Blue Star Blooms: Grow Amsonia Tabernaemontana Easily

With its brief but beautiful blue star-shaped blooms, Blue Star (Amsonia tabernaemontana) is a popular and easy-to-grow perennial. Striking heads of pale blue flowers emerge in late spring and bloom through the warm summer months. What’s more, the willow-shaped leaves can be enjoyed into the fall when they turn a golden yellow. Blue Star flowers also make great companions for various garden designs and layouts. In this article, we’ll take you through every area of growing and caring for Blue Star flowers at home.

How To Grow Blue Star Flowers (Amsonia tabernaemontana)

How to Grow Blue Star (Amsonia tabernaemontana) – The Essentials:

Botanical Name:Amsonia tabernaemontana
Also Known As:Eastern Blue Star, Willow Blue Star, Blue Dogbane, Bluestar
Hardiness Zones:USDA Zones 3 to 9
Flowering Months:May to June
Growing Difficulty:Easy to grow, low maintenance, suitable for novices
Type of Plant:Flowering deciduous perennials
Light Requirements:Likes full sun or some partial shade
Temp & Humidity:Needs a minimum of 50 to 60ºF but thrives in hotter temperatures. Requires low to moderate humidity and is slightly drought-tolerant
Watering Needs:Water when the top of the soil feels mostly dry, about once per week
Soil Preferences:Prefers well-draining  neutral (6 to 7 pH) soils that can stay moist
Feeding:Give a dose of slow-release fertilizer once every one or two weeks once leaves have emerged
Growth Expectations:Grows up to 2 to 3 feet tall and wide
Toxicity:Produces a milky sap that can irritate the skin. Toxic to cats and dogs

How to Grow Blue Star (Amsonia tabernaemontana)

Blue Star (Amsonia tabernaemontana) in bloom

Is Blue Star Considered Easy to Grow?

Blue Star plants are slow growers that can mostly be left to their devices. They need consistently moist soil but can also tolerate light droughts. Their low-maintenance requirements make them easy to grow and ideal for less-experienced gardeners.

The Best Locations to Plant Blue Star Flowers

Depending on regional climates, Blue Star plants thrive in either full sun or light shade. In hotter, drier areas, provide a slightly shady spot for cover from the afternoon sun. Plant the Blue Star in well-draining neutral soil with plenty of nutrients. They can survive in tougher soils but prefer loamy or sandy growing mediums.

What Are the Best Times of Year to Plant Blue Star Flowers?

Blue Star should be planted in early spring or the fall ready for the following season. Flowering begins in May, so the foliage needs a chance to grow before then. Seeds can be sown outdoors in the middle of spring or fall.

Growing Blue Star Plants From Seed Vs Planting Young Nursery Plants

Blue Star plants grow fairly slowly, so growing them from seed will take quite a while. Seeds can be collected from adult plants once the seed pods have dried out. 

If you want to enjoy Blue Star plants more immediately, you can purchase younger plants at nurseries. Once planted, they will reach a decent size in just a couple of years. 

What to Do Before Planting Blue Star Flowers

Blue Star requires nutrient-rich soil to truly thrive. Before planting, mix plenty of compost into the soil, especially in sandy conditions. Provide this in the top six to eight inches of soil. Prepare a layer of organic material to go on top of the soil once planting is complete.

This top layer can be made from bark shavings, mulch, or chopped-up leaves. Aim for at least three inches of mulch. Select a position that provides full sun or partial shade in hotter climates.

If you’re planting your Blue Star as part of a border display, consider its position relative to other plants. Take into account the expected mature height and spread.

What’s the Best Soil for Blue Star Flowers?

The ideal soil composition for Blue Star requires a well-draining medium that still provides plenty of nutrition. The growing medium must also retain some moisture, especially in hotter areas. Loamy or sandy soils are the best possible choices.

The soil should have a neutral pH of between 6.0 and 7.0. Blue Star can also handle slightly poorer mediums that are chalky or stony.

How to Plant Blue Star Flowers

When planting a young or mature Blue Star plant, dig a hole about twice the size of the root ball. Place the plant in the hole, covering it with compost and soil. Add an upper layer of mulch and water the plant thoroughly. Allow for 20 to 30 inches between each Blue Star plant.

Blue Star seeds can be sown indoors or outside. If you sow them indoors, initiate the process two or three months before you plan to plant them. The seeds take four to six weeks to germinate. Maintain the seedlings at a temperature between 58 and 65ºF (14 to 18ºC).

Plant the seedlings out once the final frost has passed in early spring. Any seeds sown outdoors must be protected from cold weather.

Blue Star Flower Light Preferences

A close shot of blue star flowers against green leaves and foliage

Blue star plants are adaptable to lighting conditions and thrive in direct sun or partial shade. Exposure to full sun creates the most potent flowers, but it can be detrimental in hotter climates. If you live in an area with higher temperatures, provide shade for the Blue Star during the afternoon.

Blue Star Temperature & Humidity Preferences

Temperature: As American natives, Blue Star can handle most temperatures nationwide. However, they prefer warmer temperatures whenever possible. Minimum temperature should range from 55 to 65ºF (12.7 to 18ºC).

Humidity: Blue Star does best when its soil is kept consistently moist, but it is slightly drought-tolerant. Low to mid humidity suits these plants well.


How to Care For Blue Star (Amsonia tabernaemontana)

Blue Star (Amsonia tabernaemontana) producing tall spikes of tiny flowers in a green oranmental garden

Watering Blue Star

Blue Star needs consistent moisture in its soil. Water it approximately once per week or when the top of the growing medium feels dry. Water more frequently in hotter climates and less frequently in winter.

How, When, and Why to Fertilize

For the best blooms and foliage, start feeding Blue Star once the leaves have emerged in early spring. Use a slow-release fertilizer that can be diluted with water. Feed once every one or two weeks.

Pruning & Cutting Back

As part of its low-maintenance needs, Blue Star doesn’t require much pruning. Deadhead any blooms that have expired to encourage fresh flowers. Productive plants tend to droop under the weight of their blooms. Support them with a cane or stake.

Once it has stopped flowering, prune the Blue Star back to about ten inches high in late fall. This helps create bushier foliage for next year.

Propagation

As clump-growing plants, propagating Blue Star is pretty straightforward. Dig up the parent plant in the spring and split it into clumps. Each clump should have its own root system. Plant these new Blue Stars with some of the growing medium from the parent plant mixed with fresh compost.

Blue Star can also be propagated through seeds, harvested from the seed pods in late summer and fall.

Overwintering Blue Star Flowers

Because they are native to the United States, Blue Star plants can survive winter in most areas. In warmer regions especially, no winter protection is necessary. 

In Zones 3 or 4, Blue Star plants grown in containers can be overwintered in garages or greenhouses. Seedlings must be protected from the winter chill using a greenhouse or cold frame.

When and How to Repot Blue Star Plants Grown in Containers

Blue Star is a gradual grower, so repotting plants grown in containers isn’t required too often. Young plants purchased from nurseries should be planted into the ground or repotted into a larger container. 

This is best performed in the spring. Plant the specimen into a container with plenty of rich, well-draining growing medium. Allow for at least 20 to 30 inches of spreading space.


Common Blue Star Problems & How to Treat Them

A cluster of flowering Blue Star plants

Blue Star plants are surprisingly hardy and don’t suffer from many common garden diseases or pests. Here are a couple of problems to look out for:

Overwatering and Underwatering

While Blue Star requires consistent moisture in its soil, too much water can cause problems such as root rot. Not providing enough water, especially in drier climates, leads to drooping stems or wilted foliage. Only water when the top of the growing medium feels dry.

Too Much Light

In most climates, Blue Star loves full sun. But in exceptionally hot climates, too much sun can scorch the leaves. Provide some afternoon shade to protect the plant.

Common Pests & Diseases

Rust diseases are caused by fungus. These ailments can show up as pustules or spots on the foliage. Removing affected leaves immediately and maintaining optimal growing conditions can help prevent rust diseases.


Essential Tools to Have Around

A selection of garden tools
  • Gardening gloves to avoid the irritating sap
  • Secateurs
  • Watering can
  • Trowel

Growing Blue Star (Amsonia tabernaemontana) FAQs:

Do Blue Star flowers come back every year?

Blue Star plants are flowering perennials and produce flowers each year from May into June.

Do Blue Star flowers attract bees?

Blue Star flowers are great for tempting pollinators such as bees, butterflies, and hummingbirds into the garden.

Do Blue Star flowers bloom in the first year?

If you’re growing Blue Star plants from seed, they won’t bloom in their first year.

Do you deadhead Blue Star (Amsonia tabernaemontana)?

Deadhead Blue Star plants during their brief flowering season to get as many blooms as possible.

Where is Blue Star (Amsonia tabernaemontana) native to?

Blue Star is indigenous to North America, especially the eastern and central United States.

Is Blue Star (Amsonia tabernaemontana) considered invasive?

Blue Star grows in slow-growing clumps and won’t be at risk of taking over a garden. These plants are not considered invasive.

Wrap Up

Despite their brief burst of light blue flowers, Blue Star plants are excellent additions to any garden. Their dark green foliage can be enjoyed into the fall, where it then turns a glorious golden-yellow. These plants require minor maintenance and are a great choice for novice gardeners.


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