How to Grow and Care For Amsonia Tabernaemontana
Image by A. Barra from wikipedia
Amsonia flowers are native to North America and have a lengthy season of interest. It appears in the spring with rounded, tidy mounds of willowy foliage. The plant gets its common name, “blue star,” from loose clusters of half-inch (1 cm), star-shaped, blue blossoms that appear in late spring and early summer. They are very adaptable in terms of garden design because of the airy but substantial texture of the foliage, which makes a great foil for almost any other plant. The foliage’s brilliant yellow fall colour is an added bonus.
Although size will vary depending on the variety you are growing and the growing environment, most blue star varieties will reach heights and widths of about 2-3 feet. They typically grow in neat, little shrubby clumps. The leaves are lance-shaped, 3–4 inches long, and have a distinct mid-rib. With each species, hardiness will change. Most reach at least USDA Hardiness Zones 3-11.
|Botanical Name||Amsonia tabernaemontana|
|Common Name||Blue star, Blue Dogbane, Eastern blue star, Arkansas amsonia, Hubricht’s amsonia, Willow Amsonia, Woodland Bluestar|
|Mature Size||Roughly 2-3 feet tall and wide.|
|Sun Exposure||Both full sun and some shade|
|Soil Type||Wet to moist, sandy soils|
|Bloom Time||From early summer to late spring|
|Flower Color||Blue, purple, white|
|Hardiness Zones||Zone 3-9 (USDA)|
|Native Area||North America|
|Toxicity||Toxic to people and pets|
Amsonia Plant Care
Amsonia favours full sun and soils that are consistently moist. If not, plant it in bright to partially shaded areas. The plants sprawl or flop open when they are in too much shade. Humus-rich soil and a substantial layer of organic mulch are required for the best Amsonia growing conditions.
Work in as much compost or well-rotted manure as possible to a depth of 6 to 8 inches when growing Amsonia plants in sandy or clay soil (15-20 cm.). Spread at least 3 inches (8 cm) of organic mulch around the plants, such as pine straw, bark, or shredded leaves. As it decomposes, the mulch prevents water evaporation and adds nutrients to the soil. After the flowers fade, feed each plant a shovelful of compost and prune shade plants to a height of 10 inches (25 cm.).
Never let the soil dry out, especially if the plants are growing in direct sunlight. When the soil’s surface feels dry, water slowly and deeply to allow the soil to absorb as much moisture as possible without becoming soggy. In the fall, stop watering.
Planting your blue star in full sun will result in more flowers, but the plants can tolerate partial shade and may even grow better in hot, dry climates.
Amsonia plants prefer a neutral soil pH of 6.2-7.0, but will grow almost anywhere, including poor soil. They dislike prolonged periods of drought, but once established, Blue star plants can withstand brief periods of drought.
Bluestars must drink plenty of water throughout their lives. They can be drought tolerant in cooler climates, happily skipping a day or three without water. However, in hot climates, your Amsonia soil should never be exposed to prolonged periods of dryness, as this will result in heat stress.
Light and Temperature
The Amsonia tabernaemontana grows in USDA Hardiness Zones 3 – 9, but it can survive in a variety of climates and conditions. The flower grows well in both partial shade and full sun. It is drought resistant.
Indoors, the Amsonia can grow from a bare root at temperatures ranging from 55° to 60° Fahrenheit (13° to 16° Celsius). A temperature of 50° – 60° F (10° C – 16° C) can produce compact, sturdy plants for retail.
Bluestars can thrive in poor quality soil and under harsh conditions, but that doesn’t mean they shouldn’t be fed on a regular basis. Fertilizing is especially important during the early stages of your Bluestar’s life. When the first few leaves appear, amend your soil with a slow-release balanced fertiliser. This will supply the plant with everything it requires during the flowering season. Alternatively, start with a nitrogen-rich fertiliser in the spring and gradually transition to a phosphorus and potassium-rich fertiliser to promote flowering.
Pests and diseases are the least of your concerns when it comes to planting Amsonias. Because of their slightly toxic sap, these plants are surprisingly resistant to most common pests and diseases, including deer.