into the soil at a depth of 6″ – 8″ inches.

To transplant, water the plant 24 hours before digging it up.

Cut the stems and foliage to 6″ inches and plant in new holes.

Fill the hole with loose moist soil and lightly tamp down the ground to create air pockets.

Thoroughly water after transplanting is complete.

Grooming and Maintenance

After flowers begin to fade, feed the plant compost and cut down the height of the plant to 10″ inches.

This encourages new growth and leaves enough energy for the roots to develop again.

Deadheading isn’t necessary, so to keep your Blue Star sturdy, you will have to frame with other sturdy plants on either side.

It will keep the plants upright and allow the seed pods to remain.

The Blue Star plant will eventually get fairly wide and bush out.

They aren’t invasive though and only spread to a couple of feet.

Even when grown in full sun this plant rarely requires pruning or staking.

How to Propagate Blue Dogbane

The Blue Star can be propagated by seed and division.

Seed germination can be irregular and slow since different varieties of Amsonia emerge through each seeding; the new plant may not be the same as the parent plant if propagation is via seed.

Eastern Bluestar Pest and Diseases

The occurrence of pests and diseases in the Blue Star is minimal compared to other perennial plants.

Currently, the only pathogen to adversely affect the plant is rust and Mycosphaerella leaf spot.

Ensure the area the plant’s planted in is adequately ventilated to prevent rust.

Routine scouting is enough to spot any pests on the plant.

Suggested Uses for Blue Star

They have landscape uses since their small foliage, and striking color makes them great as an accent plant.

They also have a vase-shaped growth habit which looks great in native plant gardens.

It pairs well with low maintenance rain gardens.

The stems contain a milky sap, dip them in boiling water to seal the stalks and make long-lasting cut flowers.

The Blue Star attracts butterflies, carpenter bees, and hummingbird moths but is deer resistant.

Western Native Americans used the plant as a cure for rattlesnake bites.