Japanese aster 'Blue Star'

Questions about Japanese aster 'Blue Star'

Does Japanese aster 'Blue Star' need sun or shade?

Japanese aster 'Blue Star' grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).

It wants ordinary well-drained soil, of average fertility, and a good soak in dry spells. Once settled in, it stands drought.

What zones does Japanese aster 'Blue Star' grow in?

USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).

Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.

When does Japanese aster 'Blue Star' flower in my zone?

In zone 5 it flowers late June to mid September. As a summer flower it moves about half a week for every zone: earlier where it is warmer.

Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.

How far apart should Japanese aster 'Blue Star' be planted?

18 in (45 cm) apart, from the middle of one plant to the middle of the next. That is about its full width, so each plant keeps its own outline.

It grows 18 in (45 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many Japanese aster 'Blue Star' plants do I need?

At 18 in apart, set out in staggered rows:

• 5 to fill 10 square feet (about 1 m²)
• 7 for a single row 10 ft (3 m) long
• 17 to fill a 4 × 8 ft bed on its own

In a mixed border, plant it as a group of three or five, with a second group further along in the other number.

In the bed above, the planner used three in one group.

Is Japanese aster 'Blue Star' poisonous to dogs and cats?

No toxicity is recorded for dogs, cats, horses or people, according to NC State Extension.

"Not toxic" is not "edible": a pet that eats a lot of any plant can be sick.

Is there a native plant like Japanese aster 'Blue Star'?

Japanese aster 'Blue Star' comes from SE Siberia to Northern China and Central & Southern Japan. These North American natives come closest to doing its job:

• Stokes' aster: the same job in a bed and the same size; flowers late June to mid August, blue, purple or white, not lavender.
• Blanket flower 'Mesa Yellow': the same job in a bed, the same size and the same flowering time; yellow, not lavender, wants dry soil.
• Goldenrod 'Golden Fleece': the same job in a bed and the same size; flowers late August to early October, yellow, not lavender.

Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.

Do deer eat Japanese aster 'Blue Star'?

Mostly not. NC State lists it as resistant to deer and rabbits. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.

What flowers after Japanese aster 'Blue Star'?

Japanese aster 'Blue Star' is over by mid September. These start as it finishes and carry the same spot on, so it never goes flat:

• Garden chrysanthemum: from mid September to late October, 24 in tall.
• October daphne: from mid September to late October, 8 in tall, to stand in front of it and cover its fading stems.
• Meadow saffron: from mid September to mid October, 6 in tall, to stand in front of it and cover its fading stems.

What does Japanese aster 'Blue Star' look like in winter?

Japanese aster 'Blue Star' dies down to the ground and there is nothing to see until spring. The old stems can be cut in autumn, or left until spring as shelter for overwintering insects.

Is Japanese aster 'Blue Star' good for bees and butterflies?

Japanese aster 'Blue Star' is visited by bees and butterflies.