Arkansas bluestar

Arkansas bluestar: how do you recognise it?

Habit

Rounded, bushy clump 80–90 cm tall and as wide, with many upright stems; it looks like a small shrub.

Leaves

Very narrow and thread-like, up to 8 cm long, crowded along the stems; fresh green, turning golden to orange-yellow in autumn.

Flower

Small, pale blue stars about 1.5 cm across in loose clusters at the stem tips, in May–June.

Fruit

Slender, narrow pods held upright at the tips of the stems.

Roots

Deep and tough: they make it drought-tolerant, but an old clump is hard to divide.

Milky sap

Broken stems release a white milky sap that can irritate the skin.

Flowering: May–June · Plants: March–May and September–October · Pruning: March and June

Why grow it?

• Spectacular golden autumn colour, one of the finest of all perennials.
• The fine, feathery foliage gives a soft texture all summer, like a small shrub.
• Pale blue star flowers in May–June that attract bees.
• Drought-tolerant and long-lived: once established it needs hardly any work.
• Little troubled by slugs or other pests.

Arkansas bluestar: where does it grow best?

• Full sun gives the densest clump and the best autumn colour; partial shade is fine, but the plant becomes looser.
• Sand, loam or clay, acid to neutral: it is not fussy, as long as the soil is not waterlogged.
• Dry to moderately moist; once established it copes well with drought.
• Allow 80–90 cm of space per plant, as a specimen or in a group.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Acid or neutral

Moisture

Dry or normal

Size

0.9 m tall, 0.9 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Coneflower: Pink and purple summer flowers beside the fine foliage.
• Michaelmas daisy: Purple and blue next to the golden autumn colour.
• Showy stonecrop: Broad, red-brown flower heads that stand out against the fine foliage in autumn.
• Switchgrass: An ornamental grass with the same prairie feel and warm autumn colour too.
• Catmint: A low, blue edging at the front, also drought-tolerant.

Arkansas bluestar: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October.
2. Dig a hole twice as wide as the pot and loosen the soil deeply.
3. Set the plant at the same depth as in the pot and firm the soil.
4. Keep 80–90 cm between plants: a young plant looks small, but it fills out considerably within a few years.
5. Water in well straight away and regularly in dry spells during the first season.
6. A thin mulch of compost or wood chips keeps weeds down while it establishes.

Care

Watering

In dry spells during the first year. After that only during an exceptionally long drought.

Feeding

Not needed: soil that is too rich makes the stems floppy.

Patience

It grows slowly for the first 2–3 years and then gets better every year.

Support

Usually unnecessary in sun. In partial shade you can cut it back by a third after flowering to keep it compact.

Moving

Best avoided: leave it undisturbed.

Tip: Plant it where the low autumn sun shines through it: the golden foliage then glows like a flame. Give it 2–3 years; after that it will be one of the finest plants in your garden for many years.

Arkansas bluestar: when to prune it?

Pruning months: March and June.

When: The main cut is in March: remove the old stems before the new shoots appear. If it gets too loose, you can shorten it by a third in June, after flowering.

How:

• Leave the stems standing in autumn so you can fully enjoy the golden colour.
• In March, cut everything back to 5–10 cm above the ground.
• Cutting back after flowering does not cost you the autumn colour: the plant regrows and stays more compact.
• Wear gloves because of the milky sap.

Caution: The white milky sap can irritate the skin: wear gloves and do not rub your eyes.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April, lift a clump and split it with a sharp spade. Young clumps divide more easily than old, tough ones.

Cuttings

In May–June, take 8–10 cm cuttings from young shoots and insert them in moist cutting compost. Wear gloves because of the milky sap.

Seed

Sow in autumn in a pot left outdoors: the seed needs a cold spell. Seedlings grow slowly.

Arkansas bluestar: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection is needed in Belgium.
• Leave the stems until March: even after the leaves have fallen they give structure.
• A large pot is possible, but make sure drainage is good and stand it against a wall in winter.

Diseases and pests

• Flopping: In too much shade or soil that is too rich, the clump falls open. Move it to a sunnier spot, do not feed it and cut it back by a third after flowering.
• Slow start: In its first year it seems to do very little. That is normal: it puts its energy into the roots first.
• Skin irritation: Red, itchy skin after pruning, caused by the milky sap. Wear gloves and long sleeves.
• Root rot: In waterlogged soil the clump rots in winter. Plant it where water does not stand.

Through the year

• March: Cut down old stems. Plant.
• April: Plant or divide. The new shoots appear.
• May: Flowering begins. Take cuttings.
• June: Flowering. Afterwards, cut back by a third if needed.
• July: Water young plants in dry spells.
• September: Plant.
• October: Golden autumn colour. Plant.
• November: Autumn colour. Leave the stems standing.

Edible and useful

Not edible. The white milky sap of amsonia is poisonous and irritates the skin and eyes; eating it causes vomiting, stomach ache and diarrhoea. The plant belongs to the same family as oleander and periwinkle. Wear gloves when cutting it back in autumn and when dividing, do not rub your eyes and wash your hands afterwards. Keep children and animals that chew plants, such as cats, dogs and rabbits, away, and do not throw the trimmings into a run or field. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• Amsonia belongs to the dogbane family, like periwinkle and oleander: hence the milky sap.
• The species name honours Leslie Hubricht, the American naturalist who collected the plant in the 1940s.
• In the wild it grows only in a small area: the Ouachita Mountains of Arkansas and Oklahoma.